Tactical development on the Western Front in 1917

In 1917 the armies on the Western Front continued to change their fighting methods due to the consequences of increases in fire-power, greater numbers of automatic weapons, the decentralisation of authority and the integration of specialised branches, equipment and techniques into the traditional structures of infantry, artillery and cavalry. Tanks, railways, aircraft, lorries, chemicals, concrete and steel, photography, wireless and advances in medical science increased in importance in all of the armies, as did the influence of the material constraints of geography, climate, demography and economics. All of the armies encountered growing manpower shortages, caused by the need to replace the losses of 1916 and by the competing demands for labour of civilian industry and agriculture. The consequences of dwindling manpower were particularly marked in the German and French armies, which made considerable changes in their methods during the year, with the object of simultaneously pursuing military–strategic objectives and limiting casualties.

The French army began the year with a return to the strategy of decisive battle, using the methods pioneered at the Battle of Verdun in December 1916, to break through the German defences on the Western front and return to manoeuvre warfare (bewegungskrieg) but ended the year recovering from the disastrous result. The German army attempted to avoid the high infantry losses of 1916 by withdrawing to new deeper and dispersed defences. Defence in depth was intended to nullify the Allies' growing material strength (particularly in artillery) and succeeded in slowing the growth of Anglo-French battlefield superiority. The British army continued its evolution into a mass army capable of imposing itself on a continental power, took on much of the military burden, borne by the French and Russian armies since 1914 and left the German army resorting to expedients, to counter the development of its increasingly skillful use of fire-power and technology. During 1917 the British army also experienced the manpower shortages that hampered the French and Germans and then at Cambrai in December, encountered the revitalising effect on the German army of reinforcements from Russia.

Background
Hindenburg and Ludendorff replaced Chief of the General Staff Erich von Falkenhayn at the end of August 1916 during "the most serious crisis of the war". On 2 September the new leadership ordered a strict defensive at Verdun and the dispatch of forces from there to reinforce the Somme and Rumanian fronts. Hindenburg and Ludendorff visited the Western front and held a meeting at Cambrai on 8 September with the army group and other commanders, at which the gravity of the situation in France and the grim prospects for the new year were debated. Hindenburg and Ludendorff had already announced a reconnaissance on 6 September for a new, shorter line behind the Noyon salient. On 15 September a defensive strategy was announced except for Rumania and Generalfeldmarschall Rupprecht (commander of the northernmost army group on the Western front) was instructed to prepare a new line, Arras–St. Quentin–Laon–Aisne river. The new line across the base of the Noyon salient would be about thirty miles (50 km) shorter and was to be completed in three months. These defences were planned with the experience gained on the Somme which showed a need for much greater defensive depth and many small shallow concrete "Mebu" (Mannschafts-Eisenbeton-Unterstände) shelters, rather than elaborate entrenchments and deep dug-outs, which had become man-traps; work was ordered to begin on 23 September. Two trench lines about 200 yd apart were dug as an outpost line (Sicherheitsbesatzung) and a main line of resistance (Hauptverteidigungslinie) on a reverse slope, (Hinterhangstellung) behind fields of barbed wire up to 100 yd deep. Concrete machine-gun nests and Mebu shelters were built either side of the main line, with artillery observation posts built farther back to overlook it.

On 31 August Hindenburg and Ludendorff had begun the expansion of the army to 197 divisions and of munitions production in the Hindenburg Programme, necessary to meet demand after the vast expenditure of ammunition in 1916 (on the Somme in September, 5,725,440 field artillery shells and 1,302,000 heavy shells were fired) and the anticipated increase in artillery use by the Allies in 1917. It was intended that the new defensive positions being built would contain any Allied breakthrough and also give the German army the choice of a deliberate withdrawal, to dislocate an expected Allied offensive in the new year. Over the winter of 1916–1917 the wisdom of a deliberate withdrawal was debated and at a meeting on 19 December, called after the 15 December débâcle at Verdun, the possibility of a return to the offensive was also discussed. With a maximum of 21 divisions expected to be available by March 1917, a decisive success was considered impossible. Ludendorff continued to vacillate but in the end, the manpower crisis and the prospect of releasing thirteen divisions by a withdrawal on the Western Front, as far back as the new Siegfriedstellung (Hindenburg Line) overcame his desire to avoid the tacit admission of defeat it represented. The Alberich Bewegung (manoeuvre) was ordered on 16 March 1917, although a withdrawal of three miles on a fifteen mile front had been carried out on 22–23 February, in the salient between Bapaume and Arras, which had been formed by the Allied advance on the Somme in 1916; which had been caused by the renewal of pressure by the British Fifth Army, as soon as weather permitted in January 1917, which had advanced five miles on a four-mile front up the Ancre valley.

German defensive preparations in early 1917
When Hindenburg and Ludendorff took over from Falkenhayn on 28 August 1916, the pressure being placed on the German army in France was so great that new defensive arrangements, based on the principles of depth, invisibility and immediate counter-action were resorted to, as the only means by which the growing material strength of the French and British armies could be countered, when a large portion of the German army was operating in Russia. Instead of fighting the defensive battle in the front line or from shell-hole positions near it, the main fight was to take place behind the front line, out of view and out of range of the attackers' field artillery. Die Führung in der Abwehrschlacht (Conduct of the Defensive Battle) was published on 1 December 1916. The new manual laid down the organisation which would allow the mobile defence of an area, rather than the rigid defence of a trench line. Defensive positions necessary for the new method were defined in Allgemeines über Stellungsbau (Principles of Field Position Construction).

Defensive battle methods codified
In Grundsätze für die Führung in der Abwehrschlacht of 1 December 1916, unyielding defence of ground regardless of its tactical value, was replaced by the defence of positions suitable for artillery observation and communication with the rear, where an attacking force would "fight itself to a standstill and use up its resources while the defenders conserve[d] their strength". Defending infantry would fight in areas, with the front divisions in an outpost zone up to 3000 yd deep behind listening posts, with the main line of resistance placed on a reverse slope, in front of artillery observation posts kept far enough back to retain observation over the outpost zone. Behind the main line of resistance was a Grosskampfzone (battlezone), a second defensive area 1500 - 2500 yd deep, sited as far as possible on ground hidden from enemy observation while in view of German artillery observers. A rückwärtige Kampfzone (rear battle zone) further back was to be occupied by the reserve battalion of each regiment.

Field fortification codified
Allgemeines über Stellungsbau (Principles of Field Fortification) was published in January 1917 and by April an outpost zone (Vorpostenfeld) held by sentries had been built along the Western Front. Sentries could retreat to larger positions (Gruppennester) held by Stosstrupps (five men and an NCO per Trupp) who would join the sentries to recapture sentry-posts by immediate counter-attack. Defensive procedures in the battlezone were similar but with greater numbers. The front trench system was the sentry line for the battlezone garrison, which was allowed to move away from concentrations of enemy fire and then counter-attack to recover the battle and outpost zones; such withdrawals were envisaged as occurring on small parts of the battlefield which had been made untenable by Allied artillery fire, as the prelude to Gegenstoss in der Stellung (immediate counter-attack within the position). Such a decentralised battle by large numbers of small infantry detachments would present the attacker with unforeseen obstructions. Resistance from troops equipped with automatic weapons, supported by observed artillery fire, would increase the further the advance progressed. A school was opened in January 1917 to teach infantry commanders the new methods.

Given the Allies' growing superiority in munitions and manpower, attackers might still penetrate to the second (artillery protection) line, leaving in their wake German garrisons isolated in Widerstandsnester, (resistance nests, Widas) still inflicting losses and disorganisation on the attackers. As the attackers tried to capture the Widas and dig in near the German second line, Sturmbattalions and Sturmregimenter of the counter-attack divisions would advance from the rückwärtige Kampfzone into the battlezone, in an immediate counter-attack, (Gegenstoss aus der Tiefe) if this failed the counter-attack divisions would take their time to prepare a methodical attack, if the lost ground was essential to the retention of the main position. Such methods required large numbers of reserve divisions ready to move to the battlefront. The reserve was obtained by creating 22 divisions by internal reorganisation of the army, bringing divisions from the eastern front and by shortening the western front, by withdrawing to the base of the Noyon salient in Operation Alberich. By the spring of 1917 the German army in the west had a strategic reserve of 40 divisions.

Somme (1916) experience codified
"Experience of the German First Army in the Somme Battles", (Erfahrungen der I Armee in der Sommeschlacht) was published on 30 January 1917. Ludendorff's new defensive methods had been controversial; during the Battle of the Somme in 1916 Colonel von Lossberg (Chief of Staff of the First Army) had been able to establish a line of "relief" divisions (Ablösungsdivisionen), with the reinforcements from Verdun which began to arrive in September. In his analysis of the battle, Lossberg opposed the granting of discretion to front trench garrisons to retire, as he believed that manoeuvre did not allow the garrisons to evade Allied artillery fire, which could blanket the forward area and invited enemy infantry to occupy vacated areas unopposed. Lossberg considered that spontaneous withdrawals would disrupt the counter-attack reserves as they deployed and further deprive battalion and division commanders of the ability to conduct an organised defence, which the dispersal of infantry over a wider area had already made difficult. Lossberg and others had severe doubts as to the ability of relief divisions to arrive on the battlefield in time to conduct an immediate counter-attack (Gegenstoss) from behind the battlezone and wanted the Somme practice of fighting in the front line to be retained and authority devolved no further than the battalion, so as to maintain organizational coherence, in anticipation of a methodical counter-attack (Gegenangriff) after 24–48 hours by the relief divisions. Ludendorff was sufficiently impressed by Lossberg's memorandum to add it to the new Manual of Infantry Training for War.

Sixth Army
General Falkenhausen, commander of the Sixth Army arranged his infantry in the Arras area according to Lossberg and Hoen's preference for a rigid defence of the front-line, supported by methodical counter-attacks (Gegenangriffe) by the "relief" divisions (Ablösungsdivisionen) on the second or third day. Five Ablösungsdivisionen were placed behind Douai, fifteen miles away. The new Hindenburg Line ended at Telegraph Hill between Neuville Vitasse and Tilloy lez Mofflaines, from whence the original system of four lines 75 - 150 yd apart, ran north to the Neuville St. Vaast–Bailleul road. About three miles behind were the Wancourt–Feuchy and to the north the Point du Jour lines, running north from the Scarpe along the east slope of Vimy ridge. The new Wotan Line which extended the Hindenburg position, was built around four miles further back and not entirely mapped by the Allies until the battle had begun.

Just before the battle, Falkenhausen had written that parts of the front line might be lost but the five Ablösung divisions could be brought forward to relieve the front divisions, on the evening of the second day. On 6 April General von Nagel (Chief of Staff) accepted that some of the front divisions might need to be relieved on the first evening of battle but that any penetrations would be repulsed with local immediate counter-attacks (Gegenangriffe in der Stellung) by the front divisions. On 7 April, Sixth Army viewed the imminent British attack as a limited effort against Vimy ridge, preparatory to a bigger attack later, perhaps combined with the French attack expected in mid-April. The construction of positions to fulfil the new policy of area defence had been drastically curtailed, by shortages of labour and the long winter, which affected the setting of concrete. The Sixth Army commanders had also been reluctant to encourage the British to change their plans, if they detected a thinning of the front line and inhibited by the extent of British air reconnaissance, which observed new field works and promptly directed artillery fire on them. The Sixth Army failed to redeploy its artillery, which remained in lines, easy to see and bombard. Work on defences was also divided between maintaining the front line, strengthening the third line and the new Wotan Position (known to the British as the Drocourt–Quéant switch line) further back.

Corps
Corps were detached from their component divisions and given permanent areas to hold under a geographical title on 3 April 1917. The VIII Reserve Corps holding the area north of Givenchy became Gruppe Souchez, I Bavarian Reserve Corps became Group Vimy and held the front from Givenchy to the Scarpe river with three divisions, Group Arras (IX Reserve Corps) was responsible for the line from the Scarpe to Croisilles and Group Quéant (XIV Reserve Corps) from Croisilles to Mœvres. Henceforth, divisions would move into the area and come under the authority of the Corps for the duration of their term, then be replaced by fresh divisions.

Division
Using the new defensive system the 18th Division in the German First Army held an area of the Hindenburg Position, with an outpost zone along a ridge near La Vacquerie and a main line of resistance 600 yd behind. The battlezone was 2000 yd deep and backed onto the Hindenburg Line. The three regiments held sectors with two battalions in the outpost and battlezones and one in reserve, several miles to the rear (this deployment was reversed later in the year). The two battalions were side-by-side, with three companies in the outpost zone and front trenches, one in the battlezone and four or five fortified areas within it, (Widerstandsnester) built of concrete and sited for all-round-defence, held by one or two Gruppen (each of eleven men and an NCO) with a machine-gun each. Three and a half companies remained in each front battalion area for mobile defence; during attacks the reserve battalion was to advance and occupy the Hindenburg Line. The new dispositions doubled the area held by a unit compared to July 1916 on the Somme.

Division attack training codified
The training manual SS 135 replaced SS 109 of 8 May 1916 in December 1916 and marked a significant step in the evolution of the British Expeditionary Force (BEF) into a homogeneous force, well adapted to its role on the Western Front. The duties of army, corps and divisions in planning attacks were standardized. Armies were to devise the plan and the principles of the artillery component. Corps were to allot tasks to divisions, which would then select objectives and devise infantry plans subject to corps approval. Artillery planning was controlled by corps with consultation of divisions by the corps General Officer Commanding, Royal Artillery, (GOCRA) which became the title of the officer at each level of command who devised the bombardment plan, which was coordinated with neighbouring corps artillery commanders by the army GOCRA. Specific parts of the bombardment were nominated by divisions, using their local knowledge and the results of air reconnaissance. The corps artillery commander was to coordinate counter-battery fire and the howitzer bombardment for zero hour. Corps controlled the creeping barrage but divisions were given authority over extra batteries added to the barrage, which could be switched to other targets by the divisional commander and brigade commanders. SS 135 provided the basis for the BEF's operational technique for the rest of 1917.

Platoon attack training codified
The training manual SS 143 of February 1917, marked the end of attacks made by lines of infantry with a few detached specialists. The platoon was divided into a small headquarters and four sections, one with two trained grenade-throwers and assistants, the second with a Lewis gunner and nine assistants carrying 30 drums of ammunition, the third section comprised a sniper, scout and nine riflemen and the fourth section had nine men with four rifle-grenade launchers. The rifle and hand-grenade sections were to advance in front of the Lewis-gun and rifle-grenade sections, in two waves or in artillery formation, which covered an area 100 yd wide and 50 yd deep with the four sections in a diamond pattern, the rifle section ahead, rifle grenade and bombing sections to the sides and the Lewis gun section behind, until resistance was met. German defenders were to be suppressed by fire from the Lewis-gun and rifle-grenade sections, while the riflemen and hand-grenade sections moved forward, preferably by infiltrating round the flanks of the resistance, to overwhelm the defenders from the rear.

The changes in equipment, organisation and formation were elaborated in SS 144 The Normal Formation For the Attack of February 1917, which recommended that the leading troops should push on to the final objective when only one or two were involved but that for a greater number of objectives, when artillery covering fire was available for the depth of the intended advance, fresh platoons should "leap-frog" through the leading platoons to the next objective. The new organisations and equipment gave the infantry platoon the capacity for fire and manoeuvre, even in the absence of adequate artillery support against German defences. To bring uniformity in adoption of the methods laid down in the revised manuals and others produced over the winter, Haig established a BEF Training Directorate in January 1917, to issue manuals and oversee training. SS 143 and its companion manuals like SS 144, provided British infantry with off-the-peg tactics, devised from the experience of the Somme and from French Army operations, to go with the new equipment made available by increasing British and Allied war production and better understanding of the organisation necessary to exploit it in battle.

British offensive preparations
Planning for operations in 1917 began in late 1916. Third Army staff made their propsals for what became the Battle of Arras on 28 December, beginning a process of consultation and negotiation with General Headquarters. Sir Douglas Haig, Commander-in-Chief of the British Expeditionary Force (BEF) studied this draft and made amendments resulting in a more cautious plan for the infantry advance. General Allenby, in command of the Third Army proposed to use Corps mounted troops and infantry, to press ahead beyond the main body, which was accepted by Haig, since the new dispersed German defensive organisation gave more scope to cavalry. Third Army's claims on manpower, aircraft, tanks and gas were agreed and its corps were instructed to make their plans according to SS135 Instructions for the Training of Divisions for Offensive Action of December 1916. Behind the lines (defined as the area not subject to German artillery fire) improvements in infrastructure and supply organisation made in 1916, had led to the creation of a Directorate-General of Transportation (10 October 1916) and a Directorate of Roads (1 December) allowing army headquarters to concentrate on operations.

Allenby and his artillery commander planned a 48-hour bombardment based on the experience of the Somme, apart from its relatively short duration, after which the infantry were to advance deep into the German defences, then move sideways to envelop areas where the Germans had held their ground. The 2,817 guns, 2,340 Livens projectors and 60 tanks massed in the Third and First armies, were deployed in relation to the length of front, the quantity of wire to be cut and availability of the new fuze 106. Guns and howitzers were allotted according to their calibre and the nature of the targets to be engaged. Several barrages were planned for the attack, which deepened the area under bombardment. Great stress was laid on counter-battery fire under a Counter-Battery Staff Officer with the use of sound ranging to find the positions of German artillery.

A short bombardment was overruled by Haig and Allenby's artillery commander was promoted out of the way and replaced by Major-General R. St.C. Lecky, who wanted a longer bombardment, as did Major-General H. Uniacke, loaned by the Fifth Army during Lecky's absence through illness. In conferences with his corps commanders, Allenby used a consultative style at first, encouraging the corps commanders to solicit suggestions from subordinates (Conference, 26 February 1917) but later changed bombardment and counter-battery plans without discussion (2 March) although his instructions to the Cavalry Corps gave the commander freedom of action in liaison with the other corps. During the course of the battle Allenby (Third Army Artillery Instructions No.13, 19 April 1917) recommended that artillery batteries should be set aside to deal with German counter-attacks, which had become more effective as the Germans recovered from the initial shock of the attack, to be linked to the front by wireless and registered on probable German forming-up places. On 19 April Notes on Points of Instructional Value (Third Army No. G.14 66.) was circulated as far as battalions, showing the increased effort being made to address the chronic difficulty in communication once operations commenced.

Matters were similarly settled in First Army further north, which had responsibility for the capture of Vimy Ridge, to form a flank guard to the Third Army. The commander Lieutenant-General Sir Henry Horne maintained a consultative style in contrast to Allenby's move towards prescriptive control. On 18 March the XI Corps commander, Lieutenant-General Haking drew attention to two of his divisions which were holding a four-division front, in response to which Horne explained the vital nature of the attack on the Ridge by I Corps and the Canadian Corps further south. Conferences with the corps commanders on 29 March and 15 April discussed the corps commanders' opinions on the possibility of a German withdrawal, road allocations and catering arrangements for the troops in the line, the vital importance of troops communicating with contact aeroplanes and artillery and the dates by which the corps commanders felt able to attack.

Corps
XVII Corps issued a 56-page plan of "Instructions on which Divisional Commanders are to work out their own plans in detail..." which incorporated experience gained on the Somme and stressed the importance of co-ordinated machine-gun fire, counter-battery artillery fire, creeping barrages, the leapfrogging of infantry units, pauses on objectives and plans to meet German counter-attacks. Mortar and gas units were and delegated to divisional control. Tank operations remained a corps responsibility as they were to conform to an army plan against selected objectives. A Corps Signals Officer was appointed to co-ordinate artillery communications on lines later elaborated in SS 148 Forward Inter-Communication in Battle of March 1917, going into the details of telephone line planning to link units with each other, neighbours and their artillery, along with telegraph, visual signalling, pigeons, power buzzers, wireless, codes and liaison with the Royal Flying Corps (RFC).

Much of the corps planning covered artillery, detailing the guns to move forward behind the infantry and their siting. Artillery liaison officers were appointed to infantry units and field guns and howitzers were reserved to engage German counter-attacks. It was laid down that artillery supporting a neighbouring division was to come under the command of that division. For the first time all artillery was integrated into one plan. Planning for the Battle of Arras showed that command relationships, especially within the artillery (which had evolved a parallel system of command, so that General Officers Commanding, Royal Artillery at corps and division were much more closely integrated) and standardization had become more evident between armies, corps and divisions. Analysis and codification of the lessons of the Somme and the process of supplying the armies, meant that the British Expeditionary Force had become much less dependent on improvisation. Discussion and dissent between army, corps and division was tolerated, although it was not uniformly evident. Staffs were more experienced and were able to use a formula for set-piece attacks, although the means for a higher tempo of operations had not been achieved, because of the artillery's reliance on observed fire, which took time to complete. The loss of communication with troops once they advanced, still left their commanders ignorant of events when their decisions were most needed.

Division
Intelligence Officers were added to divisions, to liaise with headquarters as their units moved forward, to report on progress, to increase the means by which commanders could respond to events. Training for the attack had begun in the 56th Division in late March, mainly practicing for open warfare ("greeted with hilarity") with platoons organised according to SS 143. Instructions from Corps restricted light signals to the artillery to green for "open fire" and white for "increase the range" and gave the strength of battalions and the numbers of officers and men to be left out of battle and formed into a Divisional Depot Battalion. The two attacking brigades returned to the line on 1 April giving them plenty of time to study the ground before the attack on 9 April.

On 15 April during the Battle of Arras, VI Corps forwarded to Allenby a report that a conference of the commanders of the 17th Division, 29th Division and 50th Division and the corps Brigadier-General General Staff (BGGS), had resolved that the recent piecemeal attacks should stop and that larger coordinated actions should be conducted after a pause to reorganise, which Allenby accepted. On 17 April the 56th Division commander objected to an operation planned for 20 April, due to the exhausion of his troops and the division was withdrawn instead, when the VI and VII corps commanders and General Horne, the First Army commander also pressed for a delay. VI Corps delegated the barrage arrangements for the attack on 23 April to the divisions involved, which included variations in the speed of the barrage, to be determined by the state of the ground and reference was made in Third Army Artillery Instructions No.12 (18 April) to SS 134 Instructions on the Use of Lethal and Lachrymatory Shell and an Army memo regarding low flying German aeroplanes, called attention to SS 142 Notes on Firing at Aircraft with Machine Guns and Other Small Arms. Third Army Headquarters also gave its corps permission to delegate command of tanks to divisions for the Second Battle of the Scarpe (23–24 April), discretion over local matters being increasingly left to divisional commanders, with corps retaining control over matters affecting the conduct of the battle in general.

British methodical attacks
After 12 April Haig decided that the advantage gained by the Third and First armies since the attack of 9 April had run its course and that further attacks must resume a methodical character. British intelligence estimated that nine German divisions had been relieved with nine fresh ones. On 20 April, after the commencement of the French attacks of the Nivelle offensive, Haig believed that the German reserve had fallen from 40 to 26 fresh divisions but that thirteen tired divisions were recovering and that there were ten new divisions available for the Western Front. With reliefs due on the French front only about eleven fresh divisions would remain to oppose further British operations, which were conducted until early May.

German defensive changes
The first days of the British Arras offensive saw another German defensive débâcle similar to the one at Verdun on 15 December 1916, despite an analysis of that failure being issued swiftly on 15 December, concluding that deep dug-outs in the front line and an absence of reserves for immediate counter-attacks as the cause of the defeat. At Arras similarly obsolete defences overmanned by infantry, were devastated by artillery and swiftly overrun, leaving the local reserves with little choice but to try to contain further British advances and wait for the relief divisions, which were too far away to counter-attack. Seven German divisions were defeated, losing 15,948 men and 230 guns on 9 April.

Given the two failures and the imminence of the French offensive on the Aisne the term Ablösungsdivision was dropped in favour of Eingreif division, a term with connotations of interlocking and dovetailing, to avoid the impression that they were replacement divisions standing by, rather than reinforcements fundamental to the defence of the battlezones by operating support of the local garrisons of the Stellungsdivisionen. A more practical change was the despatch of Colonel von Lossberg from his post as Chief of Staff of the German First Army, (due to move south to join the armies facing Nivelle's looming offensive) to the Sixth Army to replace Nagel on 11 April. Falkenhausen was sacked on 23 April and replaced by General Otto von Below.

Lossberg made a swift reconnaissance of the Sixth Army area, as the British were attacking Bullecourt at the north end of the Siegfriedstellung (Hindenburg Line). He confirmed the decision made to withdraw from the Wancourt salient and the foot of Vimy Ridge, accepting that a rigid forward defence was impossible given British observation from the ridge. North of the Scarpe the front garrison was given permission to withdraw during British attacks, from the battlezone to its rear edge, where it would counter-attack with the reserves held back there and mingle with retreating British infantry, to evade British observed artillery fire; after dark the German infantry would be redeployed in depth under cover. South of the Scarpe, the loss of Monchy-le-Preux also gave the British observation over German positions. Lossberg mapped a new line beyond the range of British field artillery, to be the back of a new battlezone (the Boiry–Fresnes Riegel). At the front of the battlezone he chose the old third line from Méricourt to Oppy, then a new line along reverse slopes from Oppy to the Hindenburg Position at Moulin-sans-Souci, creating a battlezone 2500 yd deep. A rearward battlezone 3000 yd backed on to the Wotan Line, which was nearing completion.

Despite Lossberg's doubts about elastic defence, the circumstances he found on the Sixth Army front made resort to it unavoidable. With artillery reinforcements arriving, the first line of defence was to be a heavy barrage (Vernichtungsfeuer) on the British front line, at the commencement of a British attack, followed by direct and indirect machine-gun fire on the British infantry as they tried to advance through the German battlezone, followed by infantry counter-attacks by local reserves and Eingreif divisions (if needed) to regain the front position. As the British might try to capture ground north of the Scarpe, using their observation from Vimy ridge over the German positions, Lossberg requested that a new be built from Douai south to the Siegfried II Stellung (Hindenburg support line). In the battlezone between the front line and the Boiry–Fresnes Riegel, Lossberg ordered that digging-in was to be avoided, in favour of the maximum use of invisibility (die Leere des Gefechtsfeldes). Machine-guns were not to be placed in special defended localities as in the Siegfriedstellung but to move among shell-holes and improvised emplacements as the situation demanded. Specialist (Scharf–Schutzen) machine-gun units with 15–20 guns each per division, were moved back to the artillery protective line to act as rallying points, (Anklammerungspunkte) for the front garrison and as the firepower to cover the advance of Eingreif units. Artillery was concealed in the same manner, lines of guns were abolished and guns were placed in folds of ground and frequently moved to mislead British air observation, which was made easier by a run of poor weather. The new deployment was ready by 13 April; the remnants of the original front-line divisions had been withdrawn and replaced by nine fresh divisions, with six more brought into the area as new Eingreif divisions.

Army
Planning the Third Battle of Ypres, 1917

Sir Douglas Haig chose General Hubert Gough, commander of the Fifth Army to command the offensive from the Ypres salient. Gough held his first conference around 24 May, before he moved his headquarters to the Salient. II Corps, XIX Corps, XVIII Corps and XIV Corps were to be under the command of the Fifth Army and IX Corps, X Corps and II Anzac Corps in the Second Army. As early decisions were subject to change, detail was avoided, planners were to draw on "Preparatory measures to be taken by Armies and Corps before undertaking operations on a large scale" of February 1916 and SS 135. It was decided to have four divisions per corps, two for the attack and two in reserve, with staff from the reserve division headquarters taking over before the original divisions were relieved. On 31 May Gough dealt with a letter from the XVIII Corps commander Lieutenant-General Ivor Maxse objecting to dawn attacks, since a later time gave troops more rest before the attack. Maxse also wanted to go beyond the black line (second objective) to the Steenbeek stream, to avoid stopping on a forward slope. Gough replied that he had to consider the wishes of all the corps commanders but agreed with the wisdom of trying to gain as much ground as possible, which Gough felt had not been achieved by the Third Army at Arras.

In 1915 the biggest operation of the British Expeditionary Force (BEF) had been by one army with three corps and nine divisions. In 1916 two armies, nine corps and 47 divisions fought the Battle of the Somme, without the benefit of the decades of staff officer experience, that continental conscript armies could take for granted. Rather than the elaborate plans made to compensate for the limited experience of many staff officers and commanders common in 1916, (the XIII Corps Plan of Operations and Operational Order 14 for 1 July 1916 covered 31 pages excluding maps and appendices) XVIII Corps Instruction No.1 was only 23 pages long and concerned principles and the commander's intent, as laid down in Field Service Regulations 1909. Details had become routine, as more staff officers gained experience, allowing more delegation.

Great emphasis was placed on getting information back to headquarters and making troops independent within the plan, to allow a higher tempo ("The rate or rhythm of activity relative to the enemy".) of operations, by freeing attacking troops from the need to refer back for orders. In the process the corps commanders planned the attack in the framework given by the army commander. Planning in the Second Army followed the same system. In mid-June the Second Army corps were asked to submit their attack plans and requirements to carry them out. When the II Corps boundary was moved south in early July, the Second Army attack became mainly a decoy, except for the 41st Division (X Corps) for which special liaison arrangements were made with II Corps and the covering artillery.

At the end of June, Major-General J. Davidson, Director of Operations at GHQ, wrote a memorandum to Haig in which he claimed that there was "ambiguity as to what was meant by a step-by-step attack with limited objectives" and advocated advances of no more than 1500 - 3000 yd, to increase the concentration of British artillery and operational pauses to allow for roads to be repaired and artillery moved forward. This rolling offensive would need fewer periods of intense artillery fire, which would allow guns to be moved forward ready for the next stage. Gough's reply stressed the need to plan for opportunities to take ground left temporarily undefended and that this was more likely in the first attack: "It is important to recognise that the results to be looked for from a well-organised attack which has taken weeks and months to prepare are great, much ground can be gained and prisoners and guns captured during the first day or two.I think we should certainly aim at the definite capture of the Green Line, and that, should the situation admit of our infantry advancing without much opposition to the Red Line, it would be of the greatest advantage to us to do so."Haig arranged a meeting with Davidson, Gough and Plumer on 28 June where Plumer supported Gough's plan, which Haig accepted. Maxse, Gough's XVIII Corps commander, left numerous sarcastic comments in the margins of his copy of the Davidson memo, to the effect that he was being too pessimistic. Davidson advocated views which were little different to Gough's, except for Gough wanting to make additional arrangements that would allow undefended ground to be captured by local initiative.

Corps
At the conference on 6 June Gough took the view that if the Germans were thoroughly demoralised, it might be possible to advance to parts of the red line on the first day. Maxse and Cavan (XIV Corps) felt that the range of their artillery would determine the extent of their advance and that it would need to be moved forward for the next attack. Gough drew a distinction between advancing against disorganised enemy forces, which required bold action and attacks on organised forces, which needed careful preparation, particularly of the artillery which would take three to seven days. Maxse's preference for a later beginning for the attack was agreed except by Lieutenant-General Herbert Watts, XIX Corps commander. A memorandum was issued summarising the conference in which Gough stressed his belief in the need for front-line commanders to use initiative and advance into vacant or lightly-occupied ground beyond the objectives laid down, without waiting for orders. Relieving tired troops gave time to the enemy, so a return to deliberate methods would be necessary afterwards. Judging the time for this was reserved for the army commander, who would need to rely on the reports of subordinate commanders.

Communication by the Fifth Army corps to their divisions reflected the experience gained at Vimy and Messines, such as the value of aerial photography for counter-battery operations, raiding and the construction of scale models of the ground to be covered, the divisional infantry plans, machine-gun positions, mortar plans and positions, trench tramways, places chosen for supply dumps and headquarters, signals and medical arrangements and camouflage plans. Corps responsibilities were the heavy weapons, the infrastructure and communication. In XIV Corps, divisions were to liaise with 9 Squadron RFC for training and to conduct frequent rehearsals of infantry operations, to give commanders experience in dealing with the unexpected occurrences, which were more prevalent in semi-open warfare.

XIV Corps held a conference of divisional commanders on 14 June and Cavan emphasised the importance of using the new manuals (SS 135, SS 143 and Fifth Army document S.G. 671 1) in planning the offensive. Discussion followed on the means by which the Guards Division and 38th Division were to meet the army commander's intent. The decision to patrol towards the red line was left to the discretion of divisional commanders. An attack of this nature was not a breakthrough operation; the German defensive position Flandern I Stellung lay 10000 - 12000 yd behind the front line and would not be attacked on the first day, nonetheless it was more ambitious than Plumer's earlier plan, which had involved an advance of 1000 - 1750 yd. Notes were later sent to the divisions from the next army conference held on 19 June.

At a later conference held by Gough on 26 June the record (Fifth Army S.G.657 44) was written up as the operation order for the attack of 31 July, in which the final objective for the first day was moved forward from the black to the green line and infiltration envisaged from it towards the red line. Responsibility delegated to the divisions for the attack would revert to corps and Fifth Army when the green line was reached. In Gough's Instruction of 27 June he alluded to Davidson's concern about a ragged front line by reminding the Corps commanders that a "clearly defined" line was needed for the next advance and that control of artillery would be devolved to the corps. Gough issued another memorandum on 30 June summarising the plan and referring to the possibility that the attack would move to open warfare after 36 hours, noting that this might take several set-piece battles to achieve.

XVIII Corps issued Instruction No. 1 on 30 June, describing the intention to conduct a rolling offensive, where each corps would have four divisions, two for the attack and two in reserve, ready to move through the attacking divisions for the next attack. Separate units were detailed for the patrolling to be done once the green line was reached and some cavalry was attached to help them. Divisions were to build strong-points and organise liaison with neighbouring divisions, with these groups given special training over model trenches. Ten days before zero, divisions were to send liaison officers to Corps Headquarters. Machine-gun units were to be under corps control until the black line was reached then devolve to divisions, ready to sweep the Steenbeek valley and cover the advance to the green line by 51st and 39th divisions. Tanks were attached to the divisions under arrangements decided by the divisions and some wireless tanks were made available for XIV Corps. Gas units remained under corps control and a model of the ground was built for all ranks to inspect and it was arranged that two maps per platoon would be issued. Arrangements for air–ground communication went into considerable detail. Aircraft recognition markings were given and flares to be lit by the infantry, when called for by contact aeroplanes was laid down as were recognition marks for battalion and brigade headquarters and dropping stations were created to receive information from aircraft. Ground communication arrangements were made according to the manual SS 148. Appendices covered Engineer work on roads, rail, tramways and water supply; intelligence arrangements covered the use balloons, contact aeroplanes, Forward Observation Officers, prisoners, returning wounded, neighbouring formations, wireless eavesdropping and Corps Observers attached to brigades, who would patrol forward once the black line was reached, to observe the area up to the green line, judge the morale of the Germans opposite and see if they were preparing to counter-attack or retire, passing the information to divisional Advanced Report Centre.

Division
Training for the northern attack (31 July) began in early June, with emphasis on musketry and attacks on fortified positions. The Guards divisional Signals Company trained 28 men from each brigade as relay runners, additional to the other means of tactical communication. Major-General Fielding held a conference on 10 June to discuss the division's place in the XIV Corps scheme for the attack east and north-east of Boesinghe. Four "bounds" were to be made to the blue, black, green and dotted green lines, by-passing isolated German posts, whch were to be dealt with by reserves. Depending on the state of the German defence, ground was to be taken up to the red line by patrols. Captured German trench lines were to be consolidated and advanced posts established beyond them. Parties were to be detailed for liaison with nerighbouring units and divisions. Six brigades of field artillery were available for the creeping barrage and the division's three machine-gun companies were reinforced by a company from 29th Division for the machine-gun barrage. Times when contact patrol aircraft were to fly overhead observing progress were given. The only light signals allowed were the flares for contact aircraft and the rifle grenade SOS signal.

On 12 June the 2nd Guards Brigade began the march to the front and on 15 June the relief of 38th Division commenced and preparations were begun to cross the Yser canal, which was 23 yd wide, empty and with deep mud in the bed. A divisional conference on 18 June discussed the plans of the 2nd and 3rd Guards Brigades and their liaison arrangements with 38th Division to the right and the French 1st Division on the left. The divisional reserve of 1st Guards Brigade, was to exploit success by forcing a crossing of the Steenbeek and consolidating a bridgehead on the far bank. If the Germans collapsed it was to advance to a line east of Langemarck and Wijdendreft.

The 8th Division moved to Flanders a few days before the Battle of Messines Ridge (7–17 June) and joined XIV Corps in Second Army reserve. On 11 June the division came under II Corps and began to relieve parts of 33rd Division and the 55th Division on the Menin Road at Hooge. Major-General Heneker was able to persuade Gough to cancel a preliminary operation and include it in the main attack. On 12 July the Germans conducted their first mustard gas attack on the divisional rear areas and artillery lines. Two brigades were to advance to the blue line with two battalions each, with the other two to pass through to the black line. Four tanks were attached to each brigade. The 25th Brigade would then attack the green line, assisted by twelve tanks. One battalion with tanks and cavalry would then be ready to advance to the red line, depending on the state of German resistance and 25th Division would be in reserve ready to attack beyond the red line.

After a night raid on 11 July the division was relieved by the 25th Division and began training intensively for trench-to-trench attacks, on ground marked to represent German positions on the objective. A large model was built and a large-scale map produced for officers and men to study and reconnaissances were conducted by officers and staffs to study the ground up to the objective. The divisional artillery was reinforced with the 25th Divisional artillery, three army field brigades, a counter-battery double-group, (one with 6-inch, 8-inch and 12-inch howitzers, the other with 60-pdr and 6-inch guns) a double bombardment group (one group with 6-inch and 8-inch howitzers, the other with 6-inch, 9.2-inch and 15-inch howitzers). Six batteries of 2-inch, three of 6-inch and four of 9.45-inch mortars were added. On 23 July the division returned to the front line and commenced raiding to take prisoners and to watch for a local withdrawal, while tunneling companies prepared large underground chambers to shelter the attacking infantry before the offensive began.

Northern army group
Northern France and Flanders was held by Army Group Crown Prince Rupprecht which by the end of July had 65 divisions. The defence of the Ypres Salient was the responsibility of the German Fourth Army, under the command of General Friedrich Bertram Sixt von Armin. The divisions of the Fourth Army were organised in groups (gruppen) based on the existing corps organisation. Group Lille ran from the southern army boundary to Warneton. Group Wytschaete continued north to Bellewaarde Lake, Group Ypres held the line to the Ypres–Staden railway, Group Dixmude held the ground from north of the railway to Noordschoote and Group Nord held the coast with Marine Corps Flanders.

Behind the ground-holding divisions (Stellungsdivisionen) were a line of Eingreif divisions. The term Ablösungsdivision had been dropped before the French attacks in mid-April to avoid confusion over their purpose, Eingreif meaning interlock, dovetail or intervene being substituted. 207th Division, 12th Division and 119th Division supported Group Wytschaete, 221st Division and 50th Reserve Division supported Group Ypres and 2nd Guard Reserve Division supported Group Dixmude. In addition, the 79th Reserve Division and 3rd Reserve Division were located at Roulers, in Army Group reserve. Group Ghent with the 23rd Division and 9th Reserve divisions were concentrated around Ghent and Bruges and 5th Bavarian Division at Antwerp in case of a British landing in Holland.

The German Fourth Army defended 25 mi of front with three groups; Group Dixmude based on the German XIV Corps headquarters, Group Ypres (III Bavarian Corps) and Group Wytschaete (IX Reserve Corps). Group Staden (Guards Reserve Corps) was added later. Group Dixmude held 12 mi with four front divisions and two Eingreif divisions; Group Ypres held 6 mi, from Pilckem to Menin Road with three front divisions and two Eingreif divisions and Group Wytschaete held a similar length of front south of Menin Road with three front divisions and three Eingreif divisions. The Eingreif divisions were placed behind the Menin and Passchendaele Ridges. 5 mi further back were four more Eingreif divisions and 7 mi beyond them another two in "Group of Northern Armies" reserve.

The Germans were anxious that the British would try to exploit their victory at the Battle of Messines, by advancing to the Tower Hamlets spur beyond the north end of Messines Ridge. On 9 June, Crown Prince Rupprecht proposed a withdrawal to the Flandern Line in the area east of Messines. Construction of defences began but were terminated after Colonel Fritz von Lossberg was appointed the new Chief of Staff of the German Fourth Army. Lossberg rejected the proposed withdrawal to the Flandern Line and ordered that the current front line west of the Oosttaverne Line be held rigidly. The Flandern Stellung in front of the Flandern Line would become the Flandern I Stellung and a new Flandern II Line, forming the back line of a new Flandern II Stellung, would run west of Menin and north to Passchendaele. Construction of another line, Flandern III was started east of Menin north to Moorslede.

Debate among the German commanders continued. On 25 June, First Quartermaster-General Erich Ludendorff suggested to Rupprecht that Group Ypres be withdrawn to the Wilhelm (third) Line, leaving only outposts in the Albrecht (second) Line. On 30 June, Rupprecht's Chief of Staff, General von Kuhl suggested a withdrawal to Flandern I along Passchendaele Ridge, meeting the old front line in the north near Langemarck and Armentières to the south. Such a withdrawal would avoid a hasty retreat from Pilckem Ridge and also force the British into a time-consuming redeployment. Lossberg disagreed, believing that the British would launch a broad front offensive, that the ground east of the Oosttaverne Line was easy to defend, that the Menin Road Ridge could be held and that Pilckem Ridge deprived the British of ground observation over the Steenbeek Valley, while German observation of the area from Passchendaele Ridge allowed the infantry to be supported by observed artillery fire.

Army
The German Fourth Army operation order for the defensive battle was issued on 27 June.The system of defence in depth began with a front system of three breastworks: Ia, Ib and Ic each about 200 yd apart, garrisoned by the four companies of each front battalion, with listening-posts in no-man's-land. About 2000 yd behind these works was the Albrecht ("second" or "artillery protective") Line, the rear boundary of the forward battlezone (Kampffeld). Companies of the support battalions (25% being Sicherheitsbesatzung) to hold the strong-points and 75% being Stosstruppen to counter-attack towards them, were placed at the back of the Kampffeld, half in the pillboxes of the Albrecht Line, to provide a framework for the re-establishment of defence in depth, once the enemy attack had been repulsed. Dispersed in front of the line were divisional Sharpshooter (Scharfschützen) machine-gun nests called the Stutzpunkt-Linie. The Albrecht Line also marked the front of the main battlezone (Grosskampffeld) about 2000 yd deep, with most of the field artillery of the front divisions, behind which was the Wilhelm (third) Line. In pillboxes of the Wilhelm Line were reserve battalions of the front-line regiments in divisional reserve.

From the Wilhelm (third) Line to Flandern I was a rearward battlezone (rückwärtige Kampffeld) containing the support and reserve assembly areas for the Eingreif divisions. The failures at Verdun in December 1916 and at Arras in April 1917 had given more importance to these areas, since the Kampffeld had been overrun during both offensives and the garrisons lost. It was anticipated that the main defensive engagement would take place in the Grosskampffeld by the reserve regiments and Eingreif divisions, against attackers who had been slowed and depleted by the forward garrisons before these were destroyed. "... they will have done their duty so long as they compel the enemy to use up his supports, delay his entry into the position, and disorganise his waves of attack." (General Balcke).

The leading regiment of an Eingreif (interlocking) division was to advance into the zone of the front division with its other two regiments moving forward in close support. Eingreif divisions were accommodated 10000 - 12000 yd behind the front line and began their advance to their assembly areas in the rückwärtige Kampffeld, ready to intervene in the Grosskampffeld, for den sofortigen Gegenstoss (the instant-immediate counterthrust). Lossberg rejected elastic defence in Flanders, there was little prospect of operational pauses between British attacks towards Flandern I, since the British had such a mass of artillery and the infrastructure necessary to supply it with huge amounts of ammunition, much of which had been built in the period between the attack at Messines and 31 July. Lossberg ordered that the front line be fought for at all costs and immediate counter-attacks be delivered to recapture any lost sector. Lossberg reiterated his belief that a trench garrison which retired in a zone of fire quickly became disorganised and could not counter-attack, losing the sector and creating difficulties for troops on the flanks.

Counter-attack was to be the main defensive tactic, since local withdrawals would only disorganise the troops moving forward to their assistance. Front line troops were not expected to cling to shelters, which were man traps but leave them as soon as the battle began, moving forward and to the flanks to avoid enemy fire and to counter-attack. German infantry equipment had recently been improved by the arrival of 36 MG08/15 (equivalent to the British Lewis Gun) per regiment. The Trupp of eight men was augmented by a MG08/15 crew of four men to become a Gruppe, with the Trupp becoming a Stosstrupp. The extra firepower gave the German unit better means for fire and manoeuvre. 60% of the front line garrison were Stosstrupps and 40% were Stossgruppen, based in the forward battlezone. 80% of the Stoss-kompagnien occupied the Albrecht (second) Line and Stoss-batallione in divisional reserve (all being Stoss formations) and then the Eingreif division (all Stoss formations) was based in the Fredericus Rex and Triarii positions. The essence of all of these defensive preparations was riposte, in accordance with Clausewitz's view that defence foreshadows attack.

Army
British Expeditionary Force (BEF) General Headquarters quickly studied the results of the attack of 31 July and on 7 August sent questions to the army headquarters on how to attack in the new conditions produced by German defence-in-depth based on strong points, pillboxes and rapid counter-attacks by local reserves and Eingreif divisions. Plumer replied on 12 August, placing more emphasis on mopping up captured ground, making local reserves available to deal with hasty local German counter-attacks and having larger numbers of reserves available to crush German organised counter-attacks. After a conference with the Corps commanders on 27 August, Plumer issued "Notes on Training and Preparation for Offensive Operations" on 31 August, which expanded on his reply to General Headquarters, describing the need for attacks with more depth and more scope for local initiative, enabled by unit commanders down to the infantry company, keeping a reserve ready to meet German counter-attacks. Communication was stressed but the standardization achieved since 1916 allowed this to be reduced to a reference to SS 148.

Plumer issued a "Preliminary Operations Order" on 1 September, defining an area of operations from Broodseinde southwards. Four corps with fourteen divisions were to be involved in the attack. Five of the thirteen Fifth Army divisions extended the attack northwards to the Ypres–Staden railway. The process of arranging the attack involved the divisions soon afterwards. New infantry formations were introduced by both armies to counter the German irregular pillbox defence and the impossibility of maintaining line formations on ground full of flooded shell-craters. Waves of infantry were replaced by a thin line of skirmishers leading small columns. The XVIII Corps commander Ivor Maxse called this one of the "distinguishing features" of the attack, along with the revival of the use of the rifle as the primary infantry weapon, the addition of Stokes mortars to creeping barrages and "draw net" barrages, where field guns began a barrage 1500 yd behind the German front line then crept towards it, which were fired several times before the attack began. The pattern of organisation established before the Battle of Menin Road Ridge became the standard method of the Second Army.

The plan relied on the use of more medium and heavy artillery, which was brought into the area of the Gheluvelt Plateau from VIII Corps on the right of the Second Army and by removing more guns from the Third and Fourth armies further south. The heavy artillery reinforcements were to be used destroy German strongpoints, pillboxes and machine gun nests, which were more numerous beyond the German outpost zones which had already been captured and to engage in more counter-battery fire. 575 heavy and medium and 720 field guns and howitzers were allocated to Plumer for the battle, an equivalent of one artillery piece for every 5 yd of the attack front, more than double the proportion in the battle of Pilckem Ridge. The ammunition requirements for the seven day's bombardment before to the assault was estimated at 3.5 million rounds. which created a density of fire four times greater than for the attack of 31 July. Heavy and medium howitzers were to make two layers of the creeping barrage, each 200 yd deep, ahead of two field artillery belts equally deep, plus a machine-gun barrage in the middle. Beyond the "creeper", four heavy artillery counter-battery double groups, with 222 guns and howitzers covered a 7000 yd front, ready to engage with gas and high-explosive shell any German guns which opened fire.

Corps
The three-week operational pause in September, originated from Lieutenant-Generals Morland and Birdwood the X Corps and I Anzac Corps commanders at the conference of 27 August. The attacking corps made their plans within the framework of the Second Army plan using "General Principles on Which the Artillery Plan Will be Drawn" of 29 August, which described the multi-layer creeping barrage and the use of fuze 106 to avoid adding more craters to the ground. Decisions over practice barrages and machine-gun barrages were left to the corps commanders. The Second Army and both corps did visibility tests, to decide when zero hour should be set and discussed the use of wireless and gun-carrying tanks with Plumer on 15 September. X Corps issued its first "Instruction" on 1 September, giving times and boundaries to its divisions, with details to follow.

More details came from X Corps in a new "Instruction" on 7 September, giving the green line as the final objective for the attack and the black line for the next attack (intended for roughly six days hence), reduced the depth of the barrage from 2000 - 1000 yd and added a machine-gun barrage, to be fired by the attacking divisions and coordinated by the Corps Machine-Gun Officer and the Second Army artillery commander. Artillery details covered eight pages and signalling another seven. A Corps Intelligence balloon was arranged to receive light signals and messenger pigeons were issued to corps observers, reporting to a Corps Advanced Intelligence Report Centre so that information could be collected and circulated swiftly. Delegation forward was demonstrated by the next "Instructions" on 10 September, which gave a framework for the creeping barrage fired by the divisional artillery, the details being left to the divisions, as was harassing fire on German positions. Double bombardment groups (first used by X Corps at Messines) were affiliated with divisional headquarters. The X Corps report on the attack of 20 September, stated that success was due to the artillery and machine-gun barrages, the ease of moving troops over rebuilt roads and tracks behind the front and the much better co-operation of infantry, artillery and Royal Flying Corps.

Division
On 7 September the 1st Australian Division commander, announced the attack to his staff and next day the ground was studied. "Divisional Order 31" was issued on 9 September, giving the intent of the operation and listed neighbouring formations, the placement of the division's brigades and the deployment of the two attacking brigades on a front of one battalion, with a battalion advancing to the first objective, one moving through it to the second objective and two more to the final objective, 1500 yd beyond the original front line. A map was appended to the Order showing the red, blue and green lines to be captured. The creeping barrage by the division's five field artillery brigades and bombardments from artillery under corps and army command was described. Special attention was given to mopping up procedures and the detailing of particular units to capture selected German strong points.

On 11 September "Divisional Order 32" detailed the march to the division's assembly area near Ypres and on 14 September "Instruction No. 2" of Order 31, added details of the artillery plan and laid down routes for the approach march. More reconnaissances of the front line were made on 15 September and signallers began to bury cables six feet deep. "Instruction No. 3" detailed the strong points to be built to accommodate a platoon each on captured ground, equipment and clothing to conform to Section 31 of SS 135, with an amendment that the battalions on the final objective would carry more ammunition. Coloured patches corresponding to the objective lines were to be worn on helmets and the 1st Australian Infantry Brigade was to be held back, ready to reinforce the attacking brigades or to defeat German counter-attacks. Compasses were issued to officers and white tape was to be used to mark approach routes, jumping-off points and unit boundaries, to help the infantry keep direction. Troops attacking the first objective were ordered not to fix bayonets until the barrage commenced, to increase the possibility of surprise.

"Instruction No. 4" comprised intelligence instructions for the questioning of prisoners and the gleaning and dissemination of useful information. Men identified by arm-bands, were to scour the battlefield for German documents, using maps of German headquarters, signals offices and dug-outs, the information to be sent to a divisional collecting point. "Instruction No. 5" was devoted to liaison, with officers attached to brigades, to report to the divisional commander. Brigades liaised with the other Australian brigades and those of neighbouring divisions, battalions liaising in the same manner. Artillery liaison officers were appointed down to infantry brigades and battalion and company officers were told to keep close to artillery Forward Observation Officers. "Instruction no. 6" covered engineer and pioneer work for the building of strong points, at the places determined in "Divisional Order 31". An Engineer Field Company was attached to each brigade and the Pioneer Battalion was made responsible for the maintenance and extension of communications, including tramways, mule and duckboard tracks and communication trenches. Two supply routes were defined and next day engineer officers were added to the liaison system within brigade headquarters.

Communication within the division was addressed by "Instruction No. 7" on 16 September, which discussed telegraph, telephones and cable burying; visual communication via six reporting stations; wireless and power buzzers. Motor-cycle despatch riders were linked to runners established forward of brigade headquarters, with five posts for runners marked, pairs of runners no more than 50 yd apart and messenger pigeons issued to brigades and artillery observers. Separate lines were laid for artillery use and aircraft liaison followed SS 148, with infantry battalions provided with panels to signal from the ground. "Instruction No. 8" covered medical arrangements from Regimental Aid Posts, (with a medical officer and four squads of stretcher bearers each) back to Casualty Clearing Stations along marked evacuation routes. "Instruction No. 9" laid down the use of machine-guns in the attack; 72 machine-guns were to be part of the creeping barrage, from machine-gun companies attached to each brigade. The Divisional Machine-Gun Officer was to keep close touch with brigade headquarters, to be ready to act on SOS calls from the infantry. "Instruction No. 10" was a "Summary of Arrangements for Co-operation between Infantry and Artillery on Forthcoming Operations" and detailed artillery liaison down to battalion. A brigade of field artillery (three batteries of 18-pdr field guns, one of 4.5-inch howitzers) was added to the barrage and made available to artillery liaison officers at brigades as needed. Divisional headquarters had two 6-inch howitzer batteries with eight guns for the same purpose.

"Instruction No. 12" on 17 September, covered equipment to be carried into action, the attachment of a troop of Light Horse to Major-General H. B. Walker, the Divisional commander, to carry orders and restrictions on the use of telephones in the front line, to hamper German eavesdropping. Instructions 13–15, between 18 September and the start of the attack, covered late changes, such as reserving the use of telephones to unit commanders and the provision of two wireless tanks for the south-east corner of Glencorse Wood, for local use and as an emergency station for both Australian divisions.

To the right of 1st Australian Division was the 23rd Division, which followed the same pattern of planning and organisation. The warning order was issued on 3 September and the divisional plan issued on 6 September. Appendices followed from 9–15 September with some amendments on 17 September. On 8 September X Corps instructed that divisional commanders for the attack, were to take over their fronts on 13 September, before the divisions there were relieved by the attacking divisions and that brigade headquarters were to be taken over on 16 September. Intelligence gathering continued up to the attack and was used to amend plans. When aerial photographs showed that ground around Dumbarton Lakes, to the south of Inverness Copse was far muddier than expected, the plan was changed so that the infantry battalions sidestepped the marsh.

On 11 September the 23rd Division commander Major-General J. M. Babington, pointed out to the X Corps commander Lieutenant-General Morland, that he was leaving the arrangements to deal with German counter-attacks to his brigade commanders but felt that the area suggested by corps was on a forward slope and wanted to put the reserve behind the blue (second) line. Morland reiterated his intent to ensure that the counter-attack reserve was ready to intervene while German troops were reorganising, though the means to achieve this were left to Babington's discretion and that the 23rd Division reserve brigade, would conduct any prepared counter-attacks. A "Final Order" was issued on 17 September, as a summary and added information about the Bavarian Ersatz Division opposite and possible German counter-attack routes. It stressed that observation was needed over the Reutelbeek and Kronnebeek valleys, when the final objective was consolidated and that Situation Reports be sent when brigades reached their objectives and at two-hourly intervals afterwards. Both divisions reached all their objectives on 20 September and wrote up the experience afterwards, the 23rd Division "Comment on Operations" being published as a Second Army document. The pattern for subsequent British attacks was established and Second Army orders and artillery instructions became increasingly formulaic. Orders usually began with "Ref. 'Attack Map'" and the stages of the attack were described in relation to it. Orders were terse statements of the timetable, which corps were involved, any corps movements and when the attack should take place.

German defensive changes: late 1917
22 September: after the defeat of Menin Road the German defensive deployment was changed. In August German front-line divisions had two regiments of three battalions forward, with the third regiment in reserve. The front battalions had needed to be relieved much more frequently than expected, due to constant British bombardments between attacks and the weather, which had caused units to become mixed up. Reserve regiments had not been able to intervene quickly, leaving front battalions unsupported until Eingreif divisions arrived, some hours after the commencement of the attack. The deployment was changed to increase the number of troops in the front zone. By 26 September all three regiments of the front-line division were forward, each holding an area 1000 yd wide and 3000 yd deep; one battalion was placed in the front-line, the second in support and the third in close reserve.

The battalions were to move forward successively, to engage fresh enemy battalions, which had leap-frogged through those that had delivered the first attack. The Eingreif divisions were to deliver an organised attack with artillery support, later in the day before the British could consolidate their new line. The change was intended to remedy the neutralization of the front division's reserve, achieved by the British artillery on 20 September, so that it could intervene before the Eingreif divisions arrived. On 22 September new tactical requirements were laid down: more artillery counter-bombardment was to be used between British attacks, half against British artillery and half against infantry, increased raiding was ordered to induce the British to hold their positions in greater strength, giving German artillery a denser target; better artillery observation was demanded in the battle zone, to increase the accuracy of German artillery fire when British troops advanced into it and quicker counter-attacks were to be made.

30 September: after the costly defeats of Menin Road on 20 September and Polygon Wood on 26 September, the German commanders made more changes to the defensive deployment of their troops and altered their counter-attack tactics, which had been negated by Plumer's combination of limited attack and much greater artillery fire-power, than that available to the Fifth Army in August. German Eingreif divisions had engaged in "an advance to contact during mobile operations" in August, which had given the Germans several costly defensive successes. German counter-attacks in September had been "assaults on reinforced field positions", due to the short British infantry advances and emphasis on defeating German Gegenstoss ("instant-immediate") counter-attacks. The period of dry weather and clear skies which began in early September had greatly increased the effectiveness of British air observation and artillery fire. German counter-attacks were defeated with heavy casualties, after arriving too late to take advantage of the attackers' disorganisation. The British changes meant that a defence in depth had been established, much of it on reverse slopes, behind standing barrages, in dry clear weather, with specialist air reconnaissance for observation of German troop movements and improved contact patrolling and ground-attack operations by the Royal Flying Corps. Such German artillery which was able to fire despite British counter-battery shelling, became unsystematic due to uncertainty over the whereabouts of German infantry and British infantry benefitted from the opposite. On 28 September Albrecht von Thaer, Staff Officer at Group Wytschaete wrote that the experience was "awful" and that he did not know what to do.

Ludendorff later wrote that he had regularly discussed the situation with General von Kuhl and Colonel von Lossberg, to try to find a remedy for the overwhelming British attacks. Ludendorff ordered a strengthening of the forward garrisons by the ground holding divisions, all available machine guns, including those of the support and reserve battalions of the front line regiments, were sent into the forward zone to form a cordon of four to eight guns every 250 yd. The Stoss regiment of each Eingreif division, was placed behind each front division, in the artillery protective line behind the forward battle zone (which increased the ratio of Eingreif divisions to Stellungsdivisionen to 1:1). The Stoss regiment was to be available to launch counter-attacks while the British were consolidating; the remainder of each Eingreif division was to be withheld for a Gegenangriff (methodical counter-attack) on the next day or the one after. Between British attacks, the Eingreif divisions were to make more spoiling attacks.

A Fourth Army operation order of 30 September, pointed out that the German position in Flanders was restricted by the local topography, the proximity of the coast and the Dutch frontier, which made local withdrawals impossible. The instructions of 22 September were to be followed, with more bombardment by field artillery, using at least half of the heavy artillery's ammunition for observed fire on infantry positions in captured pill-boxes, command posts, machine-gun nests, duckboard tracks and field railways. Gas bombardment was to be increased on forward positions and artillery emplacements, whenever the winds allowed. Every effort was to be made to induce the British to reinforce their forward positions, where the German artillery could engage them, by making spoiling attacks to recapture pillboxes, improve defensive positions and harass the British infantry with patrols and diversionary bombardments. Between 26 September and 3 October the Germans attacked and counter-attacked at least 24 times. British intelligence predicted the German changes in an intelligence summary of 1 October, foreseeing the big German counterattack planned for 4 October.

7–13 October: on 7 October the Fourth Army abandoned the reinforcement of the front defence zone after the "black day" of 4 October. Front line regiments were dispersed again, with reserve battalions moved back behind the artillery protective line and Eingreif divisions organised to intervene as swiftly as possible, despite the risk of being devastated by the British artillery. Counter-battery fire against British artillery was to be increased to protect the Eingreif divisions as they advanced. Ludendorff insisted on an advanced zone, (Vorfeld) 500 - 1000 yd deep, to be occupied by a thin line of sentries with a few machine-guns. The sentries were to retire on the main line of resistance (Hauptwiederstandslinie) at the back of this advanced zone when attacked, while the artillery was quickly to barrage the area in front of it. Support and reserve battalions of the front-line and Eingreif divisions, would gain time to move up to the main line of resistance where the battle would be fought, if the artillery-fire had not stopped the British infantry advance. An Eingreif division was to be placed behind each front-line division, with instructions to ensure that it reached the British before they could consolidate. If a swift counter-attack was not possible, there was to be a delay to organised a methodical counter-attack, after ample artillery preparation.

The revised defensive scheme was promulgated on 13 October, over Rupprecht's objections. Artillery-fire was to replace the machine-gun defence of the forward zone as far as possible, which Rupprecht believed would allow the British artillery too much freedom to operate. The thin line of sentries of one or two Gruppen (thirteen men and a light machine-gun each) in company sectors proved inadequate, as the British were easily able to attack them and lift prisoners. At the end of October the sentry line was replaced by a conventional outpost system of double Gruppen. By this stage of the campaign the German defence was based on two divisions holding a front 2500 yd wide and 8000 yd deep, half the area that two divisions previously were expected to hold. The necessity of such reinforcement was caused by the weather, devastating British artillery fire and the decline in the numbers and quality of German infantry. Concealment to create an invisible garrison (die Leere des Gefechtsfeldes) was emphasised, to protect the divisions from British firepower, by avoiding anything resembling a trench system, in favour of dispersal in crater fields. Such a method was only made feasible by the rapid rotation of units and battalions of the front-divisions were relieved after two days and divisions every six days.

Army
The Battle of Cambrai originated on 23 August 1917 with a proposal from Brigadier-General H. D. Du Pree (IV Corps, Third Army) for a surprise attack with tank support near Flesquières, to exploit the lack of German artillery in the area and the relatively good going for tanks. Headquarters (HQ) of the Third Army (commanded by General Byng) and Brigadier-General H.H. Tudor, Commander Royal Artillery (CRA) 9th Division did much to expand the proposal, which was then planned in the systematic manner of the British offensives earlier in the year, founded on the S.S. manuals derived from analysis of the Battle of the Somme and French experience. Draft schemes were issued to Corps, containing the objectives and the achievement of surprise, by dispensing with a preliminary bombardment. Infantry were to advance behind a mass of tanks to the first two objective lines (blue and brown) by leapfrogging, to penetrate the Hindenburg line. An advance to the red line and beyond was to be udertaken by cavalry, a novel feature intended to be made possible by the surprise and swift initial advance, with the details of the advance to be decided by the Corps. The third part of the plan required the cavalry to envelop Cambrai, followed up by infantry, beginning in the south with III Corps then successively to the north by IV, VI and XVII Corps. If it occurred, the cavalry advance would be about 10 mi deep, two more than that planned for the Arras offensive earlier in the year.

"Scheme GY (25 October 1917) was arranged by Army conferences where the objectives were given by Byng then the means to achieve them were decided by the Corps commanders. Third Army Headquarters then issued memoranda drawing attention to certain aspects of the plan. "Third Army Instructions To Cavalry Corps" were sent by Byng to its commander Lt.-Gen. C.T. McM. Kavanagh on 13 November, covering liaison with tanks and infantry and describing the role of the cavalry in advancing about 4 ½ hours after zero hour, through the infantry at Masnières and Marcoing to surround Cambrai. On 14 November 1917, III Corps was told when to move its reserve, the 29th Division forward, to capture the canal crossings at Masnières and Marcoing. The Royal Flying Corps, Tank Corps and Royal Artillery arranged their plans through Third Army Headquarters, rather than direct with corps headquarters, to ensure that the new artillery techniques, the role of the tanks in creating gaps in the German wire ahead of the infantry and the increasingly-important organised air operations over the battlefield were co-ordinated.

Artillery planning for the attack saw the greatest change in technique, which was intended to exploit the tactical potential of silent registration. The artillery plan for the first part of the attack was decided by Third Army headquarters, with no discretion being allowed to Corps to make changes, until German resistance after the commencement of the operation required Corps to resume tactical control. The use of silent registration and the need for secrecy and uniformity of practice, led to Third Army headquarters issuing detailed instructions (Third Army Artillery Instructions, 18–20) governing the use of artillery before the offensive and the combination of suppressive, rather than destructive artillery-fire with tank action, to clear the way for the infantry advance and cavalry exploitation.

Corps
Corps planning for the Cambrai operation followed the routine system established since early 1917. IV Corps (Lieutenant-General Sir C. L. Woolcombe) issued its draft plan on 31 October, giving the concept of the plan, the three stages and the troops allotted, with the measures needed to prepare the area and plan the assembly of troops. The administrative, intelligence and signalling instructions necessary for this were issued by the respective corps staff branches. During planning, IV Corps issued more instructions regarding the role of its divisions, particularly for the period after the Hindenburg Support system was captured and made the decisions that the Tank Corps was to use all its tanks on the first day and that the troops involved in the attack would move to the front immediately before the attack, rather than a few days previous to be fresh, to prevent the Germans making deductions from prisoners and to give the infantry more time for training with tanks, responsibility for this being delegated to infantry division commanders and the tank brigade attached to IV Corps. Further instructions were issued from 10–17 November on concentration and assembly, secrecy, preliminary movements, communication of orders, codes and ciphers, signals, later stages of the attack and cavalry liaison..

The Tank Corps also followed this routine, sending recommendations to the Third Army headquarters for approval, on the distribution of its units and the combined training of the tanks and the infantry with which they were attached, based on the "Notes" issued on 4 October, which summarized experience gained by the Tank Corps since April 1917 and amendments issued on 10 November. Third Army headquarters issued two "Notes" on 30 October, covering tank-infantry training and operations. In "Tank and Infantry Operations Without Methodical Artillery Preparation" of 30 October 1917, each corps was told to keep the instructions secret to ensure surprise, that tank sections should attack specific areas, that objectives should be reserved for an echelon of tanks each, that an advanced tank should keep German heads down, while the main body and infantry crossed German trenches, that the main body of tanks should stay on the British side of the German line being attacked, that tanks would be allotted according to the number of German positions in the area and work in threes to cover 100 - 200 yd of front. Only a platoon of infantry should work with each tank, to avoid bunching when moving through lanes crushed by the tanks in the German barbed wire and that the infantry should move in section files. Further sections described the care needed when tanks crossed barbed wire, so that following tanks would not pull up wire flattened by the leading tanks, the use and marking of trenches filled by fascines and the principles of tank–infantry co-operation.

In "Notes on Infantry and Tank Operations" also of 30 October, Third Army HQ described the characteristics of the tanks and the tank Corps organisation, how to identify individual tanks, the frontage per tank, formations, assembly, concealment, the method of moving forward to the attack, tank objectives, infantry co-operation, portage of ammunition, wire and trench crossing, signalling, counter-battery work, staff liaison and reporting and stated that success depended on the mechanical fitness of the tanks, efficient assembly on the battlefield, obvious and easily-seen objectives, prepared and concealed approaches and thorough briefing of all tank and infantry officers. Third Army HQ delegated operational control of the tanks to III and IV Corps, which allocated tanks to their divisions then required division commanders to arrange training with the attached tanks. For liaison, each corps sent a staff officer to the tank brigade headquarters attached.

The Royal Flying Corps continued its development of ground attack operations, with a more systematic organisation of duties and coverage of the battlefield, drawing on the lessons of the Third Battle of Ypres and the pioneering work done during the capture of Hill 70 in August. The smaller area of operations at Cambrai and the growth of the RFC meant that more aircraft could be allotted to each task, than had been the case at times in Flanders. The most notable difference in the air plan for the battle was in artillery co-operation, since air activity over the Cambrai area before the offensive was restricted (along with the quantity of artillery and ammunition expenditure) to the usual amount to maintain secrecy, leaving no time before the battle for observation of artillery fire. The positions of active German artillery batteries was to be observed once the battle began and prompt corrections to the artillery given, for counter-battery neutralisation and for destructive fire against groups of German infantry. Four squadrons of fighters were reserved for ground attacks against artillery, machine-gun nests and troops according to a plan using lists of the most dangerous German artillery positions. The ground attack squadrons were given three groups of ground targets to be patrolled all day and a forward aerodrome was established at Bapaume to allow aircraft to resume patrols and attacks quickly.

Division
The 51st Division moved from the Ypres front in early October and received a surprise when warned of another operation, having already had 10,523 casualties in 1917. To inflict a similar surprise on the Germans, the division stayed at Hermaville and a replica of the German defenses to be attacked, was laid out to the west of Arras. To mislead the Germans, the division did not occupy the front line trenches before the attack and observation parties visited the trenches wearing trousers rather than kilts. To concentrate the division in the battle area only 36–48 hours beforehand, the Commander Royal Engineers (CRE) with three companies of engineers and an infantry battalion began to prepare hidden shelters in the IV Corps area in early November, providing camouflaged accommodation for 5,500 men at Metz and for 4,000 men in Havrincourt Wood by 19 November. Supply dumps, infantry and artillery tracks, dressing stations and water points for 7,000 horses per hour were built, with no increase in movement of lorries by day and no work in forward areas allowed.

Training was conducted on the replica, with the tanks due to operate with the division. The 1st Brigade of the Tank Corps with 72 tanks, supplied a battalion to each of the two attacking infantry brigades. Twelve "Rovers" were to move forward at zero, to crush barbed wire and engage any machine-gun nests found between the German trench lines. 150 yd behind the Rovers, a second wave of 36 "Fighting" tanks were to deal with the Germans in trenches up to the blue line. All remaining tanks were to form a third wave and reinforce the first two waves for the attack on Flesquières Ridge. Three tanks were allotted to each platoon front of about 150 yd, so that two tanks could attack the Germans in the trench to their front as the centre tank advanced to the trench beyond. The first two tanks were to follow up as soon as their infantry reached the first trench.

Due to the number of German communication trenches, sap heads, crater posts, detached posts and subsidiary trenches in the area, the second wave tanks were given specific German positions, routes and positions in villages to deal with, as well as attacking the main Hindenburg trenches. Infantry were to follow 150 - 200 yd behind, to attack trenches as soon as they were engaged by the tanks and mark gaps in the wire; each tank carried spare ammunition for the infantry. Training in the 51st Division and 62nd Division departed from the "Notes" issued by the Tank Corps through Third Army HQ, by having infantry keep a greater distance from the tanks and to move in lines rather than files, along with the use of Rovers ahead of the Fighting Tanks.

Northern army group
Rupprecht and his Chief of Staff, Von Kuhl were still anxious about the situation in Flanders on the Fourth Army front in November, having lost Passchendaele village and more of from 6–10 November. That the British offensive at Ypres had ended was considered possible but there was no anticipation of an attack elsewhere, so planning had begun for operations in 1918. In his appreciation of 17 November, Rupprecht concluded that large attacks were improbable and that small attacks on the areas of the Sixth and Second armies were possible, if the British had ended their operations in Flanders [which they had after the success of 10 November]. The attack at Cambrai came "as a complete surprise" and Ludendorff criticised the Army Group for being too distracted by the Flanders front. The Army Group and the Supreme Army Command (OHL) could only react to the British attack on 20 November by issuing orders for reinforcements to rush to the Second Army, although Rupprecht pointed out that the system of rapid relief of divisions in Flanders, would break down if many divisions were removed and that the rail network was overloaded so that rapid reinforcement of the Cambrai front was not guaranteed. Ludendorff responded by taking additional divisions from Army Group "German Crown Prince" in the central section of the western front. The next day Rupprecht ordered all of the truck-mounted anti-aircraft guns in the Fourth and Sixth armies to the Second Army for use as anti-tank guns.

On 27 November, Ludendorff, Rupprecht and the Chiefs of Staff of Army Group "German Crown Prince" and the 7th Army met at the Second Army headquarters in Le Cateau. Delays in transporting reinforcements and artillery ammunition reported by Von der Marwitz, led Ludendorff to accept a delay of an intended counter-offensive until 30 November. It was at this meeting that a more ambitious aim of cutting off the British troops in the Bourlon salient and rolling up the British line northwards, replaced the original plan to push the British back behind the Siegfried I Stellung defences, when Rupprecht was able to offer two more divisions from Flanders. On 27 November Rupprecht issued orders to the Second Army for the counter-offensive. The main effort was to be made by Groups Caudry and Busigny, attacking west towards the village of Metz, capturing Flesquières and Havrincourt Wood from the south. Group Arras was to attack southwards west of Bourlon Wood, after the main attack had begun. Fresh divisions from Rupprecht's army group and OHL Reserve were to be ready to exploit success. Rupprecht wrote that the recovery of the Siegfried I Stellung positions was necessary. A subsidiary attack was to be prepared by the Second Army north of St. Quentin, for exploitation if a great success was achieved.

Army
Under the command of General of Cavalry Georg von der Marwitz, the Second Army held the western front from just south of Arras to the Oise north of Barisis. Many of the Second Army divisions had been exchanged for ones exhausted by the fighting in Flanders. In a report sent to the Army Group headquarters on 17 November, the Second Army estimated that it would be another fortnight before 54th Division and 183rd Division would be battleworthy, 9th Reserve Division was only capable of holding a quiet front and 20th Landwehr Division had been so damaged at Ypres, that it was to be sent to the eastern front as soon the 107th Division from Russia arrived. In Group Caudry the loyalty of 107th Division's 350 troops from Alsace-Lorraine was questioned and its lack of equipment meant that the division could not be assessed. None of the divisions in Group Arras were considered battleworthy after their time in Flanders.

As soon as the crisis at Cambrai broke on 20 November, reserves were rushed to the area; an average of 160 trains per day arriving at Cambrai. The delivery of reinforcements and ammunition was not sufficient to allow the early counter-attack originally hoped for and Rupprecht and Von Kuhl imposed 30 November as the date for the counter-offensive, after several delays requested by the Second Army staff. The possibility of a much more ambitious counter-offensive than originally envisaged, discussed at the meeting on 27 November by Ludendorff, Rupprecht and Marwitz with their staffs, required Group Arras to participate despite the tiredness of its divisions, which had been made worse by the delay in preparing the counter-offensive. Metz en Couture and the higher ground around Flesquières were 10 kn behind the British front line and Marwitz's doubts about the divisions in Group Arras, despite the need for them to participate in the bigger operation, led to a compromise. An experimental deployment for the attack behind a smokescreen and a delay of the advance until after the attack by Groups Caudry and Busigny had made itself felt were chosen.

Gruppe/corps
In November Group Arras had been transferred from the Sixth Army further north, holding the area from Inchy to the Arras–Cambrai road near Guémappe. Group Caudry held the area south of Guémappe to Bellicourt, beyond which was Group St. Quentin. Confident in the strength of the Siegfriedstellung (Hindenburg Line) and that a big attack would be preceded by a long bombardment, giving the Germans time to move forces to the area, "Absolutely everything which could be stripped out of the Cambrai front was taken to Flanders", (Adjutant, 108 Brigade, 9th Reserve Division) to reinforce the Schwerpunkt (point of main effort) in Flanders. The unconventional British attack on 20 November obtained strategic, operational and a measure of tactical surprise, inflicting heavy losses and taking ground quickly.

By 23 November reinforcements reaching the Second Army, allowed the creation of two groups based on the XXIII Reserve Corps (Group Busigny) to the south of Group Caudry, opposite the British VII Corps and Group Lewarde (XVIII Corps) taking over the right hand divisions of Group Arras. Eighteen divisions were massed on the Cambrai front, in time for the 30 November counter-offensive. Ten divisions were considered battleworthy, although most of the divisions in Group Arras had been exhausted, by the defensive battles around Bourlon Wood. 79th Reserve Division was in Second Army reserve and eight more divisions were available in Army Group and OHL reserve.

In the rush to prepare the counter-attack originally planned, then the bigger counter-offensive of 30 November, after the success of the defensive battles around Bourlon Wood and rapid reinforcement of the Cambrai front, (in one area, 33 artillery batteries were emplaced in seven days and 60 minenwerfer batteries in three days) the three attacking Groups and their divisions had to amend their plans twice before the attack could commence. Götterdämmerung, Group Caudry's plan eventually became Götterdämmerung 3 as more divisions were added to the attack and Group and divisional boundaries adapted to their arrival. Group Busigny reported that transport difficulties had made it impossible to distribute sufficient ammunition to its divisions. In Group Caudry some of the artillery and mortars arrived too late to be well placed, the attacking infantry lacked time to study the plan and rehearse and some flamethowers had no fuel until the last minute.

Division
During the fighting at Ypres, exhausted German divisions had been moved into the Second Army area to rest and absorb replacements; the 54th Division had arrived at the end of August, severely depleted by the Battle of Langemarck and took over responsibility for 6 mi of trench line, supported by 34 captured field artillery pieces, with 1,000–1,500 rounds per battery and a reserve of only 4,600 shells. The division found that their new positions were overlooked by the British front line, 600 - 700 yd away from German the outposts, behind which were lines K1–K3 and then an intermediate position (Zwischenstellung). The outpost line was manned at night and the strogpoints (Widerstandnester) permanently. The division improved its positions by building elaborate barbed wire obstacles and dug more trenches and dugouts, despite the frequency with which British artillery destroyed them. Vigorous patrolling and prisoner snatches challenged British dominance of no-man's-land. Previous to its dispatch to Flanders, the 54th Division had engaged French tanks during the Nivelle Offensive and afterwards had more anti-tank training. The 9th Reserve Division moved to the Cambrai front from Flanders at the end of September, depleted by heavy losses in the fighting around Zandvoorde and adopted the same raiding policy of the 54th Division, which led to the discovery in no-man's-land of a dead British Tank Corps soldier on 28 October. The news was passed on to intelligence staffs who discounted it. Demand for ammunition in Flanders was so great that larger more revealing raids on the Cambrai front were not possible.

By 29 November the German Second Army had eighteen divisions on the Cambrai front. After the desperate defensive fighting of 20–27 November the divisions had to prepare hurriedly for the counter-offensive eventually begun on 30 November, the first offensive against the British since the Second Battle of Ypres in April 1915. Similar methods to those used by the British to obtain surprise were used, artillery ranging was minimal, a one-hour bombardment before the attack was planned, with a rolling bombardment moving at a rate of 100 m in five minutes to precede the infantry, while the British in Bourlon Wood were to be neutralised by a gas and high-explosive bombardment. Built-up areas were to be bombarded by howitzers and by-passed by the foremost infantry and then attacked from all sides by following troops. Troops moving beyond by-passed British positions (which were mostly captured German positions of the Siegfriedstellung) were to overcome centres of resistance by infiltration and envelopment, with minenwerfer, light and field artillery acoompanying the infantry for the first time, each battery having a platoon of pioneers and a light machine-gun crew; communication was to be assisted by the use of colour-coded light signals. Poor weather and lack of time inhibited training but some rehearsals were possible, using Stosstrupp personnel as instructors; the 34th Division managed to rehearse infiltration tactics on 28 November.

German air units were concentrated in the area but poor weather hampered air reconnaissance by both sides. Some German divisions had been so depleted in the earlier fighting, that their role was minimised. In Group Caudry, 107th Division was ordered to conform to the advances of its neighbouring divisions and occupy higher ground near Marcoing. The 9th Reserve Division was only to advance to the Trescault heights, after the 28th Division and 220th Division had made the initial break-in. In Group Arras, the 214th Division was left out of the attack and other tired divisions given limited tasks.

Conclusion
The new German area defence system failed badly at Verdun 15 December 1916 and again at Arras 9 April 1917, when troops had been kept in obsolete defences and by the belated commitment of the counter-attacking divisions, which were held too far back, against Allied attacking methods and equipment which were much improved from 1916. The new system was made to work in time for the Nivelle Offensive in April. Reinforcements and changes brought about in the German Sixth Army by Colonel von Lossberg, after the débaĉle of 9 April, served to contain British attacks for the remainder of the Battles of Arras, inflicting heavy infantry losses on the British. The calamitous losses endured by the seven German front-holding divisions on 9 April were not repeated, although the defensive operations in later April and May were still costly in infantry. Most of the ground behind the new front position chosen by Von Lossberg and made ready by 13 April was held for the remainder of the battle.

Many writers have called the Third Battle of Ypres a British empire failure. Others say it was not a military failure but a Pyrrhic victory. Research over the last 25 years suggests that all the British and German commanders thought carefully about what they were doing, learned quickly and had efficient forces capable of quick changes of method. The capture of Passchendaele Ridge was extremely difficult, due in no small part to the skill and determination of the German army and the huge problem of waging war without great advantages in technology or tactics. The course of the battles of Arras and the French battles of the Nivelle Offensive earlier in the year suggest that a campaign of this nature was unavoidable. Smaller limited operations like Messines Ridge, Hill 70, the Second Offensive Battle of Verdun and Malmaison were strikingly successful but were insufficient to force the German army out of France; this was not because of poor generalship but due a form of warfare conducted with means made available by industrialisation, fought by closely matched opponents, who made mistakes but mostly fought with determination, using all the skill and technical measures they could find. The defensive methods used by the German army at Arras after 9 April were not superseded until changes were imposed by Ludendorff after the defeat at Broodseinde on 4 October. The British retained the strategic initiative but failed to capture the Belgian coast and the U-boat bases there, although after Broodseinde this was due more to the difficulties encountered by the British with the return of wet weather, than the effectiveness of German resistance.

The Battle of Cambrai showed continuity with the BEF's previous offensives in 1917. Novel features, mainly in the use of artillery, tank-infantry cooperation, airpower over the battlefield and the holding back of the assault divisions until just before the attack, resulted from the evolution of British technique. The experience of trying to move heavy artillery forward during the advance to the Hindenburg Line (Siegfriedstellung) in March was found particularly useful. Tanks were no longer unusual and their presence in large numbers left artillery free for neutralisation rather than destruction, particularly of barbed wire, which made the surprise attack feasible, given the success of the secret deployment of artillery reinforcements. The attempt to surprise the German defence, precluded extensive work on transport and supply infrastructure immediately behind the front, which caused the same sort of difficulties in maintaining momentum that crater fields did elsewhere in 1917. After the first couple of days the battle became another wearing-out operation, using up German reinforcements as they arrived, which when suspended on 28 November, gave the Germans time to mass for their counter-offensive of 30 November. More German forces were available due the closure of the eastern front and the end of the period when German forces were pinned down by the battle in Flanders. The course of the German counter-offensive, which was the biggest German attack in the west since Verdun in 1916, demonstrated that the constraints on advances encountered by the British and French armies were not unique. The ground gained in the German attack of 30 November was much less than intended and part of it was then lost to British counter-attacks. After this limited success, the fighting relapsed into another wearing-out fight, until the British abandoned their untenable salient at Bourlon Wood.

The significance of the Battle of Cambrai lay in the confounding of German defensive assumptions, by the British achievement of operational surprise for the first time since 1915. In the aftermath of the battle, "it was plain that the defensive must always contemplate the possibility of having large sections of the front broken, and of having to repair those breaches by considerable counter offensives....", this caused the German command to divert resources into anti-tank defences and end the skimping of artillery and ammunition supply in some areas to reinforce others, "Wherever the ground offers suitable going for tanks, surprise attacks like this may be expected... there can be no more mention of quiet fronts." (Rupprecht), this added to the German leadership's belief that a defensive strategy for 1918 would be impossible. The German commanders concluded that the speed of the cambrai counter-offensive had contributed to surprise but that last-minute changes to plans had diverted planning staffs from important details. Lack of time to study the ground and rehearse, had slowed the tempo of the attack and forced junior officers and NCO's to exercise conspicuous leadership, causing them heavy losses. The physical demands made on troops and horses, in travelling and marching for several days before the offensive, lessened the energy of their attack which rapidly broke down, many horses dying of exhaustion, which contributed to local ammunition shortages. The organisational feat of moving thirteen divisions to Cambrai between 20 and 30 November and another four by 2 December, in 1,163 trains and the achievement of surprise, brought the German army a considerable local success. The methods used by the Germans at Cambrai, were incorporated the manual for offensive operations Der Angriff im Stellungskrieg (The Attack in Position War) of January 1918, which laid down German offensive methods for the remainder of the war.