Strategic bombing during World War II

Strategic bombing during World War II defines any nations' government engaged in World War II undertaking independent air campaigns of a clearly recognisable strategic intent. This includes the sustained bombing of railways, harbours, cities (civilian areas), and industrial areas in enemy territory. The strategy is the air power theory that major victories can best be won by attacking the enemy's industrial and political infrastructure, rather than purely military targets. Strategic bombing is distinct from both close air support of ground forces and "tactical air power" (which is the battle for control of the air space.)

In 1939, Germany invaded Poland and the Luftwaffe (German air force) began providing close air support to the German Army. The Luftwaffe also began eliminating strategic objectives and bombing cities and civilian population in Poland in an indiscriminate and unrestricted aerial bombardment campaign. France and the United Kingdom declared war on Germany and the UK's Royal Air Force began attacking German warships along the German coast with the North Sea.

As the war continued to expand, bombing by both the Axis and Allied powers increased significantly. Military and industrial installations were targeted, but so were civilian populations in major war centres. Targeting cities and civilians was viewed as disrupting the control centre of the enemy, damaging his rail network, disrupting war industries, and as a psychological weapon to break the enemy's will to fight. From 1940–1941, Germany used this weapon in its 'Blitz' against Britain. From 1940 onward, the intensity of the British bombing campaign against Germany became less restrictive, increasingly targeting industrial sites and eventually, civilian areas. By 1943, the United States had significantly reinforced these efforts. The controversial firebombings of Hamburg (1943), Dresden (1945), and other German cities followed. The effect of strategic bombing varied depending on duration and intensity. Both the Luftwaffe and RAF failed to deliver a knockout blow by destroying enemy morale. However, strategic bombing of military targets could significantly reduce enemy industrial capacity and production.

In the Pacific War, the Japanese bombed Chongqing repeatedly until 1943. The U.S. strategic bombing of the Japanese Empire began in earnest in October 1944. Earlier, small-scale attacks by the U.S. out of China had been hampered by the task of delivering supplies over the Himalayas (known as "The Hump"). Missions out of the Mariana Islands escalated into widespread firebombing, which culminated in the atomic bombings of Hiroshima and Nagasaki on 6 and 9 August 1945 respectively, and the Japanese surrender on 15 August. In the opinion of inter-war proponents, the surrender of Japan vindicated strategic bombing.

Legal considerations
The Hague Conventions of 1899 and 1907, which address the codes of wartime conduct on land and at sea, were adopted before the rise of air power. Despite repeated diplomatic attempts to update international humanitarian law to include aerial warfare, it was not updated before the outbreak of World War II. The absence of specific international humanitarian law did not mean aerial warfare was not covered under the laws of war, but rather that there was no general agreement of how to interpret those laws. This means that aerial bombardment of civilian areas in enemy territory by all major belligerents during World War II was not prohibited by positive or specific customary international humanitarian law.

Many reasons exist for the absence of international law regarding aerial bombing in World War II. Most nations had refused to ratify such laws or agreements because of the vague or impractical wording in treaties such as the 1923 Hague Rules of Air Warfare. Also, the major powers' possession of newly developed advanced bombers was a great military advantage; they would not accept any negotiated limitations regarding this new weapon. In the absence of specific laws relating to aerial warfare, the belligerents' aerial forces at the start of World War II used the 1907 Hague Convention — signed and ratified by most major powers — as the customary standard to govern their conduct in warfare, and this convention was interpreted by both sides to allow the indiscriminate bombing of enemy cities throughout the war.

General Telford Taylor, Chief Counsel for War Crimes at the Nuremberg Trials, wrote that: "If the first badly bombed cities — Warsaw, Rotterdam, Belgrade, and London — suffered at the hands of the Germans and not the Allies, nonetheless the ruins of German and Japanese cities were the results not of reprisal but of deliberate policy, and bore witness that aerial bombardment of cities and factories has become a recognized part of modern warfare as carried out by all nations."

Article 25 of the 1899 and 1907 Hague Conventions on Land Warfare also did not provide a clear guideline on the extent to which civilians may be spared; the same can be held for naval forces. Consequently, cyclical arguments, such as those advanced by Italian general and air power theorist Giulio Douhet, do not appear to violate any of the Convention's provisions. Due to these reasons, the Allies at the Nuremberg and Tokyo Trials never criminalised aerial bombardment of non-military targets and Axis leaders who ordered a similar type of practice were not prosecuted. Chris Jochnick and Roger Normand in their article The Legitimation of Violence 1: A Critical History of the Laws of War explains that: "By leaving out morale bombing and other attacks on civilians unchallenged, the Tribunal conferred legal legitimacy on such practices."

Policy at the start of the war
Before World War II began, advances in aviation had led to a situation where groups of aircraft could devastate cities. This worrying development was compounded by the problem that the new aircraft flew at such altitudes that anti-aircraft guns were largely impotent and such speeds that ground based interceptors would be unlikely to be able to intercede. As British Prime Minister Stanley Baldwin warned in 1932, "The bomber will always get through".

When the war began on 1 September 1939, Franklin D. Roosevelt, President of the neutral United States, issued an appeal to the major belligerents (Britain, France, Germany, Italy and Poland) to confine their air raids to military targets, and "under no circumstances undertake bombardment from the air of civilian populations in unfortified cities" The British and French agreed to abide by the request, with the British reply undertaking to "confine bombardment to strictly military objectives upon the understanding that these same rules of warfare will be scrupulously observed by all their opponents". Germany also agreed to abide by Roosevelt's request and explained the bombing of Warsaw as within the agreement because it was supposedly a fortified city—Germany did not have a policy of targeting enemy civilians as part of their doctrine prior to World War II.

The British Government's policy was formulated on 31 August 1939: if Germany initiated unrestricted air action, the RAF "should attack objectives vital to Germany's war effort, and in particular her oil resources". If the Luftwaffe confined attacks to purely military targets, the RAF should "launch an attack on the German fleet at Wilhelmshaven" and "attack warships at sea when found within range". The government communicated to their French allies the intention "not to initiate air action which might involve the risk of civilian casualties"

While it was acknowledged bombing Germany would cause civilian casualties, the British government renounced deliberate bombing of civilian property, outside combat zones, as a military tactic. The British changed their policy on 15 May 1940, one day after the German bombing of Rotterdam, when the RAF was given permission to attack targets in the Ruhr Area, including oil plants and other civilian industrial targets which aided the German war effort, such as blast furnaces that at night were self-illuminating. The first RAF raid on the interior of Germany took place on the night of 15/16 May 1940 while the Battle of France was still continuing.

Poland
After the invasion of Poland, the Luftwaffe engaged in massive air raids against most Polish cities, destroying various infrastructure such as hospitals and schools. Civilians and refugees were also attacked. Notably, the Luftwaffe bombed Warsaw, Wieluń, and Frampol. It is believed that the bombing of Frampol was an experiment as it had no targetable industry and no military units were stationed there.

In his book, Eyes on the Sky, Wolfgang Schreyer wrote: "Frampol was chosen as an experimental object, because test bombers, flying at low speed, weren't endangered by AA fire. Also, the centrally placed town hall was an ideal orientation point for the crews. We watched possibility of orientation after visible signs, and also the size of village, what guaranteed that bombs nevertheless fall down on Frampol. From one side it should make easier the note of probe, from second side it should confirm the efficiency of used bombs."

The directives issued to the Luftwaffe for the Polish Campaign were to prevent the Polish Air Force from influencing the ground battles or attacking German territory. In addition, it was to support the advance of German ground forces through direct tactical and indirect air support with attacks against Polish mobilisation centres and thus delay an orderly Polish strategic concentration of forces and to deny mobility for Polish reinforcements through the destruction of strategic Polish rail routes.

Preparations were made for a concentrated attack (Operation Wasserkante) by all bomber forces against targets in Warsaw. However the operation was cancelled-according to Polish professor Tomasz Szarota due to bad weather conditions, while German author Boog claims it was possibly due to Roosevelt's plea to avoid civilian casualties; according to Boog the bombing of military and industrial targets within the Warsaw residential area called Praga was prohibited. Polish reports from the beginning of September note strafing of civilians by German attacks and bombing of cemeteries and marked hospitals (marking of hospitals proved counterproductive as German aircraft began to specifically target them, until hospitals were moved into the open to avoid such targeting), and indiscriminate attacks on fleeing civilians which according to professor Tomasz Szarota was a direct violation of the Hague Convention. Warsaw was first attacked by German ground forces on 9 September and was put under siege on 13 September. German author Boog claims that with the arrival of German ground forces, the situation of Warsaw changed; under the Hague Convention, the city could be legitimately attacked as it was a defended city in the front line that refused calls to surrender.

The bombing of the rail network, crossroads, and troop concentrations played havoc on Polish mobilisation, while attacks upon civilian and military targets in towns and cities disrupted command and control by wrecking the antiquated Polish signal network. Over a period of a few days, Luftwaffe numerical and technological superiority took its toll on the Polish Air Force. Polish Air Force bases across Poland were also subjected to Luftwaffe bombing from 1 September 1939.

On 13 September, following orders of the ObdL to launch an attack on Warsaw's Jewish Quarter, justified as being for unspecified crimes committed against German soldiers but probably in response to a recent defeat by Polish ground troops, and intended as a terror attack, 183 bomber sorties were flown with 50:50 load of high explosive and incendiary bombs, reportedly set the Jewish Quarter ablaze. On 22 September, Wolfram von Richthofen messaged, "Urgently request exploitation of last opportunity for large-scale experiment as devastation terror raid ... Every effort will be made to eradicate Warsaw completely". His request was rejected. However, Hitler issued an order to prevent civilians from leaving the city and to continue with the bombing, which he thought would encourage Polish surrender.

On 14 September, the French Air attaché in Warsaw reported to Paris, "the German Air Force acted in accordance to the international laws of war [...] and bombed only targets of military nature. Therefore, there is no reason for French retorsions." That day – the Jewish New Year – the Germans concentrated again on the Warsaw's Jewish population, bombing the Jewish quarter and targeting synagogues. According to professor Szarota the report was inaccurate-as its author Armengaud didn't knew about the most barbaric bombings like those in Wieluń or Kamieniec, left Poland on 12 September, and was motivated by his personal political goal to avoid French involvement in the war, in addition the report published in 1948 rather than in 1939.

Three days later, Warsaw was surrounded by the Wehrmacht, and hundreds of thousands of leaflets were dropped on the city, instructing citizens to evacuate the city pending a possible bomber attack. On 25 September the Luftwaffe flew 1,150 sorties and dropped 560 tonnes of high explosive and 72 tonnes of incendiaries. (Overall, incendiaries made up only three percent of the total tonnage dropped.)

To conserve the strength of the bomber units for the upcoming western campaign, the modern He 111 bombers were replaced by Ju 52 transports using "worse than primitive methods" for the bombing. Due to prevailing strong winds they achieved poor accuracy, even causing some casualties to besieging German troops.

The only Polish raid against a target in Germany was executed by PZL.23 Karaś light bombers against a factory in Ohlau. The Polish air force left Poland on 18 September 1939 due to the Soviet attack on 17 September 1939, and imminent capture of the Polish airstrips and aircraft stationed in eastern parts of Poland. There was no exception; even Pursuit Brigade, an organic part of the defences of the Polish capitol, Warsaw, was transferred to Lublin, one week into the war.

The Western Front, 1939 to June 1940
In 1939, following the German invasion of Poland, the United Kingdom and France declared war on Germany and the war in the West began. Britain attempted to bomb German warships and light vessels in several harbours on 3 and 4 September. Eight German Kriegsmarine men were killed at Wilhelmshaven – the war's first casualties to British bombs; attacks on ships at Cuxhaven and Heligoland followed. The 1939 Battle of the Heligoland Bight showed the vulnerability of bombers to fighter attack.

Germany's first strikes were not carried out until the 16 and 17 October 1939, against the British fleet at Rosyth and Scapa Flow. Little activity followed. Meanwhile, attacks by the Royal Air Force dwindled to less than one a month. As the winter set in, both sides engaged in propaganda warfare, dropping leaflets on the populations below. The Phony War continued.

The British government banned attacks on land targets and German warships in port due to the risk of civilian casualties. For the Germans, the earliest directive from the Luftwaffe head Hermann Göring permitted restricted attacks upon warships anywhere, as well as upon troop transports at sea. However, Hitler's OKW Direktive Nr 2 and Luftwaffe Direktive Nr 2, prohibited attacks upon enemy naval forces unless the enemy bombed Germany first, noting, "the guiding principle must be not to provoke the initiation of aerial warfare on the part of Germany."

After the Altmark Incident, the Luftwaffe launched a strike against the British navy yard at Scapa Flow on 16 March 1940, leading to the first British civilian death. A British attack followed against the German airbase at Hörnum on the island of Sylt, hitting a hospital, although there were no casualties. The Germans retaliated with a naval raid.

On 10 May 1940, Germany invaded Belgium, the Netherlands, and Luxembourg, intending to drive through the Ardennes into France and strike a quick blow that would end the war. This assault initiated the Battle of France. As it began, three German bombers from KG 51 mistakenly bombed the German city of Freiburg instead of the French airfield of Dole-Taveux, having lost their way over the Black Forest. The Germans reported it as an Allied 'terror attack', and not until 1956, when the mistake was brought to light by researchers, was the myth dispelled.

German bombing of France began on the night of 9/10 May. By 11 May, the French reported bombs dropped on Henin-Lietard, Bruay, Lens, La Fere, Loan, Nancy, Colmar, Pontoise, Lambersart, Lyons, Bouai, Hasebrouck, Doullens and Abbeville with at least 40 civilians killed.

On 12 May 1940, the British launched their first attacks on transport targets in the German industrial Ruhr Valley, including Cologne. While Allied light and medium bombers attempted to delay the German invasion by striking at troop columns and bridges, the British War Cabinet gave permission for limited bombing raids against targets such as roads and railways west of the River Rhine. The first British bombs fell on Mönchengladbach on the night of 11/12 May 1940, while Bomber Command was attempting to hit roads and rail near the Dutch-German border; four people were killed. Targets in Gelsenkirchen were attacked first on the 14/15 May.


 * Rotterdam Blitz

The Germans used the threat of bombing Rotterdam to try to get the Dutch to come to terms and surrender. After a second ultimatum had been issued by the Germans, it appeared their effort had failed and on 14 May 1940, Luftwaffe bombers were ordered to bomb Rotterdam in an effort to force the capitulation of the besieged city. The controversial bombing targeted the centre of the besieged city, instead of providing direct tactical support for the hard-pressed German 22nd Infantry Division (under Lt. Gen. von Sponeck, which had airlanded on 10 May) in combat with Dutch forces northwest of the city, and in the eastern part of the city at the Meuse river bridge. At the last minute, Holland decided to submit and sent a plenipotentiary and other negotiators across to German lines. There was an attempt to call off the assault, but the bombing mission had already begun. In legal terms, the attack was performed against a defended part of a city vital for the military objectives and in the front-line, and the bombing respected Article 25 to 27 of the Hague Conventions on Land Warfare.



Out of 100 Heinkel He 111s, 57 dropped their ordnance, a combined 97 tons of bombs. In the resulting fire 1.1 sqmi of the city centre were devastated, including 21 churches and 4 hospitals. The strike killed between 800–1,000 civilians, wounded over 1,000, and made 78,000 homeless. Nearly twenty-five thousand homes, 2,320 stores, 775 warehouses and 62 schools were destroyed.

Whilst German Historian Horst Boog says British propaganda inflated the number of civilian casualties by a factor 30, contemporary newspaper reports show the Dutch legation in Paris initially estimated 100,000 people were killed, the Dutch legation in New York later issued a revised figure of 30,000. International news agencies widely reported these figures, portraying Rotterdam as a city mercilessly destroyed by terror bombing without regard for civilian life, with 30,000 dead lying under the ruins. Neither claim was true. Furthermore, the bombing was against well-defined targets, albeit in the middle of the city, and would have assisted the advancing German Army. The Germans had threatened to bomb Utrecht in the same fashion, and the Netherlands surrendered.


 * British response

Following the attack on Rotterdam, RAF Bomber Command was authorized to attack German targets east of the Rhine on 15 May 1940; the Air Ministry authorized Air Marshal Charles Portal to attack targets in the Ruhr, including oil plants and other civilian industrial targets which aided the German war effort, such as blast furnaces (which at night were self-illuminating). The underlying motive for the attacks was to divert German air forces away from the land front. Churchill explained the rationale of his decision to his French counterparts in a letter dated the 16th: "I have examined today with the War Cabinet and all the experts the request which you made to me last night and this morning for further fighter squadrons. We are all agreed that it is better to draw the enemy on to this Island by striking at his vitals, and thus to aid the common cause." Due to the inadequate British bomb-sights the strikes that followed "had the effect of terror raids on towns and villages." On the night of 15/16 May, 96 bombers crossed the Rhine and attacked. 78 had been assigned oil targets, but only 24 claimed to have accomplished their objective. On the night of 17/18 May, RAF Bomber Command bombed oil installations in Hamburg and Bremen; the H.E. and 400 incendiaries dropped caused six large, one moderately large and 29 small fires. As a result of the attack, 47 people were killed and 127 were wounded. Railway yards at Cologne were attacked on the same night. During May, Essen, Duisburg, Düsseldorf and Hanover were attacked in a similar fashion by Bomber Command. In June, attacks were made on Dortmund, Mannheim, Frankfurt and Bochum. At the time, Bomber Command lacked the necessary navigational and bombing technical background and the accuracy of the bombings during the night attacks was abysmal. Consequently, the bombs were usually scattered over a large area, causing an uproar in Germany. Furthermore, on the night of 7/8 June 1940 a single French Navy Farman F.223 bomber attacked Berlin. The attack occurred just days after Germany had bombed Paris.

Despite the British attacks on German cities, the Luftwaffe did not begin to attack military and economic targets in the UK mainland until six weeks after the campaign in France had been concluded.

The Battle of Britain and the Blitz
On 22 June 1940, France signed an armistice with Germany. Britain was determined to keep fighting. On 1/2 July, the British attacked the German warships GERMAN BATTLESHIP Scharnhorst and GERMAN CRUISER Prinz Eugen in the port of Kiel and the next day, 16 RAF bombers attacked German train facilities in Hamm.

On 10 July, the Battle of Britain began with attack on shipping and fighter skirmishes over the British Channel. The battle began with probing attacks on British coastal shipping, during which Hitler called for the British to accept peace, but the British refused to negotiate.

Still hoping that the British would negotiate for peace, Hitler explicitly prohibited attacks on London and against civilians. Any airmen who, deliberately or unintentionally, violated this order were punished. Hitler's No. 17 Directive, issued 1 August 1940, established the conduct of war against Britain and specifically forbade the Luftwaffe from conducting terror raids. The Führer declared that terror attacks could only be a means of reprisal, as ordered by him. Hitler's instructions were echoed in Hermann Göring's general order, issued on 30 June 1940:

"The war against England is to be restricted to destructive attacks against industry and air force targets which have weak defensive forces. ... The most thorough study of the target concerned, that is vital points of the target, is a pre-requisite for success. It is also stressed that every effort should be made to avoid unnecessary loss of life amongst the civilian population."

- Hermann Göring

On 8 August 1940, the Germans switched to raids on RAF fighter bases. To reduce losses, the Luftwaffe also began to use increasing numbers of bombers at night. By the last week of August, over half the missions were flown under the cover of dark. On 24 August, fate took a turn, and several off-course German bombers accidentally bombed residential areas of London. The next day, the RAF bombed Berlin for the first time, targeting Tempelhof airfield and the Siemens factories in Siemenstadt. These attacks were seen as indiscriminate bombings by the Germans due to their inaccuracy, and this infuriated Hitler;  he ordered that the 'night piracy of the British' be countered by a concentrated night offensive against the island, and especially London. In a public speech in Berlin on 4 September 1940, Hitler announced that:

"The other night the English had bombed Berlin. So be it. But this is a game at which two can play. When the British Air Force drops 2000 or 3000 or 4000 kg of bombs, then we will drop 150 000, 180 000, 230 000, 300 000, 400 000 kg on a single night. When they declare they will attack our cities in great measure, we will eradicate their cities. The hour will come when one of us will break – and it will not be National Socialist Germany!"

- Adolf Hitler



The Luftwaffe, which Hitler had prohibited from bombing civilian areas in the UK, was now ordered to bomb British cities. The Blitz was underway. Göring – at Kesselring's urging and with Hitler's support- turned to a massive assault on the British capital. On 7 September, 318 bombers from the whole KG 53 supported by eight other Kampfgruppen, flew almost continuous sorties against London, the dock area which was already in flames from earlier daylight attacks. The attack of 7 September 1940 did not entirely step over the line into a clear terror bombing effort since its primary target was the London docks, but there was clearly an assumed hope of terrorizing the London population. Hitler himself hoped that the bombing of London would terrorize the population into submission. He stated that "If eight million [Londoners] go mad, it might very well turn into a catastrophe!". After that he believed "even a small invasion might go a long way". Another 250 bomber sorties were flown in the night. By the morning of the 8 September 430 Londoners had been killed. The Luftwaffe issued a press notice announcing they had dropped more than 1,000,000 kilograms of bombs on London in 24 hours. Many other British cities were hit in the nine-month Blitz, including Birmingham, Liverpool, Southampton, Manchester, Bristol, Belfast, Cardiff, Clydebank, Kingston upon Hull and Coventry. Sir Basil Collier, author of 'The Defence of the United Kingdom', the HMSO's official history, wrote:

"Although the plan adopted by the Luftwaffe early September had mentioned attacks on the population of large cities, detailed records of the raids made during the autumn and the winter of 1940–41 does not suggest that indiscriminate bombing of the civilians was intended. The points of aim selected were largely factories and docks. Other objectives specifically allotted to bomber-crews included the City of London and the governmental quarter rounds Whitehall."

- Sir Basil Collier

In addition to the conclusions of Sir Basil Collier to that effect there are also for example the 1949 memoirs of General Henry H. Arnold who had been in London 1941 and support Colliers estimate, and Harris noted in 1947 that the Germans had failed to take the opportunity to destroy English cities by concentrated incendiary bombing.

As the war continued, an escalating war of electronic technology developed. To counter German radio navigation aids, which helped their navigators find targets in the dark and through cloud cover, the British raced to work out the problems with countermeasures (most notably airborne radar, as well as highly effective deceptive beacons and jammers).

Despite causing a great deal of damage and disrupting the daily lives of the civilian population, the bombing of Britain failed to have an impact. British air defenses became more formidable, and attacks tapered off as Germany abandoned its efforts against Britain and focused more on the Soviet Union.

Operation Abigail Rachel was the bombing of Mannheim the "first deliberate terror raid" on Germany on 16 December. The British had been waiting for the opportunity to experiment with such a raid aimed at creating a maximum of destruction in a selected town since the summer 1940, and the opportunity was given after the German raid on Coventry. Internally it was declared to be a reprisal for Coventry and Southampton. The new bombing policy was officially ordered by Churchill at the start of December and the operation on condition it receive no publicity and be considered an experiment. Target marking missed the city centre and most bombs missed the city centre. This led to the development of the bomber stream. Despite the lack of decisive success of this raid, approval was granted for further Abigails.

This was the start of a British drift away from precision attacks on military targets and towards area bombing attacks on whole cities.

Germany later in the war
Due to the pre-war death of Generalleutnant Walther Wever in 1936, the primary proponent of a strategic bombing capability for Hitler's new air force, virtually nothing serious had been done with building any sort of truly-"four-engined" heavy bomber as the Allies possessed before the war began. The only "heavy bomber" design that would see service with the Luftwaffe in World War II – the trouble-prone Heinkel He 177A – had also been mistakenly meant by the RLM to have a medium angle "dive bombing" capability from the design's start in November 1937, something which Ernst Heinkel and Erhard Milch had vehemently disagreed with. The He 177A went into service in April 1942, despite an ongoing series of engine fires in the prototype series of aircraft, and the small batch of A-0 series production prototypes leading up to that timeframe – a serious-enough defeciency to lead Reichsmarschall Hermann Göring to decry the He 177A's pair of Daimler-Benz DB 606 powerplants to be nothing more than fire-prone, cumbersome "welded-together engines" in August of that year.

As the He 177As entered service in April 1942, following a destructive RAF attack on the Hanseatic medieval city of Lübeck, Adolf Hitler ordered the Luftwaffe to retaliate, leading to the so-called Baedeker Blitz: "The Führer has ordered that the air war against England be given a more aggressive stamp. Accordingly, when targets are being selected, preference is to be given to those where attacks are likely to have the greatest possible effect on civilian life. Besides raids on ports and industry, terror attacks of retaliatory nature are to be carried out against towns other than London. Minelaying is to be scaled down in favour of these attacks."

- Signal from the Führer's headquarters to the Luftwaffe High Command, 14 April 1942.

In January 1944, a beleaguered Germany tried to strike a blow to British morale with terror bombing with Operation Steinbock. At this stage of the war, Germany was critically short of heavy and medium bombers, with the added obstacles of a highly effective and sophisticated British air-defence system, and the increasing vulnerability of airfields in occupied Western Europe to Allied air attack making the effectiveness of German retaliation more doubtful.

However, German scientists had invented vengeance weapons – V-1 flying bombs and V-2 ballistic missiles – and these were used to launch an aerial assault on London and other cities in southern England from continental Europe. The campaign was much less destructive than the Blitz, so the British called it 'the Baby Blitz'. As the Allies advanced across France and towards Germany from the West, Paris, Liège, Lille and Antwerp also became targets.

The British and US directed part of the strategic bombing to the eradication of "wonder weapon" threats in what was later known as Operation Crossbow. The development of the V2 was hit preemptively in the British Peenemünde Raid (Operation Hydra) of August 1943.

British historian Frederick Taylor asserts that "all sides bombed each other's cities during the war. Half a million Soviet citizens, for example, died from German bombing during the invasion and occupation of Russia. That's roughly equivalent to the number of German citizens who died from Allied raids."

The British later in the war
The purpose of the area bombardment of cities was laid out in a British Air Staff paper, dated 23 September 1941: "The ultimate aim of an attack on a town area is to break the morale of the population which occupies it. To ensure this, we must achieve two things: first, we must make the town physically uninhabitable and, secondly, we must make the people conscious of constant personal danger. The immediate aim, is therefore, twofold, namely, to produce (i) destruction and (ii) fear of death."

During the first few months of the area bombing campaign, an internal debate within the British government about the most effective use of the nation's limited resources in waging war on Germany continued. Should the Royal Air Force (RAF) be scaled back to allow more resources to go to the British Army and Royal Navy or should the strategic bombing option be followed and expanded? An influential paper was presented to support the bombing campaign by Professor Frederick Lindemann, the British government's leading scientific adviser, justifying the use of area bombing to "dehouse" the German workforce as the most effective way of reducing their morale and affecting enemy war production.

Mr. Justice Singleton, a High Court Judge, was asked by Cabinet to look into the competing points of view. In his report, delivered on 20 May 1942, he concluded: "If Russia can hold Germany on land I doubt whether Germany will stand 12 or 18 months’ continuous, intensified and increased bombing, affecting, as it must, her war production, her power of resistance, her industries and her will to resist (by which I mean morale)."

In the end, thanks in part to the dehousing paper, it was this view which prevailed and Bomber Command would remain an important component of the British war effort up to the end of World War II. A very large proportion of the industrial production of the United Kingdom was harnessed to the task of creating a vast fleet of heavy bombers—so much so other vital areas of war production were under-resourced. Until 1944, the effect on German production was remarkably small and raised doubts whether it was wise to divert so much effort—the response being there was nowhere else the effort could have been applied, as readily, to greater effect.

Lindemann was liked and trusted by Winston Churchill, who appointed him the British government's leading scientific adviser with a seat in the Cabinet. In 1942, Lindemann presented the "dehousing paper" to the Cabinet showing the effect that intensive bombing of German cities could produce. It was accepted by the Cabinet, and Air Marshal Harris was appointed to carry out the task. It became an important part of the total war waged against Germany. Professor Lindemann's paper put forward the theory of attacking major industrial centres in order to deliberately destroy as many homes and houses as possible. Working-class homes were to be targeted because they had a higher density and fire storms were more likely. This would displace the German workforce and reduce their ability to work. His calculations (which were questioned at the time, in particular by Professor P. M. S. Blackett of the Admiralty operations research department, expressly refuting Lindemann's conclusions) showed the RAF's Bomber Command would be able to destroy the majority of German houses located in cities quite quickly. The plan was highly controversial even before it started, but the Cabinet thought that bombing was the only option available to directly attack Germany (as a major invasion of the continent was almost two years away), and the Soviets were demanding that the Western Allies do something to relieve the pressure on the Eastern Front. Few in Britain opposed this policy, but there were three notable opponents in Parliament, Bishop George Bell and the Labour MPs Richard Stokes and Alfred Salter. No effort to examine the effects of bombing was ever made.

On 14 February 1942, the Area bombing directive was issued to Bomber Command. Bombing was to be "focused on the morale of the enemy civil population and in particular of the industrial workers." Though it was never explicitly declared, this was the nearest that the British got to a declaration of unrestricted aerial bombing – Directive 22 said "You are accordingly authorised to use your forces without restriction", and then listing a series of primary targets which included Essen, Duisburg, Düsseldorf, and Cologne. Secondary targets included Braunschweig, Lübeck, Rostock, Bremen, Kiel, Hanover, Frankfurt, Mannheim, Stuttgart, and Schweinfurt. The directive stated that "operations should now be focused on the morale of the enemy civilian population, and in particular, the industrial workers". Lest there be any confusion, Sir Charles Portal wrote to Air Chief Marshal Norman Bottomley on 15 February "...I suppose it is clear that the aiming points will be the built-up areas, and not, for instance, the dockyards or aircraft factories". Factories were no longer targets.

The first true practical demonstrations were on the night of 28 to 29 March 1942, when 234 aircraft bombed the ancient Hanseatic port of Lübeck. This target was chosen not because it was a significant military target, but because it was expected to be particularly susceptible – in Harris's words it was "built more like a fire lighter than a city". The ancient timber structures burned well, and the raid destroyed most of the city's centre. A few days later, Rostock suffered the same fate.

At this stage of the air war, the most effective and disruptive examples of area bombing were the "thousand-bomber raids". Bomber Command was able by organization and drafting in as many aircraft as possible to assemble very large forces which could then attack a single area, overwhelming the defences. The aircraft would be staggered so that they would arrive over the target in succession: the new technique of the "bomber stream".

On 30 May 1942, between 0047 and 0225 hours, in Operation Millennium 1,046 bombers dropped over 2,000 tons of high explosive and incendiaries on the medieval town of Cologne, and the resulting fires burned it from end to end. The damage inflicted was extensive. The fires could be seen 600 miles away at an altitude of 20,000 feet. Some 3,300 houses were destroyed, and 10,000 were damaged. 12,000 separate fires raged destroying 36 factories, damaging 270 more, and leaving 45,000 people with nowhere to live or to work. Only 384 civilians and 85 soldiers were killed, but thousands evacuated the city. Bomber Command lost 40 bombers.

Two further thousand-bomber raids were conducted over Essen and Bremen, but neither so utterly shook both sides as the scale of the destruction at Cologne and Hamburg. The effects of the massive raids using a combination of blockbuster bombs (to blow off roofs) and incendiaries (to start fires in the exposed buildings) created firestorms in some cities. The most extreme examples of which were caused by Operation Gomorrah, the attack on Hamburg, (45,000 dead), attack on Kassel (10,000 dead), the attack on Darmstadt (12,500 dead), the attack on Pforzheim (21,200 dead), the attack on Swinemuende (23,000 dead) and the attack on Dresden (35,000 dead).

The effects of strategic bombing were very poorly understood at the time and grossly overrated. Particularly in the first two years of the campaign, few understood just how little damage was caused and how rapidly the Germans were able to replace lost production—despite the obvious lessons to be learned from the United Kingdom's own survival of the blitz. These problems were dealt with in two ways: first the precision targeting of vital facilities (ball-bearing production in particular) was abandoned in favour of "area bombing"—This change of policy was agreed by the Cabinet in 1941 and in early 1942 a new directive was issued and Air Marshal Arthur Harris (commonly known as "Bomber" Harris) was appointed to carry out the task—second as the campaign developed, improvements in the accuracy of the RAF raids were joined by better crew training, electronic aids, and new tactics such as the creation of a "pathfinder" force to mark targets for the main force, which was done over Harris' objections.

According to economic historian Adam Tooze, in his book The Wages of Destruction: The Making and Breaking of the Nazi Economy, a turning point in the bomber offensive was reached in March 1943, during the Battle of the Ruhr. Over five months 34,000 tons of bombs were dropped. Following the raids, steel production fell by 200,000 tons, making a shortfall of 400,000 tons. Speer acknowledged that the RAF were hitting the right targets, and raids severely disrupted his plans to increase production to meet increasing attritional needs. Between July 1943 and March 1944 there were no further increases in the output of aircraft.

The bombing of Hamburg in 1943 also produced impressive results. Tiger tank production, and the manufacture of 88mm guns, the most potent dual-purpose artillery piece in the Wehrmacht was "set back for months". On top of this, some 62 percent of the population was dehoused causing more difficulties. However, RAF Bomber Command allowed itself to be distracted by Harris' desire for a war winning blow, and attempted the fruitless missions to destroy Berlin and end the war by spring, 1944.

In October 1943, Harris urged the government to be honest with the public regarding the purpose of the bombing campaign. To Harris, his complete success at Hamburg confirmed the validity and necessity of his methods, and he urged that:

"the aim of the Combined Bomber Offensive...should be unambiguously stated [as] the destruction of German cities, the killing of German workers, and the disruption of civilized life throughout Germany. ... the destruction of houses, public utilities, transport and lives, the creation of a refugee problem on an unprecedented scale, and the breakdown of morale both at home and at the battle fronts by fear of extended and intensified bombing, are accepted and intended aims of our bombing policy. They are not by-products of attempts to hit factories."

By contrast, the United States Strategic Bombing Survey found attacks on waterways, beginning 23 September with strikes against the Dortmund-Ems Canal and Mittelland Canal, produced tremendous traffic problems on the Rhine River. It had immediate impacts on shipments of goods, and especially coal deliveries, upon which Germany's economy depended; with no more additional effort, by February 1945, rail transport (which competed for coal) had seen its shipments cut by more than half, and by March, "except in limited areas, the coal supply had been eliminated."

Other British efforts
Operation Chastise, better known as the Dambusters raid, was an attempt to damage German industrial production by crippling its hydro-electric power and transport in the Ruhr area. Operation Hydra of August 1943 sought to destroy German work on long-range rockets but only delayed it by a few months. Subsequent efforts were directed against V-weapon launch sites in France.

US bombing in Europe
In mid 1942, the United States Army Air Forces (USAAF) arrived in the UK and carried out a few raids across the English Channel. The USAAF Eighth Air Force's B-17 bombers were called the "Flying Fortresses" because of their heavy defensive armament of ten to twelve machine guns, and armor plating in vital locations. In part because of their heavier armament and armor, they carried smaller bomb loads than British bombers. With all of this, the USAAF's commanders in Washington, DC, and in Great Britain adopted the strategy of taking on the Luftwaffe head on, in larger and larger air raids by mutually defending bombers, flying over Germany, Austria, and France at high altitudes during the daytime. Also, both the U.S. Government and its Army Air Forces commanders were reluctant to bomb enemy cities and towns indiscriminately. They claimed that by using the B-17 and the Norden bombsight, the USAAF should be able to carry out "precision bombing" on locations vital to the German war machine: factories, naval bases, shipyards, railroad yards, railroad junctions, power plants, steel mills, airfields, etc.

In January 1943, at the Casablanca Conference, it was agreed RAF Bomber Command operations against Germany would be reinforced by the USAAF in a Combined Operations Offensive plan called Operation Pointblank. Chief of the British Air Staff MRAF Sir Charles Portal was put in charge of the "strategic direction" of both British and American bomber operations. The text of the Casablanca directive read: "Your primary object will be the progressive destruction and dislocation of the German military, industrial, and economic system and the undermining of the morale of the German people to a point where their capacity for armed resistance is fatally weakened.", At the beginning of the combined strategic bombing offensive on 4 March 1943, 669 RAF and 303 USAAF heavy bombers were available.

In the late 1943, the 'Pointblank' attacks manifested themselves in the infamous Schweinfurt raids (first and second). Formations of unescorted bombers were no match for German fighters, which inflicted a deadly toll. In despair, the Eighth halted air operations over Germany until a long-range fighter could be found in 1944; it proved to be the P-51 Mustang, which had the range to fly to Berlin and back.

USAAF leaders firmly held to the claim of "precision bombing" of military targets for much of the war, and dismissed claims they were simply bombing cities. However the American Eighth Air Force received the first H2X radar sets in December 1943. Within two weeks of the arrival of these first six sets, the Eighth command gave permission for them to area bomb a city using H2X and would continue to authorize, on average, about one such attack a week until the end of the war in Europe.

In reality, the day bombing was "precision bombing" only in the sense that most bombs fell somewhere near a specific designated target such as a railway yard. Conventionally, the air forces designated as "the target area" a circle having a radius of 1000 feet around the aiming point of attack. While accuracy improved during the war, Survey studies show that, in the over-all, only about 20% of the bombs aimed at precision targets fell within this target area. In the fall of 1944, only seven percent of all bombs dropped by the Eighth Air Force hit within 1,000 feet of their aim point.

Nevertheless, the sheer tonnage of explosive delivered by day and by night was eventually sufficient to cause widespread damage, and, more importantly from a military point of view, forced Germany to divert resources to counter it. This was to be the real significance of the Allied strategic bombing campaign—resource allocation. For the sake of improving the USAAF firebombing capabilities, a mock-up German Village was built up and repeatedly burned down. It contained full scale replicas of German residential homes. Firebombing attacks proved quite successful, in a single 1943 attack on Hamburg, roughly 50,000 civilians were killed and practically the entire city destroyed.



With the arrival of the brand-new Fifteenth Air Force based in Italy, command of the U.S. Air Forces in Europe was consolidated into the United States Strategic Air Forces (USSTAF). With the addition of the Mustang to its strength, the Combined Bomber Offensive was resumed. Planners targeted the Luftwaffe in an operation known as 'Big Week' (20–25 February 1944) and succeeded brilliantly – losses were so heavy German planners were forced into a hasty dispersal of industry and the day fighter arm never fully recovered.

On 27 March 1944, the Combined Chiefs of Staff issued orders granting control of all the Allied air forces in Europe, including strategic bombers, to General Dwight D. Eisenhower, the Supreme Allied Commander, who delegated command to his deputy in SHAEF Air Chief Marshal Arthur Tedder. There was resistance to this order from some senior figures, including Winston Churchill, Harris, and Carl Spaatz, but after some debate, control passed to SHAEF on 1 April 1944. When the Combined Bomber Offensive officially ended on 1 April, Allied airmen were well on the way to achieving air superiority over all of Europe. While they continued some strategic bombing, the USAAF along with the RAF turned their attention to the tactical air battle in support of the Normandy Invasion. It was not until the middle of September that the strategic bombing campaign of Germany again became the priority for the USSTAF.

The twin campaigns—the USAAF by day, the RAF by night—built up into massive bombing of German industrial areas, notably the Ruhr, followed by attacks directly on cities such as Hamburg, Kassel, Pforzheim, Mainz and the often-criticized bombing of Dresden.

Bombing in France
German-occupied France contained a number of important targets that attracted the attention of the British, and later American bombing. In 1940, RAF Bomber Command launched attacks against German preparations for Operation Sealion, the proposed invasion of England, attacking Channel Ports in France and Belgium and sinking large numbers of barges that had been collected by the Germans for use in the invasion. France's Atlantic ports were important bases for both German surface ships and submarines, while French industry was an important contributor to the German war effort.

Before 1944, the Allies bombed targets in France that were part of the German war industry. This included raids such as those on the Renault factory in Boulogne-Billancourt in March 1942 or the port facilities of Nantes in September 1943 (which killed 1,500 civilians). In preparation of Allied landings in Normandy and those in the south of France, French infrastructure (mainly rail transport) was intensively targeted by RAF and USAAF in May and June 1944. Despite intelligence provided by the French Resistance, many residential areas were hit in error or lack of accuracy. This included cities like Marseille (2,000 dead), Lyon (1,000 dead), Saint-Etienne, Rouen, Orléans, Grenoble, Nice, Paris surrounds, and so on. The Free French Air Force, operational since 1941, used to opt for the more risky skimming tactic when operating in national territory, to avoid civilian casualties. In 5 January 1945, British bombers struck the "Atlantic pocket" of Royan and destroyed 85% of this city. A later raid, using napalm was carried out before it was freed from Nazi occupation in April. Of the 3,000 civilians left in the city, 442 died.

French civilian casualties due to Allied strategic bombing are estimated at about half of the 67,000 French civilian dead during Allied operations in 1942–1945; the other part being mostly killed during tactical bombing in the Normandy campaign. 22% of the bombs dropped in Europe by British and American air forces between 1940 and 1945 were in France. The port city of Le Havre has been destroyed by 132 bombings during the war (5,000 dead) until September 1944. It has been rebuilt by architect Auguste Perret and is now a World Heritage Site.

Effectiveness
Strategic bombing has been criticized on practical grounds because it does not always work predictably. The radical changes it forces on a targeted population can backfire, including the counterproductive result of freeing inessential labourers to fill worker shortages in war industries.

Much of the doubt about the effectiveness of the bomber war comes from the oft-stated fact German industrial production increased throughout the war. Until late in the war, industry had not been geared for war and German factories only worked a single shift. Simply by going to three shifts, production could have been tripled with no change to the infrastructure. However, attacks on the infrastructure were taking place. The attacks on Germany's canals and railroads made transportation of materiel difficult.

The attack on oil production, oil refineries, and tank farms was, however, extremely successful and made a very large contribution to the general collapse of Germany in 1945. In the event, the bombing of oil facilities became Albert Speer's main concern; however, this occurred sufficiently late in the war that Germany would soon be defeated in any case. Nevertheless, it is fair to say the oil bombing campaign materially shortened the war, thereby saving many lives.

German insiders credit the Allied bombing offensive with crippling the German war industry. Speer repeatedly said (both during and after the war) it caused crucial production problems. Admiral Karl Dönitz, head of the U-boat fleet (U-waffe), noted in his memoirs failure to get the revolutionary Type XXI U-boats (which could have completely altered the balance of power in the Battle of the Atlantic) into service was entirely the result of the bombing. The United States Strategic Bombing Survey (Europe), says, despite bombing becoming a major effort, between December 1942 and June 1943, "The attack on the construction yards and slipways was not heavy enough to be more than troublesome" and the delays in delivery of Type XXIs and XXIIIs up until November 1944 "cannot be attributed to the air attack", but adds, "The attacks during the late winter and early spring of 1945 did close, or all but close, five of the major yards, including the great Blohm and Voss plant at Hamburg".

Effect on morale


Although designed to "break the enemy's will", the opposite often happened. The British did not crumble under the German Blitz and other air raids early in the war. British workers continued to work throughout the war and food and other basic supplies were available throughout.

The impact of bombing on German morale was significant according to Professor John Buckley. Around a third of the urban population under threat of bombing had no protection at all. Some of the major cities saw 55–60 percent of dwellings destroyed. Mass evacuations were a partial answer for six million civilians, but this had a severe impact on morale as German families were split up to live in difficult conditions. By 1944 absenteeism rates of 20–25 percent were not unusual and in post-war analysis 91 percent of civilians stated bombing was the most difficult hardship to endure and was the key factor in the collapse of their own morale. The United States Strategic Bombing Survey concluded that the bombing was not stiffening morale but seriously depressing it; fatalism, apathy, defeatism were apparent in bombed areas. The Luftwaffe was blamed for not warding off the attacks and confidence in the Nazi regime fell by 14 percent. Some 75 percent of Germans believed the war was lost in the spring of 1944, owing to the intensity of the bombing.

Buckley argues the German war economy did indeed expand significantly following Albert Speer’s appointment as Reichsminister of Armaments, "but it is spurious to argue that because production increased then bombing had no real impact". But the bombing offensive did do serious damage to German production levels. German tank and aircraft production, though reached new records in production levels in 1944, was in particular one-third lower than planned. In fact, German aircraft production for 1945 was planned at 80,000, "which gives an idea of direction Erhard Milch and the German planners were pushing", "unhindered by Allied bombing German production would have risen far higher".

Journalist Max Hastings and the authors of the official history of the bomber offensive, Noble Frankland among them, has argued bombing had a limited effect on morale. In the words of the British Bombing Survey Unit (BBSU): "The essential premise behind the policy of treating towns as unit targets for area attack, namely that the German economic system was fully extended, was false." This, the BBSU noted, was because official estimates of German war production were "more than 100 percent in excess of the true figures". The BBSU concluded: "Far from there being any evidence of a cumulative effect on (German) war production, it is evident that, as the (bombing) offensive progressed ... the effect on war production became progressively smaller (and) did not reach significant dimensions."

Casualties
After the war, the U.S. Strategic Bombing Survey reviewed the available casualty records in Germany, and concluded that official German statistics of casualties from air attack had been too low. The survey estimated that at a minimum 305,000 were killed in German cities due to bombing and estimated a minimum of 780,000 wounded. Roughly 7,500,000 German civilians were also rendered homeless. (see Dehousing).

In addition to the minimum figure given in the Strategic bombing survey, the number of people killed by Allied bombing in Germany has been estimated at between 400,000 and 600,000. In the UK, 60,595 British were killed by German bombing, and in France, 67,078 French were killed by US-UK bombing.

Belgrade was heavily bombed by the Luftwaffe on 6 April 1941, when more than 17,000 people were killed. According to The Oxford companion to World War II, "After Italy's surrender the Allies kept up the bombing of the northern part occupied by the Germans and more than 50,000 Italians were killed in these raids."

Over 160,000 Allied airmen were lost in the European theatre.

Asia
Within Asia, the majority of strategic bombing was carried out by the Japanese and the US. The British Commonwealth planned that once the war in Europe was complete, a strategic bombing force of up to 1,000 heavy bombers ("Tiger Force") would be sent to the Far East. This was never realised before the end of the Pacific War.

Japanese bombing
Japanese strategic bombing was independently conducted by the Imperial Japanese Navy Air Service and the Imperial Japanese Army Air Service. Bombing efforts mostly targeted large Chinese cities such as Shanghai, Wuhan, and Chongqing, with around 5,000 raids from February 1938 to August 1943 in the later case.

The bombing of Nanjing and Canton, which began on 22 and 23 September 1937, called forth widespread protests culminating in a resolution by the Far Eastern Advisory Committee of the League of Nations. Lord Cranborne, the British Under-Secretary of State For Foreign Affairs, expressed his indignation in his own declaration. "Words cannot express the feelings of profound horror with which the news of these raids had been received by the whole civilized world. They are often directed against places far from the actual area of hostilities. The military objective, where it exists, seems to take a completely second place. The main object seems to be to inspire terror by the indiscriminate slaughter of civilians..."

- Lord Cranborne

There were also air raids on Philippines and northern Australia (Bombing of Darwin, 19 February 1942). The Imperial Japanese Navy Air Service used tactical bombing against enemy airfields and military positions, as at the attack on Pearl Harbor. The Imperial Japanese Army Air Service also attacked enemy ships and military installations.

United States bombing of Japan
The United States strategic bombing of Japan took place between 1942 and 1945. In the last seven months of the campaign, a change to firebombing resulted in great destruction of 67 Japanese cities, as many as 500,000 Japanese deaths and some 5 million more made homeless. Emperor Hirohito's viewing of the destroyed areas of Tokyo in March 1945 is said to have been the beginning of his personal involvement in the peace process, culminating in Japan's surrender five months later.

Conventional bombing


The first U.S. raid on the Japanese main island was the Doolittle Raid of 18 April 1942 when sixteen B-25 Mitchells were launched from the USS Hornet (CV-8) to attack targets including Yokohama and Tokyo and then fly on to airfields in China. The raids were military pin-pricks, but a significant propaganda victory. Launched prematurely, none of the attacking aircraft reached the designated post mission airfields, either crashing or ditching (except for one aircraft, which landed in the Soviet Union, where the crew was interned). Two crews were captured by the Japanese.

The key development for the bombing of Japan was the B-29 Superfortress, which had an operational range of 1,500 miles (2,400 km); almost 90% of the bombs dropped on the home islands of Japan were delivered by this type of bomber (147,000 tons). The first raid by B-29s on Japan from China was on 15 June 1944. The B-29s took off from Chengdu, over 1,500 miles away. This first raid was also not particularly damaging to Japan. Only forty-seven of the sixty-eight bombers that took off hit the target area; four aborted with mechanical problems, four crashed, six jettisoned their bombs because of mechanical difficulties, and others bombed secondary targets or targets of opportunity. Only one B–29 was lost to enemy aircraft. The first raid from the east was on 24 November 1944 when 88 aircraft bombed Tokyo. The bombs were dropped from around 30,000 feet (10,000 m) and it is estimated that only around 10% of the bombs hit designated targets.

The initial raids were carried out by the Twentieth Air Force operating out of mainland China in Operation Matterhorn under XX Bomber Command. Initially the Twentieth Air Force was under the command of Hap Arnold, and later Curtis LeMay. This was never a satisfactory arrangement because not only were the Chinese airbases difficult to supply&mdash;materiel being sent by air from India over "the Hump"&mdash;but the B-29s operating from them could only reach Japan if they traded some of their bomb load for extra fuel in tanks in the bomb-bays. When Admiral Chester Nimitz's island-hopping campaign captured islands close enough to Japan to be within the range of B-29s, the Twentieth Air Force was assigned to XXI Bomber Command which organized a much more effective bombing campaign of the Japanese home islands. Based in the Marianas (Guam and Tinian in particular) the B-29s were now able to carry their full bomb loads and were supplied by cargo ships and tankers.

Unlike all other forces in theater, the USAAF Bomber Commands did not report to the commanders of the theaters but directly to the Joint Chiefs of Staff. In July 1945, they were placed under the U.S. Strategic Air Forces in the Pacific which was commanded by General Carl Spaatz.

As in Europe, the United States Army Air Forces (USAAF) tried daylight precision bombing. However, it proved to be impossible due to the weather around Japan, "during the best month for bombing in Japan, visual bombing was possible for [just] seven days. The worst had only one good day." Further, bombs dropped from a great height were tossed about by high winds.

General LeMay, commander of XXI Bomber Command, instead switched to mass firebombing night attacks from altitudes of around 7,000 feet (2,100 m) on the major conurbations. "He looked up the size of the large Japanese cities in the World Almanac and picked his targets accordingly." Priority targets were Tokyo, Nagoya, Osaka, and Kobe. Despite limited early success, particularly against Nagoya, LeMay was determined to use such bombing tactics against the vulnerable Japanese cities. Attacks on strategic targets also continued in lower-level daylight raids.

The first successful firebombing raid was on Kobe on 3 February 1945, and following its relative success the USAAF continued the tactic. Nearly half of the principal factories of the city were damaged, and production was reduced by more than half at one of the port's two shipyards.

Much of the armor and defensive weaponry of the bombers was removed to allow increased bomb loads; Japanese air defense in terms of night-fighters and anti-aircraft guns was so feeble it was hardly a risk. The first raid of this type on Tokyo was on the night of 23–24 February when 174 B-29s destroyed around one square mile (3 km²) of the city. Following on that success, as Operation Meetinghouse, 334 B-29s raided on the night of 9–10 March, dropping around 1,700 tons of bombs. Around 16 square miles (41 km²) of the city was destroyed and over 100,000 people are estimated to have died in the fire storm. The destruction and damage was at its worst in the city sections east of the Imperial Palace. It was the most destructive conventional raid, and the deadliest single bombing raid of any kind in terms of lives lost, in all of military aviation history. The city was made primarily of wood and paper, and Japanese firefighting methods were not up to the challenge. The fires burned out of control, boiling canal water and causing entire blocks of buildings to spontaneously combust from the heat. The effects of the Tokyo firebombing proved the fears expressed by Admiral Yamamoto in 1939: "Japanese cities, being made of wood and paper, would burn very easily. The Army talks big, but if war came and there were large-scale air raids, there's no telling what would happen."

In the following two weeks, there were almost 1,600 further sorties against the four cities, destroying 31 square miles (80 km²) in total at a cost of 22 aircraft. By June, over forty percent of the urban area of Japan's largest six cities (Tokyo, Nagoya, Kobe, Osaka, Yokohama, and Kawasaki) was devastated. LeMay's fleet of nearly 600 bombers destroyed tens of smaller cities and manufacturing centres in the following weeks and months.

Leaflets were dropped over cities before they were bombed, warning the inhabitants and urging them to escape the city. Though many, even within the Air Force, viewed this as a form of psychological warfare, a significant element in the decision to produce and drop them was the desire to assuage American anxieties about the extent of the destruction created by this new war tactic. Warning leaflets were also dropped on cities not in fact targeted, to create uncertainty and absenteeism.

A year after the war, the U.S. Strategic Bombing Survey (Pacific War) reported they had underestimated the power of strategic bombing combined with naval blockade and previous military defeats to bring Japan to unconditional surrender without invasion. By July 1945, only a fraction of the planned strategic bombing force had been deployed yet there were few targets left worth the effort. In hindsight, it would have been more effective to use land-based and carrier-based air power to strike merchant shipping and begin aerial mining at a much earlier date so as to link up with effective submarine anti-shipping campaign and completely isolate the island nation. This would have accelerated the strangulation of Japan and ended the war sooner. A postwar Naval Ordnance Laboratory survey agreed, finding naval mines dropped by B-29s had accounted for 60% of all Japanese shipping losses in the last six months of the war. In October 1945, Prince Fumimaro Konoe said the sinking of Japanese vessels by U.S. aircraft combined with the B-29 aerial mining campaign were just as effective as B-29 attacks on industry alone, though he admitted, "the thing that brought about the determination to make peace was the prolonged bombing by the B-29s." Prime Minister Baron Kantarō Suzuki reported to U.S. military authorities it "seemed to me unavoidable that in the long run Japan would be almost destroyed by air attack so that merely on the basis of the B-29s alone I was convinced that Japan should sue for peace."

Nuclear bombing


After six months of intense firebombing of 67 other Japanese cities, the United States under President Harry Truman conducted nuclear attacks on the Empire of Japan.

On 6 August 1945, the "Little Boy" enriched uranium nuclear bomb was dropped on the city of Hiroshima, followed on 9 August by the detonation of the "Fat Man" plutonium core nuclear bomb over Nagasaki. To date, these are the only uses of nuclear weapons in warfare.

The physical destruction in Hiroshima amounted to 90% of the area, and in Nagasaki 45%. By the end of 1945, as many as 140,000 people in Hiroshima and 80,000 in Nagasaki were dead from the attacks, roughly half of the residential populations on the days of the bombings. Thousands more have been subsequently killed from injuries or the combined effects of flash burns, trauma, and radiation burns, compounded by illness, malnutrition and radiation sickness. Since then more have died from leukemia and solid cancers attributed to exposure to radiation released by the bombs. In both cities, the overwhelming majority of the dead were civilians.

On 15 August 1945, Japan announced its surrender to the Allied Powers, signing the Instrument of Surrender on 2 September which officially ended World War II. Furthermore, the experience of bombing led post-war Japan to adopt Three Non-Nuclear Principles, which forbade Japan from nuclear armament.