Combined arms

Combined arms is an approach to warfare which seeks to integrate different combat arms of a military to achieve mutually complementary effects (for example, using infantry and armor in an urban environment, where one supports the other, or both support each other). Combined arms doctrine contrasts with segregated arms where each military unit is composed of only one type of soldier or weapon system. Segregated arms is the traditional method of unit/force organisation, employed to provide maximum unit cohesion and concentration of force in a given weapon or unit type.

Though the lower-echelon units of a combined arms team may be of similar types, a balanced mixture of such units are combined into an effective higher-echelon unit, whether formally in a table of organization or informally in an ad hoc solution to a battlefield problem. For example an armored division — the modern paragon of combined arms doctrine — consists of a mixture of infantry, tank, artillery, reconnaissance, and perhaps even helicopter units, all coordinated and directed by a unified command structure.

Also, most modern military units can, if the situation requires it, call on yet more branches of the military, such as fighter or bomber aircraft or naval forces, to support their operations. The mixing of arms is sometimes pushed down below the level where homogeneity ordinarily prevails, for example by temporarily attaching a tank company to an infantry battalion.

Ancient warfare
Combined arms operations dates back to antiquity, where armies would usually field a screen of skirmishers to protect their spearmen during the approach to contact. Especially in the case of the Greek hoplites however, the focus of military thinking lay almost exclusively on the heavy infantry. In more elaborate situations armies of various nationalities fielded different combinations of light, medium, or heavy infantry, cavalry, chariotry, camelry, elephantry, and artillery (mechanical weapons); the ancient Persian army is an excellent example of this. Combined arms in this context was how to best use the cooperating units, variously armed with side-arms, spears, or missile weapons in order to coordinate an attack in time and space that would best disrupt and then destroy the enemy.

Philip II of Macedon greatly improved upon the limited combined arms tactics of the Greek city-states and combined the newly created Macedonian Phalanx with heavy cavalry and other forces. The Phalanx would hold the opposing line in place, until the heavy cavalry could smash and break the enemy line by achieving local superiority.

The pre-Marian Roman Legion was a combined arms force and consisted of five classes of troops. Lightly equipped velites acted as skirmishers armed with light javelins. The hastati and principes formed the main attacking strength of the legion with sword and pilum, whilst the triarii formed the defensive backbone of the legion fighting as a phalanx with long spears and large shields. The fifth class were the equites, the cavalry, used for scouting, pursuit and to guard the flanks.

After the Marian reforms the Legion was notionally a unit of heavy infantrymen armed with just sword and pilum, and fielded with a small attached auxiliary skirmishers and missile troops, and incorporated a small cavalry unit.

The legion was sometimes also incorporated into a higher-echelon combined arms unit, e.g. in one period it was customary for a general to command two legions plus two similarly sized units of auxiliaries, lighter units useful as screens or for combat in rough terrain.

The army of the Han Dynasty is also an example, fielding melee infantry, crossbowmen, and cavalry (ranging from horse archers to heavy lancers).

Civilizations such as the Carthaginians and Sassanids also were known to have fielded a combination of infantry supported by powerful cavalry.

Middle Ages
In the 6th century, the Byzantine emperor Maurice I wrote the Strategikon, a manual of war that codified a number of military reforms of the time. These reforms would remain relatively unchanged for 500 years. Today, the Strategikon is considered the first sophisticated formulation of combined arms theory.

The English victories of Crecy, Poitiers and Agincourt were examples of a simple form of combined arms, with a combination of dismounted knights forming a foundation for formations of English longbowmen. The lightly protected longbowmen could down their French opponents at a distance, whilst the armoured men-at-arms could deal with any Frenchmen who made it to the English lines. This is the crux of combined arms: to allow a combination of forces to achieve what would be impossible for its constituent elements to do alone.

During the late Middle Ages in Western Europe, fighting men were principally organized on the basis of a combined arms team, or a Lance. The Lance consisted of a landholder and the men in his direct service: the men he rode to war with. The classic example of a Lance, as in the royal French and their opposing Burgundian forces, featured one noble heavy cavalryman, commonly known as a Knight, supported by at least two Sergeants (professional soldiers, as opposed to gentry, who carried similar arms as knights, only lighter and cheaper), two mounted archers, and between two and six valets or squires, non-combatant support troops in the service of the knight.

As the vast majority of Medieval European warfare consisted of performing raids and long-range patrols, the lance was an important method of providing shock effect, ranged firepower, and logistical support for a knightly retinue out for plunder. For the rare occurrence of a set-piece battle, the most senior of the gentry would break up the lances, organizing the men into the more familiar en bloc formation of individual arms: sergeants dismounting to form the main battle line with archers and crossbowmen in support.

The knights would remain mounted and act as scouts, flank defense, and in rare instances, the main frontal assault force. The Sergeants, also known as Men-At-Arms, were principally professional soldiers of common birth, although this was not always the case. As the number of truly professional soldiers was very low, the Lances were often supplemented by large numbers of drafted peasants, local Militia  and mercenaries.

The shortcomings of early firearms forced the Spanish Army to adopt the combined arms tercio. The slow firing arquebusers being protected by pikemen and the cumbersome pikemen in turn protected by agile sword and buckler men. The success of the tercio inspired similar formations and tactics being adopted by the armies of other nations.

For example the English New Model Army consisted of intermixed musketeers and pikemen forming a base of manoeuvre for cavalry.

The massed tercio declined with improvements in artillery, for smaller more flexible units. As muskets improved, the ratio of pikes to muskets declined until with the invention of the bayonet, their number was reduced to a handful of shortened partisans which were retained only as badges of rank.

17th to 19th centuries
17th century saw increasing use of combined arms at lower (regimental) level. King Gustavus Adolphus of Sweden was the proponent of the idea. For fire support he attached teams of "commanded musketeers" to cavalry units and fielded light 3-pounder guns to provide infantry units with organic artillery.

In Japan, in battle of Nagashino (長篠の戦い) in 1575, forces of Oda clan successfully employed combined arms against Takeda clan army which heavily relied on cavalry. The Oda army erected palisades to protect their ashigaru musketeers that downed Takeda's cavalry while their samurai cut down any enemies who managed to approach melee range.

In the eighteenth century, the concept of the legion was revived. Legions now consisted of musketeers, light infantry, dragoons and artillery in a brigade sized force. These legions often combined professional military personnel with militia. Perhaps the most notable example is the use of light cavalry, light infantry and light horse artillery in advance detachments by France's La Grande Armée during the Napoleonic Wars. This was not a new idea, having been used by the Imperial Russian Army's use of cossacks.

The use of light mobile troops in bringing about decisive action next saw application during the American Civil War where both sides combined the speed of cavalry and the firepower of the infantry to use mounted infantry in conducting deep raids into the enemy rear, sabotaging the logistics (often railway lines) to affect the supply of frontline troops.

The need for manoeuvre was emphasized by the American Civil War, and was used very effectively by the Prussian General Staff to combine the strategic use of railways with the new firepower of quick-firing ordnance and small arms to defeat France in 1871.

20th-century developments
The development of modern combined arms tactics began in the First World War. Early in the war, fighting descended into stagnant trench warfare. Generals on both sides applied conventional military thinking to the new weapons and situations that they faced. In these early stages, tactics typically comprised heavy artillery barrages followed by massed frontal assaults against well entrenched enemies. These tactics were largely unsuccessful and resulted in large loss of life.

As the war progressed new combined arms tactics were developed, often described then as the "all arms battle". These included direct close artillery fire support for attacking soldiers (the creeping barrage), air support and mutual support of tanks and infantry. One of the first instances of combined arms was the Battle of Cambrai, in which the British used tanks, artillery, infantry, small arms and air power to break through enemy lines. Previously such a battle would have lasted months with many hundreds of thousands of casualties. Co-ordination and pre-planning were the key elements, and the use of combined arms tactics in the Hundred Days Offensive in 1918 allowed the Allied forces to exploit breakthroughs in the enemy trenches, forcing the surrender of the Central Powers.

After the First World War there was a significant degree of experimentation with the new technologies, including in the UK, France and the Soviet Union. By the late 1930s it was the Soviet military theoreticians who had developed and implemented a fully integrated combined arms doctrine with some cooperation by the German Reich's Wehrmacht. In fact the implementation was so widespread that the Red Army's armies were known as Combined Arms (Общевойсковая) armies to distinguish them from the Tank Army. Some 95 of these were formed during WWII.

The Soviet doctrine continued in development after the end of WWII, and in attempting to further integrate the Arms and Services in combat had by early 1960s developed the first Infantry Fighting Vehicle in the shape of the BMP-1.

In 1963 the United States Marine Corps formalized the concept of the Marine Air-Ground Task Force, which combined Marine aviation and Marine ground units for expeditionary missions.

The Vietnam War had a profound influence on the development of the US Army's combined arms doctrine. Due to the very difficult terrain that prevented access to the enemy held areas of operation, troops were often deployed by air assault. For this reason, US troops in Vietnam saw six times more combat than in preceding wars, due to less time spent on logistic delays. The result; an infantry unit increased in effectiveness by a factor of four for its size, when supported with helicopter-delivered ammunition, food and fuel. In time the US Army in Vietnam also learned to combine helicopter operations and airmobile infantry with the armoured and artillery units operating from fire support bases as well as the US brown-water navy and USAF Close Air Support units supporting them.

In the Soviet-Afghanistan war, helicopters were treated much like flying light tanks. They were almost always the first assault element to make contact in a battle, and often the most effective. Titanium and composite armor made them less vulnerable to fire from small arms. Although the Soviet Army proved effective in its operations as independent unit in combined arms operations, the social nature of the conflict, the terrain and the inadequate logistics crippled overall effort by the 40th Army command, eventually forcing a withdrawal of Soviet troops from Afghanistan.

Post Cold War (1991 to Present)
In the 1991 Gulf War a mix of strikes by fixed-wing aircraft including carpet bombing and precision bombing was used in combination with large numbers of strikes by attack helicopters. During the ground assault phase tanks and other AFV's supported by attack aircraft swept over remaining forces. The front moving line moved forward at upwards of 40–50 km/h at the upper limit of the Army's tracked vehicles.

In 2000, the US Army began developing a new set of doctrines intended to use information superiority to wage warfare. Six pieces of equipment were crucial for this: AWACS, an air-borne look-down radar JSTARS, GPS, the lowly SINCGARS VHF digital radio, and ruggedized PCs. The mix is supplemented by satellite photos and passive reception of enemy radio emission, forward observers with digital target designation, specialized scouting aircraft, anti-artillery radars and gun-laying software for artillery. Everything feeds the network.

Based on this doctrine, many U.S. ground vehicles moved across the landscape alone. If they encountered an enemy troop or vehicle concentration, they would assume a defensive posture, lay down as much covering fire as they could, designate the targets for requested air and artillery assets. Within a few minutes, on station aircraft would direct their missions to cover the ground vehicle. Within a half hour heavy attack forces would concentrate to relieve the isolated vehicle. In an hour and a half the relieved vehicle would be resupplied.

In 2011, Russia began organizing into a Combined Arms military.