Division (military)

Divisions were the first regularly constituted military formation that combined infantry, artillery, and cavalry, an innovation of Napoleon Bonaparte. Before the invention of the division, commanders had to make ad hoc formations for every engagement, an especially challenging task since the modern staff had not been invented.

Napoleonic divisions were preconstituted, but did not have standardized mixtures of troops or equipment. The Duke of Wellington refined Napoleon's idea and created interchangeable divisions of standardized capabilities. Divisions were used in the American Civil War, but without significant standardization.

The Prussians, who were also refining the staff system, brought standarized division and a controlling staff together. The combination, organized by Helmuth von Moltke the Elder was a critical force multiplier for his troops in the Franco-Prussian War of 1871.

Divisions in the World Wars

By the First World War, divisions were quite standardized, although some were sufficiently large to be unwieldy. Depending on the country and branch of service, the chief unit of maneuver within a division was a regiment or brigade. The division also had supporting units such as artillery and engineers, which might be kept under central control or attached to maneuver units.

A popular organization of the time was a "square" division of four maneuver units. Sometimes, four regiments would be split into two brigades, which became the unit of action.

Higher-speed action in the Second World War led to "triangular" divisions of three regiments, where two regiments would assault and one would remain in reserve, waiting for a breach it could penetrate. In some armies, there might be three infantry and a tank regiment, or two infantry and one mechanized/motorized infantry unit. These were cases where the penetration unit was specialized for the purpose; foot-mobile infantry could create a breach for fast units, possibly with close air support, to exploit.

Divisions for breakthrough and penetration

The idea of specialist penetration units in the division led to the development of specialized divisions, as the penetration or pursuit formations at higher levels such as corps and army.

To help force that breach, the Soviet Union formed division-sized artillery formations, called "breakthrough artillery divisions".

Divisions for special operating environments

Several of the major powers in the Second World War organized parachute infantry divisions, also called airborne or paratroop. Given the limited capacity of troop-carrying aircraft, these divisions were very light in equipment, but posed a deeper threat than other formations. They were complemented by slightly heavier air-landing divisions, which expected to land on a newly captured airfield.

United States Marine Corps divisions specialized in amphibious assault, although U.K. and U.S. Army divisions were trained for specific landings, such as the Normandy Invasion.

Other light divisions specialized in mountain warfare.