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.