Editing Division (military) (section)

=== World War II ===
The divisional system reached its numerical height during the [[Second World War]]. Beside the infantry and cavalry divisions created since Napoleonic era, new division types appeared during the Second World War, such as airborne, tank, mechanized, motorized.

The Soviet Union's [[Red Army]] consisted of more than a thousand division-sized units at any one time, and the number of rifle divisions raised during the [[Great Patriotic War]] of 1941–1945 is estimated{{by whom|date=April 2020}} at 2,000. [[Nazi Germany]] had hundreds of numbered or named divisions, while the United States employed up to 91 divisions.

A notable change to divisional structures during the war was completion of the shift from [[square division]]s (composed of two brigades each with two regiments) to [[triangular division]]s (composed of three regiments with no brigade level) that many European armies had started using in [[World War I]].<ref name=House>{{cite web |first= Jonathan M. |last= House |url= http://www-cgsc.army.mil/carl/resources/csi/House/House.asp |title= Toward Combined Arms Warfare: a Survey of 20th-Century Tactics, Doctrine, and Organization |date= 30 December 2009 |publisher= U.S. Army Command and General Staff College |url-status= dead |archive-url= https://web.archive.org/web/20091230072014/http://www-cgsc.army.mil/carl/resources/csi/House/House.asp |archive-date= 30 December 2009 }}</ref> This was done to increase flexibility and to pare down chain-of-command overhead. The triangular division structure allowed the tactic of "two forward, one back", where two of the division's regiments could engage the enemy with one regiment in reserve.

All divisions in World War II were expected to have their own artillery formations, usually (depending upon the nation) the size of a regiment. Divisional artillery was occasionally seconded by corps-level command to increase firepower in larger engagements.

During the war the US also used [[regimental combat team]]s, whereby attached and/or organic divisional units were parceled out to infantry regiments, creating smaller combined-arms units with their own armor and artillery and support units. These combat teams would still be under divisional command but had some level of autonomy on the battlefield.

'''Organic''' units within divisions were units which operated directly under divisional command and were not normally controlled by the regiments. These units were mainly support units in nature, and included signal companies, medical battalions, supply trains and administration.{{citation needed|date=April 2020}}

'''Attached''' units were smaller units that were placed under divisional command temporarily for the purpose of completing a particular mission. These units were usually combat units such as tank battalions, tank-destroyer battalions or cavalry-reconnaissance squadrons.