Triangular division

A triangular division is a designation given to the way military divisions are organized. In a triangular organization, the division's main body is composed of three regimental maneuver elements. These regiments may be controlled by a brigade headquarters (more typical in World War I) or directly subordinated to the division commander. By contrast, in a square division, there were typically two brigades of two regiments. Other structures are possible, such as a pentomic division, where the division commander controls five maneuver elements, which was used in the United States Army in the late 1950s, with the regiments replaced by combined arms battlegroups. Imperial Japanese Army and National Revolutionary Army Divisions were organized as square divisions prior to 1938 when they began to form triangular divisions during the Second Sino-Japanese War. Most European armies reorganized their divisions as triangular divisions during World War I, and retained that structure since. Many European armies now place greater emphasis on the brigade and in some cases, such as the Portuguese and the Belgian armies, have eliminated the division entirely as a tactical unit. United States Army divisions were square divisions until the beginning of World War II; reorganization as triangular divisions first occurred in late 1939, lasting through early 1942. During that war, infantry divisions were typically triangular, with the division controlling three infantry regiments. Armored divisions were also triangular, but typically organized into combined arms "combat commands" (denoted Combat Command A, Combat Command B, and Combat Command Reserve). After World War II, this structure was retained until the "Pentomic Era" described above. In the 1960s, United States Army divisions were reorganized as triangular divisions, but with the division controlling three combined arms brigades. Combined arms doctrine has all but eliminated regimental purpose, and regiments generally exist only as traditional designations.