• 
• 

Infantry - Organizational configurations during the 20th Century

The US mobilized sixty-seven infantry divisions in World War II. They were the 1st-9th, 10th Mountain, 24th-38th, 40th-45th, 63rd, 65th, 66th, 69th-71st, 75th-81st, 83rd-91st, 92nd and 93rd Colored, 94th-100th, 102nd-104th, 106th, and Americal Infantry Divisions, 11th, 13th, 17th, 82nd, and 101st Airborne Divisions, and the 1st Cavalry Division, which was dismounted and utilized as infantry. Forty-two of the infantry divisions and four of the airborne divisions served in the ETO and MTO, the remainder served in the PTO.

The first permanent divisional organization in the U. S. Army appeared in World War I. Nine of these infantry divisions continued to exist through the 1920s and 1930s. These were "square" (two two-regiment brigades) organizations which were replaced, after considerable arguments and field tests, by a "triangular" organization of three regiments. By early 1942 the division was organized substantially the way it would be used in battle, with, in addition to its three infantry regiments, four artillery battalions (three twelve-tube 105mm light battalions and one twelve-tube 155mm howitzer medium battalion), a cavalry reconnaissance troop, and division service troops. A major general commanded the division. A brigadier general was assistant division commander and a second brigadier general was division artillery commander. Colonels commanded the infantry regiments and lieutenant colonels the battalions.

Note: Due to mobilization for World War I the army adopted its "square division" organization structure significantly increasing unit sizes from platoon up. In 1917 a fourth platoon was added to the company increasing its size to 256 officers and men, including six officers (a captain as commanding officer, a first lieutenant as executive officer, and two first lieutenants and two second lieutenants as platoon commanders). Enlisted strength became: three senior NCOs (first sergeant, supply sergeant, and mess sergeant), 12 sergeants, 33 corporals (one company clerk and 32 squad leaders with eight per platoon), eight specialists (four cooks and four mechanics), two buglers, 64 privates first class, and 128 privates. Of the 12 sergeants, while eight of them continued to serve as section leaders (with two in each platoon), the four senior ranking sergeants were assigned to a new position in each platoon headquarters as "assistant to platoon commander". This was the forerunner of the modern platoon sergeant slot created in 1943 (originally known in 1940 as the "platoon leader", as the officer was styled as the "platoon commander" until 1943) to provide an experienced senior NCO as an advisor and second-in-command to the officer commanding the platoon.

In mid-1944 (TO&E 7, dated 15 July 1943) the infantry division had 18 M3 105mm infantry howitzers, 36 M2 105mm howitzers, 12 M1 155mm howitzers, 5 half tracks, 13 M8 armored cars, 1,371 motor vehicles, and 10 light observation aircraft. Total personnel strength was 14,253.

The infantry regiment was organized with three battalions, twelve lettered companies (A-M, skipping J), an Infantry Cannon Company (first equipped with two half track-mounted 105mm howitzers and six half track-mounted 75mm howitzers or guns, and later with a towed short-barreled 105mm howitzer), an Antitank (AT) Company (initially with twelve 37mm and later nine 57mm AT guns), and a Service Company. The fourth company in each battalion (D, H, M) were heavy weapons companies with sustained fire heavy machine guns and mortars. The regiment and each battalion also had a H&H Company. The regimental H&H Company included a Intelligence and Reconnaissance Platoon, the battalion H&H company included an Ammunition and Pioneer (A&P, responsible for light engineering duties and for transporting ammunition forward to the line companies) Platoon and an AT Platoon (initially with four 37mm and later with 3 57mm AT guns).

In theory the US infantry regiment of World War II was a powerful, flexible organization and was the core of the infantry division. Unfortunately, poor personnel replacement planning in the early years of the war meant that after a few weeks of combat the regiment was chronically under strength. As an example, on 1 December 1944 the Third Army was under strength in infantrymen by the equivalent of 55 rifle companies. In effect, this meant that on average each of Third Army's infantry divisions were at two-thirds strength in their rifle companies.

After WWII - Vietnam

Sizes of the various units, Brigade, Battalion and Division in Vietnam differed greatly. Most companies operated with a field strength of 80-100 men excluding the 4th Heavy weapons platoon. TOE calls for a total strength of about 160 men. A brigade would include 3 manueauvering battalions, 1 mechanized unit, a squadron of tanks plus 1-2 field artillery batteries plus HHC groups.