bigpigeon.us webpage WWII > WWII Ground Forces, updated by RAC 10 Jun 2022.
The basic organizational structure of US ground forces during WWII, from largest to smallest units, was as follows:
Army Group > Army > Corps > Division > Regiment > Battalion > Company > Platoon > Squad.
Notes on the above:
US Army Divisions - there were six kinds:
Some will find the following source useful: Referring to this source, regarding WW II infantry divisions:
Various ad-hoc temporary organizations smaller than a division but generally larger that a battalion included:
Many company, battalion, or regimental combat units were independent in that they were not permanently assigned to a division, but were managed at the corps or army level.
A potentially useful document:
Army infantry division organization.
Ignoring the headquarters company, each army infantry division contained the following organic (i.e., permanent) units:
Using the above, you may be able to do some web research:
1 - Suppose you know your grandfather served in the ETO, you know his unit (e.g., 571st Signal Co.), but you don't know his division:
In WWII, the core of each Army infantry division (and each Marine Corps division) consisted of three infantry regiments, each regiment having three infantry battalions, and each battalion having four infantry companies:
Some will find the following links useful:
Army and Marine Corps divisional artillery organization.
Army Infantry:
Links to additional Army and Army Air Force reports:
The basic organizational structure of US ground forces during WWII, from largest to smallest units, was as follows:
Army Group > Army > Corps > Division > Regiment > Battalion > Company > Platoon > Squad.
Notes on the above:
- Regimental-sized and larger units included smaller units from many Arms and Service branches, the Arms branches being Infantry, Artillery, Armor, and (sometimes at least) Engineers.
- The Marine Corps fielded six infantry divisions, had a corps as the highest organizational level, and fought only in the War with Japan.
- A non-infantry platoon was sometimes organized into sections rather than squads.
US Army Divisions - there were six kinds:
- Infantry - All of the numerous infantry divisions had at their core three infantry regiments.
- Light Armored - contained three armored infantry battalions, three tank battalions, and three armored artillery battalions. All light armored divisions served in the War with Germany.
- Airborne - core consisted of two parachute infantry regiments and two glider infantry regiments.
- Heavy Armored - only the 2nd and 3rd Armored Divisions, both of which served in the ETO.
- Cavalry - only the 1st Cavalry Division, which served in the Southwest Pacific.
- Mountain - only the 10th Mountain Division, which served in Italy.
Some will find the following source useful: Referring to this source, regarding WW II infantry divisions:
- The 1st - 9th, 12th, 24th, 25th, and 42nd were Regular Army divisions.
- The 23rd, 26th - 38th, 40th, 41st, and 43rd - 45th were National Guard divisions.
- The 63rd, 65th, 66th, 69th-71st, 75th-81st, 83rd-100th, 102nd-104th, and 106th were Reserve divisions.
- The 12th Division, which included Filipinos serving in the USS Army, was earlier known as the Philippines Division and was lost in the Fall of the Philippines in 1942.
- The 23rd Division was earlier known as the Americal Division and was organized in New Caledonia in 1942 from surplus National Guard units.
- The 34th Division consisted of National Guard units from Iowa, Minnesota, Nebraska and the Dakotas.
- The 92nd and 93rd Divisions were segregated; i.e. enlisted men were black and higher-ranking officers were white.
Various ad-hoc temporary organizations smaller than a division but generally larger that a battalion included:
- Regimental Combat Teams were built around an infantry regiment and supporting units. The best-known was the Japanese-American 442nd Regimental Combat Team, which fought in Italy and France.
- Combat Commands usually consisted of a tank battalion, an infantry battalion, and an artillery battalion taken from an armored division. They were heavily used both in the Mediterranean and European Theaters.
Many company, battalion, or regimental combat units were independent in that they were not permanently assigned to a division, but were managed at the corps or army level.
- An example was the 112th Cavalry Regiment of the Texas National Guard which served in the Southwest Pacific. My daughter's father-in-law, Lloyd Joyce, served in this unit.
- As the need arose, the army or corps commander would assign independent tank, tank destroyer, artillery, antiaircraft artillery, or engineer units to a division. These units, most often of battalion size, often served with a division for extended periods.
A potentially useful document:
- https://history.army.mil/documents/ETO-OB/ETOOB-TOC.htm - Order of Battle (organizational information) for ETO divisions. As noted above, army divisions had numerous units attached to them at various times. This document lists all such attachments. It also lists division command posts, which can be used to chart the course of a division across western Europe.
- https://history.army.mil/documents/ETO-OB/IDs-ETO.htm - Organic Composition of Infantry Divisions (a section of the above document).
Army infantry division organization.
Ignoring the headquarters company, each army infantry division contained the following organic (i.e., permanent) units:
- three infantry regiments.
- four field artillery battalions.
- one each of a signal, quartermaster, and ordnance company.
- a reconnaissance troop (troops were company-sized).
- an engineer combat battalion.
- a medical battalion.
Using the above, you may be able to do some web research:
1 - Suppose you know your grandfather served in the ETO, you know his unit (e.g., 571st Signal Co.), but you don't know his division:
- Enter https://history.army.mil/documents/ETO-OB/IDs-ETO.htm
- Search the webpage for 571.
- You should find that the 571st Signal Co. was in the 71st Infantry Division.
- Enter https://history.army.mil/documents/ETO-OB/ETOOB-TOC.htm
- Click on the 4th Infantry Division chapter.
- Scan through the Attachments section.
- Sure enough, the 70th Tank Bn. was attached to the 4th Infantry Division from 10 July 1944 to 10 March 1945.
In WWII, the core of each Army infantry division (and each Marine Corps division) consisted of three infantry regiments, each regiment having three infantry battalions, and each battalion having four infantry companies:
- First Battalion: Co. A (rifle), Co. B (rifle), Co. C (rifle), Co. D (heavy weapons)
- Second Battalion: Co. E (rifle), Co. F (rifle), Co. G (rifle), Co. H (heavy weapons)
- Third Battalion: Co. I (rifle), Co. K (rifle), Co. L (rifle), Co. M (heavy weapons)
Some will find the following links useful:
- The February 1944 TO&E (Table of Organization and Equipment) for an Army infantry company - http://www.militaryresearch.org/7-17%2026Feb44.pdf.
- A summary of Marine Corps divisional combat experience at https://www.usmcu.edu/Research/Marine-Corps-History-Division/Information-for-Units/Battle-Honors-of-the-Six-Marine-Divisions-in-WWII/.
Army and Marine Corps divisional artillery organization.
Army Infantry:
- Three battalions of 105-mm howitzers and one of 155-mm howitzers. Infantry divisional artillery was towed rather than self-propelled.
- In addition, each infantry regiment had a 105-mm howitzer cannon company and a 57-mm gun antitank company.
- Three battalions of self-propelled 105-mm howitzers mounted on the M7 Priest motor carriage.
- Battalions generally equipped with 75-mm pack howitzers.
- In WW II airborne operations, heavier equipment landed in gliders.
- Four or five artillery battalions, organized into a 4th regiment (e.g., the 22nd Marine Regiment (artillery) was the 4th regiment in the 1st Marine Division).
- Early in WW II, a marine division’s artillery regiment had three battalions of 75-mm pack howitzers and one of 105-mm howitzers.
- As the war progressed, more 105-mm howitzers were added and the number of pack howitzers was reduced.
Links to additional Army and Army Air Force reports:
- In WWII, the Iowa National Guard was a component of the 34th Infantry Division. The 168th Infantry Regiment in WW II has more information, although it is currently incomplete.
- ETO Ground Forces Outline - high-level ETO Army Group/Army/Corps organization in early February 1945.
Sources for the WW II Divisions webpage:
- The webpage header image depicts a full-strength WW II Army infantry division rifle squad and is courtesy of https://www.battleorder.org.