The Marine Division in World War II

The Marine division was a balanced and powerful combat force designed and equipped to carry out any assigned operation. Able to sustain itself for protracted time periods under brutal conditions, the divisional structure was ideally suited to the rugged island campaigns. The basic strength of the Marine division proved itself again and again in the Pacific war.

Marine planners first envisioned a true all-Marine division during the First World War. These ideas never came to fruition for numerous reasons. Nevertheless, the way to the future was clear. The Corps would need to organize its own combat divisions for any future war.

The reality of war on the Western Front showed that regimental or brigade-sized units were simply too small for independent operations. During the 1920s, many officers contributed brilliant work to what sort of role the Marine Corps would play in future wars. Prominent among them was LtCol Pete Ellis, who in 1920 conceptualized the key factors of a future Pacific war against Japan.

The Marine Corps built a resilient foundation for World War II when the Fleet Marine Force was established in 1933. Under this framework, two Marine brigades were organized, one on each coast of the United States. These units became the basis for the first two Marine divisions to be stood up in 1941.

During the fighting on Tarawa in November 1943, a Marine rifleman pauses for a drink of water. USMC Photo

The basic structure of the division remained fairly constant and is so even to the present. The core fighting power was built around three infantry regiments and organic fire support came from an artillery regiment. Armored support came from the divisional tank battalion. The division had its own headquarters, engineer, motor transport, medical, pioneer and service battalions.

As the war progressed, each campaign brought new lessons learned and these were used to adapt and improve the Marine division's organization and structure. As newer and better weaponry became available, these were also deployed into the fleet. During World War II numerous changes were made to the number and type of weapon systems used by the Marine division. The division's organizational structure evolved through four separate phases between 1941-1945. They are as follows:

Marine divisions
28 March 1941
1st & 2nd
D-100 (modified)
10 January &
1 July 1942
1st, 2nd, 3rd
15 April 1943
1st, 2nd, 3rd, 4th
5 May 1944
1st, 2nd, 3rd, 4th, 5th, 6th
4 September 1945
1st, 2nd, 5th, 6th (implemented in January 1945 in 1st, 2nd, & 6th)

Depending on the operation, divisions were often reinforced with support assets from FMFPac, or even from the other services. These attachments might include amphibian tractor, tank, and truck battalions, various types of communications and intelligence units, field hospitals, etc. The divisional size often swelled to over 25,000 men for major operations, especially later in the war. During the war, six Marine divisions served in combat.

The Marine divisions of World War II
Date activated Place activated Nickname Campaigns
1st MarDiv 1Feb41 Guantanamo Bay, Cuba The Old Breed Guadalcanal(*), Cape Gloucester, Peleliu(*), Okinawa(*)
2nd MarDiv 1Feb41 MCB, San Diego The Silent Second Guadalcanal, Tarawa(*), Saipan, Tinian
3rd MarDiv 16Sep42 Camp Elliot, Calif. The Fighting Third Bougainville, Guam, Iwo Jima(*)
4th MarDiv 16Aug43 Camp Pendleton, Calif. The Fighting Fourth Roi-Namur, Saipan(*), Tinian, Iwo Jima(*)
5th MarDiv 21Jan44 Camp Pendleton, Calif. The Spearhead Iwo Jima(*)
6th MarDiv 7Sep44 Guadalcanal The Striking Sixth Okinawa(*)

(*) Each campaign with an asterisk after it indicates the division was awarded the Presidential Unit Citation. The Department of the Navy awarded the PUC to the assault elements of the Vth Amphibious Corps for the Iwo Jima operation. Support elements of the 3rd, 4th, and 5th Marine Divisions received the Navy Unit Commendation.







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