Marines training with a 60mm mortar

Adopted on 28 March 1941, the D-series tables of organization remained in force for a little more than two years. During that time the Marine Corps made two sets of changes to them. The first of these bore the date of 10 January 1942. The second received official blessing on 1 July 1942.

Thanks to these changes, the authorized strength of the Marine infantry regiment increased from 2,996 to 3,168. In other words, the ideal Marine infantry regiment of 1 July 1942 was some five percent larger than than its full-strength counterpart of 28 March 1941.

Number of men rated by the battalions (forest green), headquarters and service company (khaki), and weapons company (cordovan) of a Marine infantry regiment

Most of the growth within the regiment (135 of the 172 officers and men added during this period) took place within the three infantry battalions. Of the rest, nearly all of the increase (36 out of 37) occurred within the regimental headquarters and service company, and, in particular, the regimental communications platoon.

Authorized strength of each of the major elements of the Marine infantry regiment (28 March 1941/1 July 1942)

Within each infantry battalion, the number of Marines in each rifle company grew slightly, the number of Marines in the weapons company grew somewhat, and the number of Marines in the headquarters company grew considerably. (The headquarters company of each infantry battalion also provided a home for two medical officers and twenty hospital corpsmen of the US Navy. This number, however, did not change during the two year reign of the D-series tables of organization.)

Of the twenty Marines added to the headquarters company of each infantry battalion, sixteen served within the communications platoon. Of these, twelve operated radio sets, three drove jeeps, and one strung wire.

Authorized Strength of each of the major elements of the Marine infantry battalion (28 March 1941/1 July 1942)

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