Discussion

Shortly after the United States' entry into World War II, the Marine Rifle Companies were in a state of flux. The Marines had just adopted a new organization,  the D-Series, in March 1941. After Pearl Harbor, Marines issued 2 changes to their tables, one in January 1942 and one in July 1942. As the Marines were hastily mobilizing while simultaneously applying these changes, regiments would have went ashore on Guadalcanal with a hodge-podge of various D-series TO&E versions with varying weaponry (including older WWI-era weaponry and emergency submachine guns), strengths and much of the regiment's motorized assets being left behind.

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At this time the Rifle Company consisted of 1 Company Headquarters, 3 Rifle Platoons and 1 Weapons Platoon. The Infantry Battalion would also have enough Navy Hospital Corpsmen (medics) from its Medical Section to provide 3 per rifle company. The organization as discussed here was effective from March 1941 to April 1943 when it was replaced with the E-Series organization.

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The Company Headquarters consisted of 2 Officers and 26 Enlisted men. The company overall was led by the Company Commander who ideally ranked as Captain, but was sometimes a Lieutenant. A Lieutenant acted as the company's Executive Officer (Second-in-Charge) who handled much of the administrative, rear-echelon workload, while the company First Sergeant was the company's senior enlisted man. A Gunnery Sergeant was added to the Company HQ as well, responsible for ordnance and logistics. Otherwise there was a contingent of rear echelon support personnel. The 7 Other Duty Marines (9 after January 1942) in the Company Headquarters were essentially Riflemen that could be used as replacements as well as mess personnel (the billet was renamed to supernumerary for mess duty in May 1945).

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The Company HQ received a 1/4-ton Jeep in January 1942 which was used mostly for helping to carry 60mm mortar rounds for the Weapons Platoon. Before January 1942, the Infantry Battalion had no motorization whatsoever. Each Company HQ was also authorized 3 anti-tank weapons for local self-defense, although neither of these solutions were issued. From January to July 1942, the company was authorized 3 .60 caliber anti-tank rifles, which were upgraded to 3 M1 Bazookas in July 1942.

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The Weapons Platoon consisted of 1 Platoon HQ, 1 Mortar Section and 1 Light Machine Gun Section. The Platoon HQ was 4 men strong, with a Platoon Commander (Lieutenant), Platoon Sergeant (Platoon Sergeant, equivalent to a Staff Sergeant outside of the infantry) and 2 Messengers (Private). Meanwhile, each of the Sections was led by a Section Leader of the rank of Sergeant and armed with an M1911A1 Pistol and further subdivided into 2 Squads each. The Mortar Squads each served a 60mm M2 mortar and consisted of 1 Squad Leader (Corporal), 1 Gunner (Private), 1 Assistant Gunner (Private) and 2 Ammo Bearers (Private). The Squad Leader was armed with submachine gun (one of the few in the company to have been authorized one as early as March 1941). The Light Machine Gun Squads each served an M1919A4 machine gun from a tripod and consisted of 1 Squad Leader (Corporal), 1 Gunner (Private), 1 Assistant Gunner (Private), and 3 Ammo Bearers. Like in the Mortar Squad, the Squad Leader was armed with a submachine gun. In practice, both the Mortar Section and Light Machine Gun Section were often broken up, with 1 of each squad being detailed out directly to a Rifle Platoon. This differed from Army doctrine of keeping them together, generally speaking. This was most likely due to the unique environment of the Pacific Theatre, where the confines of the jungle forced platoons to take a greater role in fire and maneuver than higher echelons (this also accounted for the Marines' more rapid development and refinement of small unit tactics while the Army's small units stayed the same practically speaking throughout the war). 

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The company's 3 Rifle Platoons consisted of 1 Platoon HQ, 3 Rifle Squads and 1 Automatic Rifle Squad. The Rifle Platoon overall was led by the Platoon Commander (Lieutenant) who was assisted by a Platoon Sergeant (ranked Platoon Sergeant, equivalent to a Staff Sergeant in other trades). The Platoon HQ also contained a Platoon Guide (essentially an assistant Platoon Sergeant, named after their traditional role in bearing the platoon's guide-on in formation), 3 Messengers (allowing the Platoon Commander to send one out per squad simultaneously) and 1 Supply Marine. The Platoon HQ also had 1 spare M1918A2 BAR automatic rifle that could be used for defensive operations, possibly to reinforce a Rifle Squad.

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The Rifle Squad consisted of 9 enlisted personnel. It was led by a Squad Leader of the rank Corporal who was meant to be armed with a submachine gun after July 1942, having been armed with a rifle before hand. If they were to receive a submachine gun, this would most likely have been an M50 Reising, which was procured by the Navy and Marines to supplement small stocks of Thompson submachine guns until the M1 Carbine became more available. The M1928 and M1928A1 Thompson were also used, but in smaller numbers. However, because the TO&E change that authorized submachine guns to Squad Leaders came down fairly close to the Marines' deployment to Guadalcanal, many Squad Leaders likely went without them. The squad further consisted of 1 BAR Man armed with an M1918A2 BAR (although the M1918 and M1918A1 were used in smaller numbers), 1 Grenadier armed with an M1903 Springfield and VB Mk. III or M1 Grenade Launcher, and 6 Riflemen armed with M1903s.

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Although officially authorized the semi-automatic M1 Garand Rifle as of July 1942, the Marines went ashore on Guadalcanal in late 1942 fighting principally with the M1903 Springfield bolt-action rifle. Even so, some units like the 3rd Marine Defense Battalion (a rear echelon guard unit) had a significant supply of the new semi-automatic rifle. This mostly came down to the way the Marine Corps distributed their M1 Rifles when they first acquired them. Although they had been cleared for amphibious operations use in 1940 (there had been fears that the M1 Garand would be less reliable than the M1903 in these environments, which turned out to not be true). In addition to 1940 probably being too late to get sufficient numbers of M1s procured, the Marines did not start by arming their frontline infantry units with the M1. They started with stateside guard units and worked their way down the line to ship detachments and overseas guard units. Back when rifles were personal issue and Marines would be issued the rifle during recruit training which they would then take to their unit, there are photos of Marine recruit platoons armed with a mix of M1 and M1903 Rifles. The men with M1s were bound for rear echelon units while the M1903-armed men were bound for the infantry. In fact the order would not come down to start issuing the M1 Garand to all infantry units until the summer of 1942, but this would be too late for units destined for Guadalcanal. It would not be until early to mid-1943 that Marine units, rebuilding for late 1943 operations, would get the M1 Garand.

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The Automatic Rifle Squad consisted of 8 enlisted personnel and was decidedly offensive in nature. It was led by a Squad Leader of the rank Corporal who was armed with a submachine gun, although unlike the Rifle Squad Leaders they had been authorized submachine guns as early as March 1941. The squad had 2 BAR Men with M1918A2 BARs with 5 supporting Riflemen. This was very similar to what the U.S. Army was running as of October 1940, but this was dropped in April 1942 when the Army's BARs were re-integrated into the Rifle Squads.

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