During the Second World War, Marine infantry regiments employed two types of tripod-mounted .30-caliber Browning machine guns. The lighter of the two models, which was often described as the ‘light machine gun’, made use of an air-cooled barrel. The heavier weapon, known as the ‘heavy machine gun’, sported a water jacket.
The number of Marines who devoted their time and trouble to the feeding and firing of these machines guns varied greatly over the course of the war. This figure remained steady in 1942, rose considerably in 1943, and plummeted in 1944. In the last year of the war, however, it returned to a level comparable to the one authorized on the eve of the conflict.
When the number of machine gunners allowed to each infantry regiment is expressed as a percentage of the total number of Marines rated by units of that sort, the overall pattern holds. Nonetheless, when compared to the great increase in the number of Marines allowed to each infantry regiment by the establishments approved on 1 May 1945, the recovery of the last year of the war appears to be less than a fully-fledged return to the status quo ante.
During the first two years of the war, different elements within the infantry regiment employed different types of machine guns. While the machine gunners assigned to rifle companies were armed with air-cooled machine guns, those who served in the weapons companies of infantry battalions used their water-cooled counterparts.
At the start of 1944, however, the abolition of battalion weapons companies deprived the heavier weapons of their crews, leading to a situation in which the lighter machine guns served as the default weapon of all machine gun elements of the infantry regiment. However, rather than resulting in the removal of the water-cooled Brownings from the regiment, the later weapons were placed under the direct control of the officers commanding rifle companies, to be issued in situations where the need for additional automatic fire justified the work needed to move and, especially, feed additional guns.
Source: The information in this article comes from the organizational diagrams created by John Sayen for Battalion: An Organizational Study of United States Infantry. These diagrams, in turn, drew their data from the official tables of organization published by Headquarters US Marine Corps between March of 1941 and May of 1945.
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