US Army Infantry battalions during World War II each had a heavy machine gun platoon assigned to the battalion’s weapon company. This platoon had four M1917 Browning .30 machine guns. While rifle companies (and, toward the end of the war, rifle platoons) had two M1919 .30cal machine guns, those were air cooled, and had limited rates of fire and ammunition supply. Because the M1917 was water cooled, it could sustain a much higher rate of fire for a longer time, and each gun team could often use their assigned jeep and trailer to move considerable supplies of ammunition.
Like almost everything else John Moses Browning designed, the M1917 was a splendid weapon. It was rugged, simple, reliable and extremely effective. It served as the US Army’s primary heavy machine gun from World War I through the end of the Korean War. Its design was developed into the air-cooled M1919 and eventually evolved to form the basis of the M2 .50cal machine gun, which serves to this day in our Army.
Today we tend to think of the heavy machine gun in terms of the M2 .50cal, but the term of art then meant more than simply one of large caliber. Heavy meant that it was a support weapon, generally firing from semi-fixed positions while rifle elements maneuvered. The light machine guns would maneuver with their companies during the attack as need. Heavy machine gun platoons would displace as the supported units outran the range of their supporting fire, but not generally actually maneuver.
For you non-Infantry types out there, almost all the tactics described here are still applicable, even if the heavy machine gun is no longer in use. For instance, the primary, alternate, and supplementary positions are applicable to light machine guns, tanks or Bradleys, or any other supporting weapon.
By the way, who remembers filling out one of these?