A light machine gun (LMG) is a machine gun designed to be employed by an individual soldier, with or without an assistant, as an infantry support weapon. Light machine guns are often used as squad automatic weapons.
Modern light machine guns often fire smaller-caliber cartridges than medium machine guns, and are usually lighter and more compact. Some LMGs, such as the Russian RPK, are modifications of existing assault rifle designs and designed to share the same ammunition. Adaptations to the original rifle generally include a larger magazine, a heavier barrel to resist overheating, a more robust mechanism to support sustained fire and a bipod.
A light machine gun is also defined by its usage as well as its specifications: some machine guns - notably general-purpose machine guns - may be deployed either as a light machine gun or a medium machine gun. Deployed on a tripod and used for sustained-fire it is a medium machine gun; if deployed with a bipod with the operator in prone position and firing short bursts it is a light machine gun.
Light machine guns are also designed to be fired from the hip or on the move as a form of suppressive fire intended to pin down the enemy. Marching fire is a specific tactic that relies on this capability.
Many light machine guns (such as the Bren gun or the M1918 Browning Automatic Rifle) were magazine-fed. Others, such as the MG 34, could be fed either from a belt or from a magazine. Modern light machine guns are designed to fire more rounds of a smaller caliber and, as such, tend to be belt-fed from a detachable box magazine, some such as the FN Minimi will also accept rifle magazine feeding as an auxiliary measure when belted ammunition has been exhausted.
Light machine guns were first introduced in World War I to boost the firepower of advancing infantry. By the end of World War II, light machine guns were usually being issued on a scale of one per fire team or squad, and the modern infantry squad had emerged with tactics that were built around the use of the LMG to provide suppressive fire.
The following were either exclusively light machine guns, had a light machine gun variant or were employed in the light machine gun role with certain adaptations.