Passage: The modern definition refers to a class of large-caliber (generally .50 or 12.7mm) machine guns, pioneered by John Moses Browning with the M2 machine gun.  These weapons are designed to provide increased range, penetration and destructive power against vehicles, buildings, aircraft and light fortifications beyond the standard rifle calibers used in medium or general-purpose machine gun, or the intermediate cartridges used in light machine guns. In this sense, the "heavy" aspect of the weapon refers to its superior power and range over light- and medium-caliber weapons, in addition to its weight. This class of machine gun came into widespread use during World War II, when the M2 was used widely in fortifications, on vehicles and in aircraft by American forces. A similar HMG capacity was later fielded by the Soviets in the form of Vasily Degtyaryov's DShK in 12.7×108mm. The ubiquitous German MG42 general-purpose machine gun, though well-suited against infantry, lacked the M2's anti-fortification and anti-vehicle capability, a fact that was noted and lamented by the Germans. The continued need for a longer-range machine gun with anti-materiel capability to bridge the gap between exclusively anti-infantry weapons and exclusively anti-materiel weapons has led to the widespread adoption and modernization of the class, and most nations' armed forces are equipped with some type of HMG.

Question: When did light machine M2 guns come to use?
World War II,