There are two generally recognized classes of weapons identified as heavy machine guns. The first are weapons from World War I identified as "heavy" due to the weight and cumbersomeness of the weapons themselves, which prevents infantrymen from transporting on foot. The second are large-caliber (12.7x99mm, 12.7×108mm, 14.5×114mm, or larger) machine guns, pioneered by John Browning with the M2 machine gun, designed to provide increased effective range, penetration and destructive power against covers, vehicles, aircraft and light buildings/fortifications beyond the standard-caliber rifle cartridges used in battle rifles and medium or general-purpose machine guns, or the intermediate cartridges used in assault rifles, light machine guns and squad automatic weapons, but also have heavy recoils during operation.