During World War II, the Mark I was issued in 1942 and 1943 to airborne troops, Army Rangers, and Marine Raiders. The Mark I featured a full-tang design with a double-edged blade and a heavy bronze hilt incorporating a guard ostensibly shaped as a "knuckle duster", though the latter was intended to protect the fingers and prevent the knife from being knocked from the hand while in combat rather than for use as a weapon. Reflecting the savagery of hand-to-hand trench warfare, the Mark I's pommel incorporated a so-called 'skull-crusher' cap extension, ostensibly designed to stun or kill an enemy soldier and to provide a secondary weapon in circumstances where the blade was damaged or broken. A special proprietary metal scabbard was issued with the Mark I, capable of accommodating the new knife and its oversized knuckleduster grip handle.