The M1918 Trench Knife was designed as an American answer to the German Mauser Bayonet, (universally used on most models of Mauser rifles in the first world war) which proved exceedingly useful in the trench warfare that WWI was well known for.
Originally a collective concept formulated by the French, in their creation of a long, needle-like stiletto blade aptly named an Poignard-Baïonnette Lebel, the United States defense contractors Henry Disston & Sons took the steps a bit further with the original designs (both the P-B Lebel and the M1917) which were too brittle, and was often found to snap off in certain combat situations, namely between an enemy combatant’s ribs. This was quite obviously problematic. Replacing this design with upgraded sets of the original trademark knuckle guards and spiked brass knuckles, as well as a thicker, sturdier blade of forged steel.
It saw service through four wars, from the First World War, all the way over to early Vietnam. It even saw use on the civilian front, during Mafia Gang wars in the time of American Prohibition. Reproductions are now sold worldwide.