M3 trench knife

The M3 trench knife or M3 fighting knife was an American military combat knife first issued in March 1943. The M3 was originally designated for issue to soldiers, not otherwise equipped with a bayonet. However, it was particularly designed for use by forces in need of a close combat knife, such as Airborne Units and Army Rangers, so these units received priority for the M3 at the start of production. As more M3 knives became available in 1943 and 1944, the knife was issued to other soldiers such as Army Air Corps crewmen and soldiers not otherwise equipped with a bayonet, including soldiers issued the M1 carbine or a submachine gun such as the M3 submachine gun "grease gun".

The M3 trench knife was developed as a replacement for the World War I-era U.S. Mark I trench knife, primarily to conserve strategic metal resources. The M3 would also replace the Fairbairn–Sykes fighting knife or OSS dagger in U.S. service in 1944. In August of 1944, the M3 fighting knife evolved into the M4 bayonet for the M1 carbine with the addition of a bayonet ring to the hilt and a locking mechanism in the pommel.