M3 trench knife
The M3 trench knife, or M3 fighting knife, was an American combat knife first issued in March 1943. It was designed to be cheap and quick to produce, using minimal strategic metals and simple manufacturing, while delivering a capable close-quarters weapon. The blade is 6.75 inches long with a spear-point tip and a 3.5-inch sharpened secondary edge. Made of carbon steel, the blade was finished either blued or parkerized.
The grip originally used grooved leather, but later models used stacked leather washers turned on a lathe, polished, and lacquered. The knife’s crossguard has an angular bend to provide a thumb rest. The initial sheath was a stitched and riveted leather M6 with a protective steel tip to prevent puncturing the sheath, plus a rawhide thong to tie the knife to the leg for running. Paratroopers often wore the knife on their boot for emergency use. The M6 sheath was quickly replaced by the M8, and later the M8A1, which uses a resin-impregnated cotton canvas body with a steel throat and olive drab finish. The M8 sometimes lacked the wire hook, which the M8A1 later added; some earlier M8 scabbards were fitted with the hook. Throats are stamped with US M8 or US M8A1 and maker initials. The M8A1 later received an extended tab on the web hanger to allow clearance for the M5 bayonet handle. This sheath design fits post-war U.S. bayonets as well (M4, M5, M6, and M7).
The M3 was developed to replace the World War I Mark I trench knife and to conserve metals. It was evaluated in December 1942 against the KA-BAR and, because of its lower production cost, the M3 was approved for quantity production. Although it was not a dual-use tool like the KA-BAR, the M3 was intended mainly for soldiers who did not have a bayonet, with airborne troops and Army Rangers receiving priority at the start.
The M3 entered wide service in March 1943 and was issued to various groups as production continued through 1943 and 1944, including Army Air Corps crew and soldiers armed with M1 carbines or submachine guns. In 1944 it began to replace the Fairbairn–Sykes fighting knife and the OSS dagger in U.S. service. When the Army developed a carbine bayonet, the M3 blade design and grip were used to create the M4 bayonet for the M1 carbine, adding a bayonet ring and a locking mechanism. The M4 was added to official inventories in June 1944, and the M3 was declared a limited standard item, with supply continuing until exhausted.
Production of the M3 ended in August 1944 after about 2,590,247 knives were made. The blade design continued in later bayonets (M4, M5, M6, M7). While praised for balance and construction, the M3 was not universally loved as a close-quarters fighting knife; its long, narrow blade favored thrusting over cutting, and soldiers found the edge difficult to maintain in the field. Some used it for utility tasks, like opening crates, which led to blade failures, and the partially sharpened false edge plus an unsharpened spine limited backhand slashing.
This page was last edited on 2 February 2026, at 10:16 (CET).