Classic Combat Knives: The Mk III Trench Knife

Author holding M3 Trench Knife in modified Applegate grip

The close-quarter trench fighting of World War I brought the combat knife back into prominence among a soldier’s weapons.  The immediate answer were trench knives equipped with heavy knuckle guards. These combined the striking power of brass knuckles with the stabbing force of a dagger. Some had triangular thrusting blades. Others were equipped with a double-edged dagger blade. They were good for the close quarters of a trench brawl, but little else.

Between the wars, both the Army and Marine Corps sought a reliable combat knife. The most immediate response was the bayonet, whic h coud lalso serve as a knife. The bayonet of World War II was a cut-down M1907 bayonet. It was made of good steel and was a manageable size. However, both services needed a knife for those not equipped with an M1 rifle.

The Army came up with the M3 trench knife. It had a single blade wit ha thick spine and false edge. The handle was made of tightly-compressed leather washers. It had a small crossguard to prevent the hand from running up onto the blade when thrusting. The M3 blade was later used on rifle bayonets from the M1 to M7 models. (The M1 rifle, M1 carbine, M14 rifle and M16).

M3 Trench Knife

The M3 was mostly a thrusting weapon. It could punch through heavy clothing. It was not a very good camp knife. The M3 Trench Knives were sharpened.

The M3 blade in bayonets was replaced by a Bowie-type blade in the 1990s. It is more practical as a camp knife. Remaining M7s were sold to allies using the M16 or put on the civilian market for collectors. A few knife manufacturers still sell M3s and the M7 Bayonets, mostly for collectors.

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The M3 style blade fit the style of knife fighting devised by Col. Rex Applegate for the O.S.S.  Applegate claimed that his staff examined many styles of knife fighting. You can see the influence of W.E. Fairbairn in his work. As late as 1992, Applegate’s method was still taught to the US Army.  Even the grip is right out of Applegate’s work.

Apprlegate grip, from 1971 Army manual Combatives FM 21-150

Applegate Stance, from Army FM 21-150 (1971)

Applegate stance, from 19992 Army Combatives manual

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My experience with this style blade is mostly via the M7 bayonet. These blades were not sharpened. In fact ,we were forbidden to sharpen them. I remember one occasion where we were probing in wet sand. A couple of times, we had to remove a “land mine.” (This was training.) The edges of the blades curled ever so much. The steel was too soft. That is a problem with the M7 and other military knives made in massive numbers.. They are tempered in batches. Quality of the tempering varies, so that one may encounter examples that are too soft or too brittle. Keep in mind that these knives / bayonets are also made by a variety of manufacturers. Quality control and methods may vary from one plant to another.

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M3 Trench Knife, M7 Bayonet, Modern version of M3

Pictured here: M3 Trench knife, M7 Bayonet, modern knife based on the M3. The leather-ring handle offers a secure grip. All three have pommels that keep the hand from slipping off. *

*You cannot count on ideal conditions when working with a knife. Wet hands, thick gloves and other things can make adversely affect your grip. That is why I like a pommel that keeps my hand from slipping off the end.

A crossguard’s main purpose is to keep your hand from sliding onto the blade. Thrusting and pushing are best avoided on knives that have no guard. One group who often run afoul of their own knives are criminals. Many a criminal leaves his blood on the blade. Finger-grips are no substitute for the safety of a crossguard.