Mk 2 Fragmentation Grenade

The **Mk 2 grenade** (initially known as the **Mk II**) is a fragmentation type anti-personnel hand grenade introduced by the U.S. armed forces in 1918. It was the standard issue anti-personnel grenade used during World War II and in later conflicts, including the Vietnam War. Replacing the failed Mk 1 grenade of 1917, it was standardized in 1920 as the Mk II, and redesignated the Mk 2 on April 2, 1945. It is also used by the Japan Self Defense Forces (JSDF).

## Description

Generally, a grenade consists of an explosive charge, a detonating mechanism, and firing pin inside the grenade to trigger the detonating mechanism. Once the soldier throws the grenade, the safety lever releases, the striker throws the safety lever away from the grenade body as it rotates to detonate the primer. The primer explodes and ignites the fuze (sometimes called the delay element). The fuze burns down to the detonator, which explodes the main charge.

There are several types of grenades like the fragmentation (frag), high explosive (HE) concussion and smoke grenades.

### Types of Grenades

#### **Fragmentation (Defensive)**

Fragmentation grenades are common in armies. They are weapons that are designed to disperse lethal fragments on detonation, in order to do damage in as wide an area as possible. The body is generally made of a hard synthetic material or steel, which will provide some fragmentation as shards and splinters, though in modern grenades a pre-formed fragmentation matrix is often used. The pre-formed fragmentation may be spherical, cuboid, wire or notched wire. Most AP grenades are designed to detonate either after a time delay or on impact.

#### **High Explosive (Offensive)**

The offensive or concussion (high explosive) grenade is an anti-personnel device that is designed to damage, daze or otherwise stun its target with its explosive power. Compared to fragmentation grenades, the explosive filler is usually of a greater weight and volume, and the case is much thinner – the US MK3A2 concussion grenade, for example, has a body of fiber (similar to the packing container for the fragmentation grenade).

These grenades are usually classed as offensive weapons because the small effective casualty radius is much less than the distance it can be thrown. The concussion effect, rather than any expelled fragments, is the effective killer. In the case of the US Mk3A2, the casualty radius is published as 2 m (6 ft 7 in) in *open* areas, but fragments and bits of fuze may be projected as far as 200 m (660 ft) from the detonation point.

They have also been used as depth charges (underwater explosives) around boats and underwater targets; some like the US Mk 40 concussion grenade are designed for use against enemy divers and frogmen. Underwater explosions kill or otherwise incapacitate the target by creating a lethal shock wave underwater.

#### **Anti-Tank**

A range of hand-thrown grenades has been designed for use against heavily armored vehicles. With correct emplacements, the AT Grenade can cripple tank movements by destroying the thread or punch through its armor.

## Service History

The Mk. 2 was used during Operation Momotarou by the JGSDF Advanced Platoon. It was thrown against the Red Ogre but it had no effect on the said monster.