Mk 2 American Anti-Personnel 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. The Mk 2 was replaced by the M26-series (M26/M61/M57) and later M33 series (M33/M67). It was phased out gradually in service beginning with the Korean War. Due to the tremendous quantity manufactured during World War II, it was in limited standard issue with the US Army and US Marine Corps throughout the 1950s and 1960s. The U.S. Navy was one of the last users when it was discontinued in 1969. The Mk 2 grenade replaced the failed Mk 1 grenade used by the U.S. military during World War I. 44 million were ordered and more than 21 million were completed (it was possible to convert Mk 1 grenade bodies to the Mk 2 configuration) before the war ended, but few reached American troops overseas. It was formally standardized in 1920. The Mk 2, like the Mk 1, was manufactured of cast iron with a grooved surface divided into 40 knobs in 5 rows of 8 columns. This was to enhance fragmentation (in practice, it was found that the grooves did not enhance fragmentation as much as desired and provide a better grip when handling and throwing the grenade. The grooves and knobs gave it the appearance of a pineapple, and are the origin of that nickname. It was also commonly referred to as a "frag" grenade, in contrast to other types of grenades such as the Mk 3 grenade concussion grenade.