During the war, America lacked a fragmentation grenade of their own production. So in 1917, they came up with the MK 1. This was a fragmentation(32 serrations) grenade that was promised to be simple yet foolproof. However it proved to be difficult to use in the war, often ending up being thrown without being lit, resulting in the grenade being thrown back by the enemies, this time properly lit. Production was almost immediately stopped.