When America entered World War 1 in 1917, it lacked much in the way of modern war weapons. Army forces were delivered various foreign goods for which to move forward and make war with. Among these implements was the fragmentation hand grenade. The US military procured both the British "Mills Bomb" and French F1 series and, within time, decided to was prudent to develop and indigenous American grenade. To formulate their new grenade, the Americans followed the French F1 design and eventually outputted the Mk 1, a time-fused hand grenade showcasing the then-standard "pineapple" exterior.
However, once in practice, the Mk 1 left much to be desired. It proved quite cumbersome in the field by way of its complicated ignition system which often times saw the grenades being thrown without being armed. The Mk 1proved so poor that a new initiative was begun to produce a successor. As such, the Mk 1 was discontinued and declared obsolete even before the war had concluded in November of 1918. By this time, the improved Mk 2 production model was in production, bringing an end to the forgettable chapter that was the Mk 1.
The Mk 2 went on to see much more major successes in the field of play. It saw service in 1918 but was not standardized in the American inventory until 1920. By World War 2, the Mk 2 was the standard fragmentation grenade of American forces and saw extensive use in the conflict. Its widespread availability made sure that the type would see subsequent combat action in both the Korean and Vietnam wars to come. The Mk 2 was eventually replaced in the 1960s by the M26 series - officially doing away with the "pineapple" exterior utilized by many hand grenade weapons for decades prior. The smooth-sided nature of the M26 led to it being affectionately named as the "Lemon Grenade".
The M26 series was a rather basic instrument of war. The body was made up of a smooth casing, divided by a single rib along the circumference with a short flat bottom, the latter allowing the grenade to sit atop level surfaces. The top was capped by the curved lever (also known as the "spoon"" which was held in place by a safety pin attached to a rather non-descript ring. The grenade weighed in at 454g and featured a length of 99mm and diameter of 57mm. The series was filled with 164g of Composition B filling and detonated by way of a timed friction fuse. The blast radius was designed to be compacted within a 15 meter radius, fragments being spread out evenly, and yielded a smokeless fuse mechanism (Mk 2 grenades had a nasty habit of giving up the users position and intention).
Operation of the grenade was basic - with the use needing to pull the safety pin which freed the lever. The user could then throw the grenade against the target area. When thrown, the lever was sprung free from the grenade, activating the firing pin which, in turn, struck the primer. The sequence then initiated the timed fuse (about 4 to 5 seconds long) which ultimately led to its detonation. Upon detonation, the casing of the grenade was shattered and thrown about the target area, creating the necessary fragments and causing maximum damage to the area. If the shards did not maim or outright kill the enemy, the explosion served as a psychological effect. The use could pull the pin of his M26 and still keep a sure hold of the lever - for so long as the lever was intact against the grenade body, the grenade's fuse was not activated.
The M26 entered military service in the 1950s, being used primarily by the United States as well as allies Australia, Canada (M61), the United Kingdom (L2), Israel (M26A2), Portugal (M312), South Africa and South Vietnam.
The M26 was further evolved into the M26A1 and M26A2 production forms, the former having fragmentation serrations added against the explosive filling content while the latter was revised to use impact fuses. Another key iteration of the M26 family became the M61 which was based on the M26A1 production model. The M61 was developed after jungle warfare in Vietnam had shown the M26 to be susceptible to snagging, which led to unintended detonations. As such, an extra safety clip - otherwise known as the "jungle clip" - was added to the M26's design. The user was then required to pull both the original safety ring pin as well as the jungle clip before throwing his grenade. Canadian armed forces also made use of the M61 form but this - as well as the M26 in American service - was replaced by the modernized M67 series (which Canada produces as the C13).