In the early 1900s, the "rifle grenade" as a viable battlefield weapon began to take form - its first notable use witnessed at the Battle of Port Arthur by the Japanese forces against the Russians. By the time of World War 1 (1914-1918), the French implemented their own variety of rifle grenade on a large scale and found the weapons to offer much value for the investment considering the war had bogged down to Trench Warfare tactics by the end of 1914. With this foundation, the weapon type evolved some throughout the interwar years to become a more potent implement by the time of World War 2 (1939-1945).
Like other global military powers, Britain adopted various rifle grenades and, with its commitment to World War 2 beginning in September of 1939, the race was on to stock the Army inventory with useful tools for the combat infantryman. Development soon began on a new rifle grenade known rather simply as the "No. 68". This weapon represented a basic armor-defeating (HEAT - High-Explosive, Anti-Tank) solution and was developed against the threat of early generation German Panzers. The grenade gave results up to 2 inches of armor protection depending on type of filling used and approach angle of the grenade (90-degrees being ideal).
The No. 68 featured a highly utilitarian design with a flat top and bottom face, a thin neck holding the pin, and a finned tail unit. A grenade discharger "cup" was first attached to the rifle muzzle (mainly the Enfield .303 bolt-action service rifle). The No. k68 grenade was then installed into this apparatus and the pin removed prior to firing. Throughout its service life, the grenade featured a variety of filling elements with early versions carrying RDX and later marks approved with Pentolite and Lyddite fillings. The grenade's detonation was simply through direct impact.
Issuance to British forces began in the middle part of 1940 through the Mark I service model. Circulation soon counted some 10,000 units delivered though this impressive number was still some millions below what the Army was calling for. After some practical use in the field, a spade assembly was developed to assist the firing operation and contend with the rather impressive recoil of the discharging grenade. The improved Mark II grenade appeared during August of 1940 and this was followed in early 1941 by the Mark III and, finally, the Mark IV AT grenade types. The latter marks were primarily seen with Pentolite filling. During 1941 alone some 2.6 million of the grenades were manufactured and this was itself outdone by the 5.3 million that appeared from production in the year following. Beyond their use by Army forces, the No. 68 grenade was delivered to British Home Guard units from 1942 on - the grenade's frontline value having finally run its course.