The W54 (also known as the Mark 54 or B54) was a tactical nuclear warhead developed by the United States in the late 1950s. The weapon is notable for being the smallest nuclear weapon in both weight and yield to have entered US service. It was a compact implosion device containing plutonium-239 as its fissile material,[1] and in its various versions and mods it had a yield of 10 to 1,000 tons of TNT (42 to 4,184 gigajoules).
The weapon had two distinct versions: a warhead used in the AIM-26 Falcon air-to-air missile and in the Davy Crockett recoilless gun, and another used in the Special Atomic Demolition Munition (SADM) system, along with several mods for each version. The two types are distinct in that much of the design between them was different, to the point that during the development of the SADM it was proposed that it be given its own unique mark designation.
A later development was the W72, which was a rebuilt W54 used with the AGM-62 Walleye guided bomb. The W72 was in service until 1979.