W54 in the context of "Special Atomic Demolition Munition"

A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either nuclear fission (fission or atomic bomb) or a combination of fission and nuclear fusion reactions (thermonuclear weapon), producing a nuclear explosion. Both bomb types release large quantities of energy from relatively small amounts of matter.

Nuclear weapons have had yields between 10 tons (the W54) and 50 megatons for the Tsar Bomba (see TNT equivalent). Yields in the low kilotons can devastate cities. A thermonuclear weapon weighing as little as 600 pounds (270 kg) can release energy equal to more than 1.2 megatons of TNT (5.0 PJ). Apart from the blast, effects of nuclear weapons include extreme heat and ionizing radiation, firestorms, radioactive nuclear fallout, an electromagnetic pulse, and a radar blackout.

The M28 or M29 Davy Crockett Weapon System was a tactical nuclear recoilless smoothbore gun for firing the M388 nuclear projectile, armed with the W54 nuclear warhead, that was deployed by the United States during the Cold War. It was the first project assigned to the United States Army Weapon Command in Rock Island, Illinois. It remains one of the smallest nuclear weapon systems ever built, incorporating a warhead with yields of 10 to 20 tons of TNT (42 to 84 GJ). It is named after American folk hero, soldier, and congressman Davy Crockett.

A tactical nuclear weapon (TNW) or non-strategic nuclear weapon (NSNW) is a nuclear weapon that is designed to be used on a battlefield in military situations, mostly with friendly forces in proximity and perhaps even on contested friendly territory. Generally smaller in explosive power, they are defined in contrast to strategic nuclear weapons, which are designed mostly to be targeted at the enemy interior far away from the war front against military bases, cities, towns, arms industries, and other hardened or larger-area targets to damage the enemy's ability to wage war. No tactical nuclear weapons have ever been used in combat.