Fusion device

(PD) Photo: U.S. Department of Energy
IVY MIKE, the first thermonuclear explosion in which part of the explosive yield comes from nuclear fusion.

A fusion device is any assembly of components that can produce an explosion from nuclear fusion. A 'fission bomb' can be dropped from an airplane, or at least transported to a real target. In contrast, the first thermonuclear device, Operation Ivy#IVY MIKE|IVY MIKE, detonated on Bikini Island, was not transportable. A fusion warhead is a device that is sufficiently small and rugged to be used, operationally, as the warhead of a guided missile, artillery|artillery shell, or unguided rocket.