" The World War II bombs, the only nuclear devices ever used as weapons so far, were airbursts, detonated at about 1,900 feet above the ground.31 The air surrounding the bomb instantly heated to incandescence. This feature is called “the fireball.” This rapidly expanding sphere translated a percentage of the thermal energy into blast energy, or a destructive wave of compressed air moving outward at high speed, capable of knocking over concrete buildings. "

― James Mahaffey , Atomic Accidents: A History of Nuclear Meltdowns and Disasters: From the Ozark Mountains to Fukushima