In 1954, the United States detonated Castle Bravo at Bikini Atoll expecting a far smaller blast, but the weapon exploded with a 15-megaton yield and became the largest nuclear test in U.S. history.

On July 16, 1945, the first nuclear explosion occurred a few hundred miles south of Los Alamos, New Mexico. Known as the Trinity test by J. Robert Oppenheimer, the director of the Los Alamos ...