Castle Bravo was the
code name given to the first United States test of a dry fuel
hydrogen bomb, detonated on March 1, 1954, at
Bikini Atoll,
Marshall Islands, as the first test of
Operation Castle.
Castle Bravo was the most powerful
nuclear device ever detonated by the United States (and just under one-third the energy of the
Tsar Bomba, the most powerful device ever detonated), with a
yield of 15
megatons of TNT. That yield, far exceeding the expected yield of 4 to 8 megatons (6 Mt predicted), combined with other factors, led to the most significant accidental
radioactive contamination ever caused by the United States.