Looking back: Castle Bravo

On March 1, 1954, Castle Bravo, the test of a Los Alamos–designed thermonuclear device named Shrimp, took place on Bikini Island in the Pacific. Shrimp used a new kind of fuel, and scientists miscalculated its yield. They predicted 6 to 7 megatons, but Shrimp detonated at 15 megatons, making Castle Bravo the largest U.S. nuclear test. Its fallout spread over 7,000 square miles, irradiating nearby islanders, servicemen assigned to Operation Castle, and the crew of a Japanese fishing trawler. Public outcry about the incident contributed to efforts culminating in the Limited Test Ban Treaty of 1963, which banned nuclear tests in the atmosphere, underwater, and in space.