ABLE test, Bikini Atoll, July 25, 1946 (b/w photo)

Operation Crossroads was a series of nuclear weapons tests conducted by the United States at Bikini Atoll in the Marshall Islands in 1946. The purpose of the operation, which included two shots, ABLE and BAKER, was to investigate the effect of nuclear weapons on naval warships. They were the first tests to be publicly announced beforehand and observed by an invited audience, which included a large press corps. The first test, codenamed ABLE, occurred on July 1, 1946 when an implosion-type atomic bomb (named Gilda) was dropped from a B-29 and detonated over the target fleet at an altitude of 520 feet with a yield of 23 kilotons. The ABLE test went smoothly, although the test weapon was dropped between 1,500 and 2,000 feet off the target ship in the middle of the lagoon.