Operation Crossroads was a series of nuclear weapon tests conducted by the United States at Bikini Atoll in mid-1946. It was the first test of a nuclear weapon since the Trinity nuclear test in July 1945, and the first detonation of a nuclear device since the atomic bombing of Nagasaki on August 9, 1945. Its purpose was to investigate the effect of nuclear weapons on naval ships. Crossroads consisted of two detonations, each with a yield of 23 kilotons of TNT (96 TJ): Able was detonated at an altitude of 520 feet (160 m) on July 1, 1946; Baker was detonated 90 feet (27 m) underwater on July 25, 1946. A third burst, Charlie, planned for 1947, was canceled primarily because of the United States Navy's inability to decontaminate the target ships after the Baker test. Charlie was rescheduled as Operation Wigwam, a deep water shot conducted in 1955 off the California coast. The Crossroads tests were the fourth and fifth nuclear explosions conducted by the United States (following the Trinity test and the bombings of Hiroshima and Nagasaki). They were the first of many nuclear tests held in the Marshall Islands and the first to be publicly announced beforehand and observed by an invited audience, including a large press corps. To prepare the atoll for Operation Crossroads, Bikini's native residents agreed to evacuate the island. Many were moved to the Rongerik Atoll. Later, in the 1950s, a series of large thermonuclear tests rendered Bikini unfit for subsistence farming and fishing. Because of radioactive contamination, Bikini remains uninhabited as of 2013, though it is occasionally visited by sport divers. Although there are claims that participants in the Operation Crossroads tests were well protected against radiation sickness, one study showed that the life expectancy of participants was reduced by an average of three months. The Baker test resulted in the radioactive contamination of all the target ships. It was the first case of immediate, concentrated local radioactive fallout from a nuclear explosion. Chemist Glenn Seaborg, the longest-serving chairman of the Atomic Energy Commission, called Baker "the world's first nuclear disaster."
