Operation Crossroads

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 after the Trinity nuclear test in July 1945, and the first detonation of any nuclear device following the Fat Man detonation 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 Navy's inability to decontaminate the target ships after the Baker test. Crossroads 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 Crossroads, Bikini's native residents agreed to evacuate the island of Bikini. Many were moved by the LST 861 to the island of Rongerik. 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 2011, though it is occasionally visited by sport divers. Although there are claims that participants in the Crossroads tests were well protected against radiation sickness, the Oscar-nominated documentary Radio Bikini showed footage of Navy sailors wearing little or no protection during their inspection of the target ships only hours after the explosions, even though some of the observer ships were caught in the fallout of the Baker explosion. In addition, the documentary revealed that Navy ships used contaminated water from the area for drinking and bathing purposes after the blast. One study showed that the life expectancy of participants was reduced by an average of three months. The test resulted in the radioactive contamination of all the target ships by the underwater Baker shot. 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."