|Test site||NE Lagoon, Bikini Atoll|
|Number of tests||2|
|Test type||Free fall air drop, Underwater|
Operation Crossroads was a series of two nuclear weapon tests conducted by the United States at Bikini Atoll in mid-1946. They were the first nuclear weapon tests since Trinity in July 1945, and the first detonations of nuclear devices since the atomic bombing of Nagasaki on August 9, 1945. The purpose of the tests was to investigate the effect of nuclear weapons on warships.
The Crossroads tests 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. They were conducted by Joint Army/Navy Task Force One, headed by Vice Admiral William H. P. Blandy, rather than by the Manhattan Project, which had developed nuclear weapons during World War II. A fleet of 95 target ships was assembled in Bikini Lagoon and hit with two detonations of Fat Man plutonium implosion-type nuclear weapons of the kind dropped on Nagasaki, each with a yield of 23 kilotons of TNT (96 TJ).
The first test was Able. The bomb, named Gilda after Rita Hayworth's character in the 1946 eponymous film, was dropped from the B-29 Superfortress Dave's Dream of the 509th Bombardment Group on July 1, 1946, and detonated 520 feet (158 m) above the target fleet. It caused less than the expected amount of ship damage because it missed its aim point by 2,130 feet (649 m). The second test was Baker. The bomb, known as Helen of Bikini, was detonated 90 feet (27 m) underwater on July 25, 1946. Radioactive sea spray caused extensive contamination. A third deep water test, Charlie, planned for 1947, was canceled primarily because of the United States Navy's inability to decontaminate the target ships after the Baker test. Ultimately, only nine target ships were able to be scrapped rather than scuttled. Charlie was rescheduled as Operation Wigwam, a deep water shot conducted in 1955 off the California coast.