British hydrogen bomb programme Atomic Energy Act of 1946 (also known as the McMahon Act) ended technical cooperation. Fearing a resurgence of American isolationism, and the loss of Britain's great power status, the British government resumed its own development effort, which was codenamed "High Explosive Research". The successful nuclear test of a British atomic bomb in Operation Hurricane in October 1952 represented an extraordinary scientific and technological achievement. Britain became the world's third nuclear power, reaffirming the country's status as a great power, but hopes that the United States would be sufficiently impressed to restore the nuclear Special Relationship were soon dashed. In November
Operation Upshot–Knothole Operation Upshot–Knothole Operation Upshot–Knothole was a series of eleven nuclear test shots conducted in 1953 at the Nevada Test Site. It followed "Operation Ivy" and preceded "Operation Castle". Over 21,000 soldiers took part in the ground exercise Desert Rock V in conjunction with the "Grable" shot. "Grable" was a 280mm shell fired from the "Atomic Cannon" and was viewed by a number of high-ranking military officials. The test series was notable as containing the first time an atomic artillery shell was fired (shot "Grable"), the first two shots (both fizzles) by University of California Radiation Laboratory—Livermore (now Lawrence Livermore National