Nuclear Strategy and Weapons

Washington, D.C., September 25, 2025 - Newly published documents and photographs concerning the radiation and blast effects of the August 1945 bombings of Hiroshima and Nagasaki provide graphic details on how U.S. and British officials first assessed the deadly impact of the atomic weapons. These and other records published today are among the data and evidence that helped undermine the public claim made at the time by Manhattan Project director Gen. Leslie Groves that radiation sickness was “a pleasant way to die.”

Washington, D.C., July 16, 2025 - Early in the morning of 16 July 1945, 80 years ago, the U.S. Manhattan Project staged the first test of a nuclear weapon in the New Mexican desert. It was the first trial of a plutonium implosion weapon—the same weapon type that devastated Nagasaki a few weeks later. The explosion on the ground produced radioactive fallout contaminating over 1,100 square miles of the state, with some debris spreading as far north as Canada.

Washington, D.C., June 3, 2025 - The Trump administration’s intention to acquire Greenland, including possibly by force, has put a focus on the history of its strategic interest to U.S. policymakers. Today, the National Security Archive publishes the first of a two-part declassified document collection on the U.S. role in Greenland during the middle years of the Cold War, covering the decisions that led to the secret deployment of U.S.

Washington, D.C., December 17, 2024 - A recently declassified Joint Atomic Energy Intelligence Committee (JAEIC) report from December 1960 is the first and only known U.S. intelligence report to correctly and unequivocally state that Israel’s Dimona nuclear project would include a reprocessing plant for plutonium production and was weapons related. All known, subsequent U.S. intelligence products treated the reprocessing issue as unsettled until the late 1960s, when Israel reached the threshold of a nuclear weapons capability and the U.S.

Washington, D.C., August 8, 2024 – On the week of the 79th commemoration of the U.S. atomic bombings of Hiroshima and Nagasaki, Japan, the National Security Archive today publishes a fascinating new collection of papers from the office files of Leslie Groves, the director of the Manhattan Project, the U.S. effort during World War II to develop and produce the world’s first nuclear weapons.

Washington, D.C., July 16, 2024 - On 16 July 1945, 79 years ago, the United States, under the Manhattan Project, staged the first test of a nuclear weapon in the New Mexican desert. The first trial of a plutonium implosion weapon, the explosion on the ground produced radioactive fallout contaminating over 1,100 square miles of the state, although some debris spread as far north as Canada.

Washington, D.C., May 31, 2024 - On 6 October 1977, President Jimmy Carter and top U.S. national security officials dialed into a secret “Missile Attack Conference” (MAC) to coordinate a response to a simulated surprise nuclear strike on the United States. Organized by the Joint Chiefs of Staff (JCS), the mock war scenario was the first to involve the U.S. President and may have prompted Carter to authorize a retaliatory nuclear missile launch, according to documents posted today by the National Security Archive. 

Washington, D.C., February 29, 2024 - Seventy years ago, on 1 March 1954 (28 February in Washington), the U.S. government detonated a thermonuclear weapon, code-named “Shrimp,” on Bikini Atoll in the Marshall Islands in what turned out to be the largest nuclear test in U.S. history. The Bravo detonation in the Castle test series had an explosive yield of 15 megatons—1,000 times that of the weapon that destroyed Hiroshima and nearly three times the six megatons that its planners estimated.