The United States Atomic Energy Commission , directed by David E. Lilienthal until 1950 , was in charge of designing and building nuclear weapons under a policy of full civilian control . The U.S. had only 9 atomic bombs in 1946 , but the stockpile grew to 650 by 1951 . Lilienthal wanted to give high priority to peaceful uses for nuclear technology , especially nuclear power plants , but coal was cheap and the power industry was largely uninterested in building nuclear power plants during the Truman administration . Construction of the first nuclear plant would not begin until 1954 . In early 1950 , Truman authorized the development of thermonuclear weapons , a more powerful version of atomic bombs . Truman 's decision to develop thermonuclear weapons faced opposition from many liberals and some government officials , but he believed that the Soviet Union would likely develop the weapons and was unwilling to allow the Soviets to have such an advantage . The first test of thermonuclear weaponry was conducted by the United States in 1952 ; the Soviet Union would perform its own thermonuclear test in August 1953
first test
Ivy Mike
Presidency of Harry S. Truman