The Manhattan Project

In the summer of 1939, Albert Einstein signed a letter to President Roosevelt warning that Germany might be developing a weapon of unprecedented destructive power using nuclear fission. The letter eventually produced the Manhattan Project — a secret research and industrial program employing more than 130,000 people at sites across the United States and Canada, costing $2 billion (roughly $28 billion today), and producing in three years what physicists had considered theoretically possible for less than a decade. On July 16, 1945, at the Trinity test site in New Mexico, the world's first nuclear device detonated. J. Robert Oppenheimer, the project's scientific director, recalled a line from Hindu scripture: "Now I am become Death, the destroyer of worlds."

The organizational achievement matched the scientific one. General Leslie Groves managed an enterprise the size of the American automotive industry with near-total secrecy — Vice President Harry Truman did not learn of the bomb until he became president upon Roosevelt's death in April 1945. The project concentrated physicists of extraordinary ability: Enrico Fermi, Niels Bohr, Richard Feynman, Hans Bethe. Many were European Jews who had fled fascism. They worked with the urgency of people who believed Nazi Germany was ahead of them. Germany surrendered in May 1945. The bomb was not yet ready.

The atomic bombings of Hiroshima on August 6 and Nagasaki on August 9, 1945, killed between 130,000 and 226,000 people, the majority civilians. Japan announced its surrender on August 15. Whether the bombs were necessary to end the war without a land invasion of Japan — and what the human cost of such an invasion would have been — remains one of the most intensely argued questions in American military history. What is not argued is what the Manhattan Project produced: a permanent transformation of war, international relations, and the nature of human risk itself.

The project's scientific legacy runs in two directions. Its physicists went on to build civilian nuclear power, particle accelerators, and the instruments of modern physics research. Its weapon designs produced an arms race that, at its Cold War peak, put more than 60,000 nuclear warheads in existence worldwide. Several Manhattan Project scientists — Oppenheimer among them — spent their postwar careers trying to control what they had created. Oppenheimer's security clearance was revoked in 1954 during the McCarthy era, a humiliation the U.S. government formally rescinded in 2022.