United States' atomic bomb program

The United States' atomic bomb program, known as the Manhattan Project, was a top-secret research effort during World War II to develop nuclear weapons. Initiated in 1939 and culminating in 1945, scientists and engineers worked to harness nuclear fission—splitting atoms—to produce powerful explosions. The project involved building advanced facilities and conducting tests across the U.S. Once completed, the bombs were used on Hiroshima and Nagasaki, helping end the war. It marked the beginning of the nuclear age, profoundly impacting international security, diplomacy, and scientific research.