Development of nuclear weapons was the motivation behind early research into nuclear fission which the Manhattan Project during World War II (September 1, 1939 – September 2, 1945) carried out most of the early scientific work on fission chain reactions, culminating in the three events involving fission bombs that occurred during the war.
Manhattan Projektet under 2. verdenskrig (September 1, 1939 – September 2, 1945) udførte det meste af det tidlige videnskabelige arbejde om fissions kædereaktioner, som kulminerede i 3 begivenheder involverende fissionsbomber under krigen.