The atomic bombings of Japan in 1945 ended World War II and marked the beginning of a new era where nuclear weapons shape global power competition and national security from the Cold War through today.
Following the war, the U.S. held a nuclear weapons monopoly, although it did not have a viable nuclear capability and lacked clear doctrine. Initially, atomic weapons were viewed as immensely powerful conventional bombs to be integrated into existing strategic bombing and targeting frameworks. Over time, this thinking evolved as the unique and enduring, destructive and psychological effects of nuclear weapons became clear, and the concept of strategic deterrence emerged from the recognition that nuclear weapons could prevent war by threatening catastrophic retaliation.
