Japanese warplanes attack US fleet at Pearl Harbour in Hawaii, leading to US joining World War II against the Axis powers.
1945
1947
US drops two atomic bombs on Hiroshima and Nagasaki. Japan surrenders.
US enunciates policy of aid for nations it deems threatened by communism in what became known as the Truman Doctrine. Cold War with Soviet Union begins.
1948
1950-54
1950-53
America ;s programme to revive ailing post-war European economies - the Marshall Plan - comes into force. Some $13bn is disbursed over four years and the plan is regarded as a success.
Senator Joseph McCarthy carries out a crusade against alleged communists in government and public life; the campaign and its methods become known as McCarthyism. In 1954 McCarthy is formally censured by the Senate.
US forces play leading role against North Korean and Chinese troops in Korean War.
