After cooperating in World War II, the United States and the Soviet Union became antagonists. Immediately after the Potsdam and Yalta agreements in 1945, the Soviet Union consolidated its control in eastern Europe, installing puppet regimes in Soviet-occupied territories. Tensions further heightened when the Soviet Union, under Joseph Stalin, blockaded Berlin and launched a successful Soviet sponsored coup in Czechoslovakia (1948). In 1949 two new German states appeared. The eastern half became the German Democratic Republic, aligning itself with the Soviet Union, whilst the West became the Federal Republic of Germany. West Berlin became an isolated enclave within East Germany. Alarmed by all these developments, US President Harry S. Truman responded by speedily implementing the Marshall Plan, an American initiative which provided over $13 billion in aid to Western Europe to assist with economic reconstruction. The US also joined with western European democracies and Canada in NATO (the North Atlantic Treaty Organization) in 1949. This was to provide military protection to western democracies under threat of Soviet encroachment. Tensions were also heightened by the Soviet distrust of the US; prior to Hiroshima, the Soviets were not aware that their erstwhile allies had the A-bomb. This is the beginning of the ‘cold war’, a non-combat state of geo-political tension between US-led liberal democracies and the Soviet Union and its satellites.
— OR —