Weakened by the war, the Dutch in Indonesia, the British in India and the French in Vietnam found that they could not contain independence movements. In the next decades, dozens of other colonies would also claim self-government
Meanwhile, Europe and Japan had been destroyed by WWII. Germany was divided. Conflict increased between the U.S. and its WWII ally, the communist USSR, over removing Soviet troops from Iran, USSR support for the communist insurgency in Greece, and attempts by the USSR to control the straits between the Black Sea and the Mediterranean. Ideological differences and mistrust between Truman and Stalin were also factors.
But the most important events occurred in the late 1940s, when the Russia-led USSR imposed puppet communist regimes in the countries of Eastern Europe. This was the primary cause of the Cold War. In this bipolar conflict, each side tried to stop the other from gaining territory or influence, and each saw the other’s moves as a threat to their own existence. The two rival powers engaged in proxy wars and a variety of ideological, political, economic and other conflicts that dominated world politics for the next 43 years. However, it remained a Cold War because the two sides never fought each other directly.
Diplomat George Kennan wrote about attempted Soviet expansion and articulated the overall U.S. policy of containment. For example, in the 1940s the U.S. developed the Marshall Plan of aid to rebuild Europe and prevent Communist Party election victories. The Truman Doctrine gave military aid to any country under threat. The NATO military alliance was organized. There was the 1948 Berlin Airlift to supply the city during a Soviet blockade. A key turning point was the 1950-52 Korean War, when North Korea invaded the South and there was extensive fighting between Communist Chinese and U.S. troops when the U.S. penetrated close to the Chinese border.
The CIA backed coups (government overthrows) in Iran in 1952, Guatemala in 1954, Brazil in 1964, Indonesia in 1965 and Chile in 1973; attempted an invasion (the disastrous Bay of Pigs in Cuba in 1961); pushed for assassinations of radical leaders like Congo’s Patrice Lumumba; and subsidized friendly political parties and publications.
The closest the two sides came to actual nuclear war was the Cuban Missile Crisis of 1962, when the USSR set up nuclear missiles in Cuba and the U.S. set up a naval blockade and successfully demanded that the USSR remove them. One positive result from this was the 1963 Atmospheric Test Ban Treaty. One negative result was a large arms buildup by the USSR to reach parity with the U.S.
The U.S. was also involved in the Vietnam War from 1962-73, at a cost of 58,000 American lives. The U.S. saw Vietnam as part of the Cold War with the USSR, when it was primarily a nationalist war against foreign occupation by the French and then the Americans. The rebel leadership had become Communists in their pursuit of independence, so the Russians and Chinese backed them. As part of Cold War strategy, Eisenhower supported the partition of Vietnam, Kennedy backed South Vietnam with aid and advisors, and Johnson and Nixon escalated with bombings and large numbers of U.S. combat troops. However, the increased casualties and lack of progress in the war resulted in a loss of morale among the troops and an aggressive antiwar movement at home (including many Vietnam War veterans such as future Secretary of State John Kerry). Nixon won the 1968 election by promising to end the war, but continued it for another five years. When the U.S. left in 1973 and stopped providing aid to South Vietnam, it collapsed and was taken over by the North.
Meanwhile, in the 1940s the USSR set up its own trade and military alliances in Eastern Europe and harshly suppressed rebellions in East Germany, Hungary, Czechoslovakia and Poland over the following decades. The Russians also built the Berlin Wall in 1961 to prevent East Germans from escaping to the free and prosperous West.
Today, it is difficult to convey the sense of threat that existed during the Cold War years. Each side believed the other wanted to attack them. Each side spied on the other and found spies in their midst. After the USSR exploded its own atomic bomb in 1949, both sides built up their nuclear forces and carried out extensive civil defense construction and operations to guard against nuclear attacks. Students did ‘duck-and-cover’ drills in classrooms by hiding under wooden desks, in a futile attempt to protect themselves from vaporization by nuclear fireballs five miles wide. All public buildings had fallout shelters in the basement, with canned water and boxes of biscuits. (Like thousands of others, my uncle built a fallout shelter in his back yard.) The U.S. Strategic Air Command kept one-third of its nuclear bombers in the air 24/7 for 40 years, with another third on 10-minute standby. Both sides tried to check the other in Western Europe, Japan, Iran, Greece, Turkey, Berlin, Korea, Cuba, Congo, etc. Communists took over China in 1949, leading to a burst of recriminations and fear in the United States. Many innocent Americans lost their jobs when demagogues such as Senator Joseph McCarthy accused them of being communists.