Cold War
After the World War II, countries, from which the major part was totally ruined, had two choices: wither the USA or the Soviet Union. These two Great Powers could survive the loss that had been caused by the war and since then they had their own duel. This was the beginning of the era of the Cold War. Its first conflict was the blockade in Berlin which was solved by an airlift. Fortunately, the Allied Powers could come to an agreement with Moscow. In 1949, the USA and most of the West-European countries founded the North Atlantic Treaty Organization (NATO). Its aim was the protection of Europe from the Soviet invasion. The opponent reacted with the Warsaw Pact.
The Great Powers didn't meet each other, they agreed in omission of nuclear bombs to avoid environmental pollution. They supported local wars economically and with military powers. Vietnam was also an area of showdown of communism and the capitalist system.
At the end of the 80s, the disadvantages were visible beyond the Iron Curtain. The Soviet planned economy failed continuously. They eventually imported American cereals, factories were run down, maintaining them was just burden for the state budget. The member-states declared their independence one after the other. The action of military powers resulted more and more demonstrations and movements in the other member-states. The Soviet Union collapsed after a 69-year existence.
In the other communist countries the situation became differentiated though. In Europe the governments were changed whereas in Asia the communist power strengthened and remained.