Cold War began in 1945, at the end of World War II. It is described the intense rivalry that has existed since this date between Communists and non-Communists nations. On one side are the Union of Soviet Socialist Republics and its Communists allies, often referred to as the Eastern bloc, which by the mid 1950's included East Germany, Albania, Hungary, Poland Romania, China, Czechoslovakia, Poland, and Bulgaria. On the other side is the United States along with its democratic allies, including Canada, France, West Germany, the Philippines, Japan, Great Britain, and many other countries of Western Europe and Latin America. This group was usually referred to as the Western bloc. Such intense rivalry is known as the Cold War because it has not actually led to fighting, or "hot " war. .
Characteristics such as mutual distrust, suspicion, and misunderstandings by both the US and the Soviet Union, and their respective allies, describe the Cold War through the years. At times, such conditions have increased the probability of a third world war. Some issues that led to the Cold War are, that the US has accused the U.S.S.R. of seeking to expand Communism throughout the world. Meanwhile, the Soviets have charged the US with practicing imperialism and with attempting to sop revolutionary activity in other countries. Another contribution to the East-West tension is each bloc's vision of the world. On one side, the US, wants a world of independent nations based on democratic principles. On the other, the Soviet Union, has tried to control areas it considers very important to its national interest, including much of Eastern Europe.
In 1941, during WWII, Germany attacked the Soviet Union. For this reason, the Soviet Union joined the Western Allies in fighting Germany. For a time it seemed that some sort of union might develop between the Soviet Union and the US because of their wartime cooperation. But this wasn't possible.