Cold War started shortly after World War II. The United States and the Soviet Union were allies at that time because the biggest threat to both countries - and to all of Europe - was Nazi Germany. Hitler had to be stopped and the United States and the Soviet Union joined forces to crush Germany. And then the war ended and the decisions needed to be made as to how European nations would be supervised by or taken over by; so it was up to the communist Soviet Union and the capitalist U.S. To make those strategic arrangements. Who would have the greatest influence in Europe? That was the question that really led to the tensions driving the Cold War.
At the Yalta conference in February 1945, there was no firm agreement; and at the Potsdam Conference in July 1945, the argument over the future of Germany and Eastern Europe grew into a tense situation between President Harry Truman and Soviet dictator Stalin. After that meeting ended in angry words, the U.S. exploded two atomic bombs on Japan, creating further tensions between the two superpowers.
Truman's Marshall Plan (helping Europeans rebuild with food and supplies) and Truman's aid sent to the Greek military (helping them defeat communists) showed the U.S. was willing to stand up to the Soviets. When the U.S. tried to unite East and West Germany, Stalin build a blockade into West Berlin, but the U.S. flew supplies in over the blockade to keep their influence strong in Germany. The Soviets resented that. The entire buildup of bad feelings between the two superpowers was ideological and political. The communists wanted to spread their influence, and they began supporting revolutionary movements in Africa, Asia, and in Latin America, to expand communism. President Eisenhower in the 1950s threatened to use nuclear weapons if the Soviets intervened in the Middle East during the Suez Crisis. Basically, the U.S. And Soviets challenged each other to go one better each time a new move was made; it was like a chess match, only the loser might have been both countries because the Soviets had the atomic bomb by 1949, and if one attacked the other, no doubt the retaliation would be severe, and perhaps wipe out millions of people. The Cold War ended in around 1989, when Soviet President Gorbachev introduced reforms and democracy.
