The Cold War began after World War II, leaving the United States and the Soviet Union two of the strongest allies fighting the Axis. Even though they had strong alliance relations, the two countries did not always share the same ideas. For example, the United States disagreed that the Soviet Union was a communist country under the rule of Joseph Stalin while it believed in capitalism. The United States had no leverage over the Soviet power and was one of the strongest countries militarily at the time. The Soviet Union held grudges against the United States, such as not entering the war soon enough resulting in the deaths of many Russian soldiers, which also added tension to their alliance. Tensions within their alliance soon became the cause of the Cold War. First, the United States feared that the Russians would try to take control and influence the popularity of communism in other countries. Then there is that fear had become reality when the Soviet Union aimed to increase the control of communism and spread it throughout the world. The United States had developed the atomic bomb and dropped it on Hiroshima and Nagasaki, while the Soviet Union wanted to obtain information. If the Soviet Union had had access, it could have used the atomic bomb to force the spread of communism. The Soviet Union also expanded after the war into countries that would soon be introduced to communism, and the United States did not want communism to spread from a different father than the one it already had. The Soviet Union wanted to expand its borders to gain more protection. The two countries had completely opposite ideas on how to govern and manage a country, which in return created chaos and was the main cause of the Cold War. The need for power was... at the heart of the card... their actions. The Soviet Union tried to spread communism throughout the world and the United States stepped in and created the Truman Doctrine in which they stated that they would contain any further spread of communism. The United States was trying to protect other countries from communist control. After World War II, the United States developed the Marshall Plan to provide economic aid to Europe and Russia. However, the Soviet Union rejected their offer and did not accept the help offered by the United States, increasing tension between the two. He later claimed that the United States had not offered enough help to the Soviet Union, when in fact it had. America is also guilty of trying to interfere with how Stalin ruled Russia. It was his choice to conform to communism over his people, just as the United States chose capitalism.