Causes

6. The nuclear arms race between the United States and the Soviet Union increased tensions. U.S. was determined to be the military leader while the Soviet Union wanted the equal amount of military strength. They both started to build many thermonuclear weapons and created systems for using them.
7. America and the USSR were very fearful of each other. America believed that the USSR´s attempt of keeping Poland as a buffer state was an attempt of the USSR to gain power and the USSR believed that America wanted to increase its own economic power and destroy their way of life and their system. Such fear of the other caused rivalry to form between the two nations and their allies.
8. The Soviet Union wanted various different countries such as Poland to become Communist. This ran against the wants of America who believed that the states should be able to choose by themselves causing tension between the two countries.
9. The Truman administration, and in particular, President Truman himself, detested Stalin and his atrocious actions. As such, they developed an intense dislike for the Communists on the USSR. On the other hand, the Soviets were also quite loathing of the capitalists. Thus, both sides had developed a repulsive and aggressive attitude towards the other. In short, there existed mutual dislike, if not hatred.
10. Both sides strongly possessed a desire to surpass the other side. This manifested itself in the arms race and the space race and so on. However, one of the ultimate goals of each side was to defeat the other side in terms of economical productivity, or simply put, each side wanted to make more money than the other, leading to a very competitive atmosphere.