After world war two, the alliance between the USSR and the West was conflicted. Competition between the Soviet Union and the United States over ideologies, through other countries, without direct armed conflict arose. Both groups began to doubt each other; the United States did not trust communists and the USSR did not trust capitalists. The blame to this event can probably be debated, but from research, the Soviets hold most of the blame. There were many different causes of the Cold War. One of them being the fear the West had of the spread of communism. To prevent the communism to spread, the West, led by USA, adopted a containment policy to hold back its expansion. In 1947, president Truman of USA announced a doctrine of resistance to Communist aggression which guaranteed American aid to all free nations resisting Communism. Rivalry was also a big cause of the war. The USSR and the West started to jockey for position in a postwar world. This emerging competition for control of foreign governments and systems, as well as resources, began the Cold War. The rivalry between the two groups created fear of being attacked by one another. The blame for the Cold War is debatable. Yet, the USSR seems to hold more of the blame than the West. After WWII, the Soviets were really worried about invasion from the west and so they wanted to dominate Eastern Europe. When they begun to spread communism, the West responded and opposed the influence. The Soviets were the ones to start things off. Nevertheless, after the USSR started to spread, the West had to respond. As self defense, the West created the NATO (North Atlantic Treaty Organization). The USSR responded with the Warsaw Pact. Most of the tactics the West was creating were as self defense and preparations for an attack from the Soviets.