, but the Soviet possessed a huge conventional armed force, a seemingly threatening the ideology, and, by 1949, atomic weapons. The uneasy alliance that had existed between the United States and the Soviet Union during World War ll, followed by suspicious maneuvering during the first few years after the war, was replaced by overt hostility. Indeed, the rivalry that divided much of the world into two antagonistic spheres was so bitter that it became known as the cold war, a conflict with the hatred but not the military clashes of a "hot war The exact causes of the confrontation termed the cold war are complex and controversial. It is safe to say, however, that varying economic and political interests and the power vacuum created by the collapse of the old balance-of-power structure created a bipolar system in which a great deal of world politics was centered on the confrontation between the two superpowers The American reaction to the perceived world Soviet communist threat was the containment doctrine.