At the end of World War II, the main goal for the United States was to set up a world order in which as many countries as possible (particularly in Europe) would be democratic.  At the same time, the Soviet Union’s main goal was to protect itself.  It had been invaded from the west by Germany in WWI and WWII (as well as by France in 1812).  It therefore feared the West, particularly since many countries of the West were anti-communist.

These goals came into conflict with one another.  The Soviet Union wanted to create a buffer zone of states that it controlled in Eastern Europe.  Therefore, it did not want those countries to become democratic.  Meanwhile, the US wanted the countries to be democratic.  The US saw the Soviets’ move as evidence of Soviet aggression and desire to dominate the world.  The Soviets saw US desires as evidence of Western aggression and desire to eliminate communism.  These divergent goals and perceptions helped cause the Cold War.