Who caused the Cold War?

The Cold War emerged out of mutual distrust on both sides. In 1945, the Soviet Union now stood on military parity with the Western Allies as well as holding most of eastern Europe. The United States feared a potential Communist invasion into the West and Stalin feared the West invading the USSR as Hitler had done. The US using Atomic bombs at Hiroshima and Nagasaki are seen by some as the first volley in the Cold War while others see the emergence of the Iron Curtain by the new Warsaw Pact as the beginning. But both sides feared another war so soon after the end of the most costly war to date and wanted to curb any potential conflict however they could.