Who caused the Cold War?
The Cold War emerged from the very complex, very tense set of circumstances that characterized the post-World War II world. In particular, it was the product of the new, bipolar postwar order in which the United States and the Soviet Union emerged as the world's two remaining powers. Each of these two superpowers had a very different vision for postwar Europe. They differed over the future of Germany, and particularly over Eastern European nations, which Josef Stalin envisioned as a region of pro-Soviet buffer states.
At the Yalta Conference, Stalin had assured then-President Franklin Roosevelt that free elections would be allowed in Poland. This did not transpire, leading to a dispute at the Potsdam Conference between the Soviets and Harry S. Truman. This dispute, and the fact that the Soviets installed puppet regimes throughout Eastern Europe in the years that followed, is often regarded as the beginning of the Cold War, as it divided Europe into opposing blocs. If one man had to be held accountable for beginning the Cold War, most would probably point to Stalin, but the geopolitical situation in the wake of the war was exceedingly complex and resistant to reductionist explanations.