The Cold War had its origins in the extraordinarily turbulent period including the First World War, the Russian Revolutions, and the civil war that broke out in Russia following the Bolshevik seizure of power. The reason this is relevant to a question focused on the post-World War II period is because it is important to keep in mind the fact that suspicions between the Soviet Union and the United States, or between East and West, preceded the outbreak of World War II and the underlying tensions between the two sides contributed directly to the emergence of what became known as the Cold War.
The World War II-era alliance between the United States, Britain, France and other victims of Nazi Germany and the Soviet Union was one of convenience and necessity. Both the Western allies and the Soviet Union had a common enemy in Germany, and the relationship that developed barely disguised the underlying animosity that existed. The United States provided military assistance to the Soviet Union through the Lend-Lease program, and the defeat of Nazi Germany was a shared goal, but there was no love between governments. The Soviet Union, under the brutal dictatorship of Joseph Stalin, was wary of the democratic governments that had opposed the rise of communism and was also scarred by the memories of past invasions by France and Germany. In short, the atmosphere involving the war-time allies was badly tarnished by pre-war history—a situation exacerbated by conflicting visions of a post-World War II Europe and Asia.
Evidence of the impending rupture in the relationship between the United States and Britain on one side and the Soviet Union on the other side was visible in the wartime conferences held between the leaders of these respective nations. During meetings between Presidents Roosevelt and, following Roosevelt’s death, Truman, Prime Minister Churchill, and Soviet leader Stalin, at Tehran, Yalta and Potsdam, the depths of divisions between East and West were very obvious. Stalin sought to maximize Soviet control over the countries of Eastern and Central Europe while the US Britain envisioned the creation of a system of democratic nations coexisting peacefully and economically integrated. The two visions were mutually incompatible, with the post-war arrangement resulting in the emergence of two antagonistic blocs that would define the Cold War.
Key issues, such as the future of Germany, which Stalin continued to mistrust and fear, and of the futures of the Middle East and Asia all contributed to the rising tensions of the time. Stalin was adamant that Germany be divided and kept military weak so that it could never again pose a threat to Russia. The United States and Britain wanted a Germany that would contribute to political stability without presenting a future military threat. As the relationship between East and West continued to deteriorate, those conflicting visions of Germany’s future formed the basis for the superpower showdowns that brought Europe back to the brink of war. As the Soviet Union consolidated its hold on Eastern Europe and proceeded to turn East Germany into a satellite state, the United States increasingly felt it imperative that West Germany be rearmed and made a pillar of what became the North Atlantic alliance, or NATO.
In short, the emergence of the Cold War was the product of many factors, not least of which was the pre-World War II hostility between the democracies of the West and the Communist regime that controlled Russia and its empire, the Soviet Union. Additionally, and of no small degree of importance, Russia’s history of being invaded by France and Germany influenced its perceptions of the more technologically advanced nations to its west, and that history informed Stalin’s perceptions of the countries with which it had been allied for the purpose of defeating Hitler’s Germany. Finally, events in China, where a civil war was leading to the establishment of a communist regime that would, briefly, be close to the Soviet Union, heightened fears in the United States of a growing totalitarian colossus that threatened American interests across much of the world.