How did World War II Lead to the Cold War?
After World War II why did the Soviets and Allies mistrust each other and how did this apprehension lead to the Cold War? The Cold War (1945-1991) represented a series of localized conflicts and intense diplomatic rivalries between camps led by the capitalist United States and the Communist Soviet Union. This era also saw a massive increase in civilian and military technology, including thousands of nuclear weapons and the means to deliver them across the planet.
This era was largely an outgrowth of the previous decades, with a special focus on the roles the United States and the Soviet Union played in the Second World War. As Europe and Asia prepared for a long rebuilding process both sides offered their own visions for a postwar reality and security.
The Soviet Union under dictator Josef Stalin had several overarching goals and fears in the waning days of the Second World War. Stalin kept in mind the devastation that Russia faced in successive crises including the First World War and Russian Civil War. Stalin had a particular distrust for the Western Allies due to intervention by these powers against the Reds in the Russian Civil War and for abandoning Czechoslovakia before the war began. These are among the factors that pushed Stalin into signing a non-aggression pact with Germany in 1941. Now facing betrayal by Hitler, massive destruction, and about 20 million military and civilian deaths, the Soviet Union was in a unique position. Soviet Red Army troops now occupied almost half of Europe and were the largest military force in the world. 
As Soviet troops displaced German ones Stalin promised free and fair elections across Eastern Europe. In some places, the exiled government returned and limited elections were held. However, many of these governments were forced into coalition governments with Communist-led Popular Fronts. Within several years these Popular Fronts seized power in every country occupied by Soviet troops and installed regimes loyal to Stalin.
The Question of Germany
Germany had invaded Russia twice in less than thirty years, causing millions of deaths. Furthermore, Germany was largely destroyed by the current war, with nearly twelve million killed in the conflict. Ethnic Germans were expulsed from various regions of Eastern Europe, especially in Poland and Czechoslovakia, two regimes soon to be loyal to Stalin.
Stalin's terms were harsh. The Soviets controlled the largest of the four Allied Occupation Zones, including half of Berlin and all of its environs. Stalin was not opposed to a unified Germany, but one that was completely deindustrialized and demilitarized. The United States and the United Kingdom sought instead to reintegrate Germany into the world community unlike after 1918 but also to have it serve as a bulwark against the spread of Communism. The two sides were at an impasse, leading Stalin to ratchet up the pressure. In 1948 the Soviet Union blocked land routes to East Berlin, testing President Truman. Truman responded by organizing the Berlin Airlift. The effort led by the U.S. and U.K. was the largest such effort in history until that point, delivering over 200,000 flights to feed the civilians of Berlin. Stalin's gamble had failed and by 1949 ended the blockade. Distrust between the two sides continued as each zone of occupation solidified around their occupying forces. By 1949, the three Western Allied zones combined to form the Communist-dominated German Democratic Republic and the Western-backed German Federal Republic. 
The United States had not intended to become involved in the conflict in 1939. The 1941 attack on Pearl Harbor led to massive American involvement in both the Atlantic and Pacific Wars. Propping up the Western Allies, U.S.-led troops occupied most of Western Europe, Greece, and much of Asia. President Roosevelt and his successor Harry Truman were led by a combination of democratic idealism with the harsh reality of the failures of the Treaty of Versailles. Seeking to learn from the mistakes from the end of World War I and the interwar era, the U.S. served as a stabilizing force against post-war chaos and Soviet expansionism.
The United States propped up a number of democratic capitalist states in Europe. The Americans also pressed for free and fair elections across the Soviet-occupied zones but with the understanding that this may not be realistic. American intelligence services heavily leaned on elections held in Europe, especially in Italy and France to avoid a Communist Party victory. The United States also introduced the Marshall Plan, a massive rebuilding project across Europe starting in 1948. This plan offered funding, equipment, and technical assistance across Europe, including for former Axis states, Allied states, neutral countries, and the U.S.S.R. and its satellites. Stalin rejected this aid and forced the Eastern European states to do the same. By the time the program wound down in 1951, the U.S. gave $13 billion in many forms of assistance. The Marshall Plan effectively restarted the European economy, allowing industrial and agricultural production to surpass prewar levels and beyond. This laid the foundation for a massive boom, including the future German “economic miracle.” 
First Signs of Conflict
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The differing zones of occupation and goals invariably led to the first conflicts of the Cold War. Greece was engulfed by a civil war between pro-Western and Communist factions. The Soviets also threatened Turkey over the rights to the important Black Sea straits. It was due to this situation that President Truman announced the Truman Doctrine in 1947. The United States offered substantial military assistance to both nations to prevent an expansion of Soviet influence. With this aid, coupled with economic help, communism did not spread in either country. The two sides solidified into alliances: the Warsaw Pact dominated by the Soviets and the North Atlantic Treaty Organization-led by the U.S. 
There were similar seeds of conflict in East Asia. Soviet troops occupied much of China and Korea. Local communist forces had stayed in place in much of Vietnam. While the Nationalist faction in China was friendly with both the U.S.S.R. and the U.S., the Communist Party of China won a series of victories against the Nationalists in the re-emerging Chinese Civil War. By 1948 the Communists had effectively won the conflict, confining the Nationalist Republic of China to Taiwan. Furthermore, the Soviet forces in Korea established a client state in the northern half, the Democratic People's Republic of Korea. In 1950 as American forces largely left Korea, the North invaded the South.
Proxy conflicts and espionage erupted around the globe during the Cold War. The early posturing and saber rattling proved to be a template for future action by the Soviet Union, the United States, and their allies. As the conflict continued many of the first sites of tension erupted into wide-ranging diplomatic and military conflict.
- Hopf, Ted. Reconstructing the Cold War: The Early Years, 1945-1958 Oxford: Oxford University Press, 2012. Page 45-48.
- Harrington, Daniel. Berlin on the Brink: The Blockade, the Airlift, and the Early Cold War. Lexington Kentucky: University Press of Kentucky, 2012. Page 77.
- Kindleberger, Charles. Marshall Plan Days, New York: Routledge, 1987. Page 66.
- Caldwell, Curt, NSC 68 and the Political Economy of the Early Cold War. Cambridge: Cambridge University Press, 2011. Page 211-215.