What was the major disagreement between the United States and the Soviet Union after World War II?

Recognizing the strong position that the Soviet Army held on the ground, Churchill--and an ailing Roosevelt--agreed to a number of things with Stalin. At Yalta, they granted territorial concessions to the Soviet Union, and outlined punitive measures against Germany, including Allied occupation and the principle of reparations. Stalin guaranteed that the Soviet Union would declare war on Japan within 6 months after the end of hostilities in Europe.

While the diplomats and politicians engaged in trying to shape the postwar world, Soviet forces from the east and Allied forces from the west continued to advance on Germany. After a fierce and costly battle, Berlin fell to Soviet forces on May 8, 1945, after Allied and Soviet troops had met on the Elbe River to shake hands and congratulate each other on a hard won impending victory. Although the war in Europe was over, it would take several more months of hard fighting and substantial losses for Allied forces to defeat the Japanese in September 1945, including the first use of the atomic bomb. In accordance with the Yalta agreements, the Soviet Union declared war on Japan in early August 1945, just prior to Japan’s surrender in September.

The alliance between the United States and the Soviet Union during World War II developed out of necessity, and out of a shared realization that each country needed the other to defeat one of the most dangerous and destructive forces of the twentieth century. Ideological differences were subordinated, albeit temporarily, to the common goal of defeating fascism. As a result of this cooperation, the groundwork for a new international system was laid, out of which came the United Nations organization. The Soviets had suffered tremendous human and material losses during the war. Approximately 20 million people were killed, thousands of villages, towns, and cities were destroyed, and the Soviet Union’s economic infrastructure was devastated. Despite the subsequent postwar controversies and the beginning of the Cold War, nothing can diminish the importance of the wartime cooperation between the United States and the Soviet Union.