Final answer:
The Yalta Conference in 1945 led to tensions between the U.S. and the Soviet Union due to conflicting interests over Eastern Europe's future, differing visions for postwar reconstruction, and the subsequent Soviet establishment of Communist regimes in violation of promises made during the conference.
Step-by-step explanation:
The Yalta Conference, held in February 1945, marked a pivotal moment in the deterioration of relations between the United States and the Soviet Union. It laid the foundation for discord that would emerge fully in the Cold War period. While the leaders of the United States, United Kingdom, and Soviet Union met with aims to define a postwar order, serious disputes arose over the fate of Poland and Eastern Europe. The U.S. and Britain emphasized the need for self-government and free elections, while Stalin was focused on securing a Soviet sphere of influence to protect his nation against potential future invasions. Despite Stalin's agreement to permit free elections in Eastern Europe, he later retracted this promise, leading to increased tensions among the Allies.
Stalin's insistence on a Communist-dominated government in Poland and his drive for reparations from Germany contrasted with Roosevelt's wish for Soviet support in the Pacific War and the creation of the United Nations, as well as Churchill's push for democratic freedoms in Eastern Europe. These underlying conflicts at Yalta concerning territorial control, political influence, and postwar reparation plans sparked a fundamental mistrust that worsened after the war, as the Soviet Union established Communist regimes in Eastern Europe, disregarding pledges made during the conference. This betrayal of the Yalta agreements served as one of the catalysts for the decades-long Cold War between the two superpowers.