Yalta Conference
Roosevelt, Churchill and Stalin met at Yalta in Crimea and agreed on the occupation of Germany, the founding of the UN and Soviet entry into the war against Japan, laying the foundations of the post-war order and the Cold War.

U.S. Army Signal Corps Collection · Public domain · Source
In February 1945, with Germany’s defeat in sight, the three leaders met at the Livadia Palace. Germany would be divided into zones occupied by the US, Britain, the USSR and France, and a conference would found the United Nations. The Soviet Union would enter the war against Japan within two or three months of Germany’s surrender in return for southern Sakhalin and the Kuril Islands.
Poland’s borders were to move west and free elections were to be held, but a Soviet-backed government took power. Korea was not on the formal agenda, though Roosevelt and Stalin are said to have discussed a trusteeship. As Eastern Europe passed into the Soviet sphere, the Yalta settlement became the starting point of the Cold War order.