The Tehran Conference, held in 1943, was the first of three major World War II conferences attended by the 'Big Three' Allied leaders: Joseph Stalin of the Soviet Union, Franklin D. Roosevelt of the United States, and Winston Churchill of the United Kingdom. The CAIRO Conference, held in 1943, was the second of the three major World War II conferences attended by the 'Big Three' Allied leaders. The Yalta Conference, held in 1945, was the third of the three major World War II conferences attended by the 'Big Three' Allied leaders. All three conferences were held to discuss the post-war reorganization of Europe and the defeat of Nazi Germany.