1. Franklin D. Roosevelt (United States): President of the United States.
2. Joseph Stalin (Soviet Union): General Secretary of the Communist Party of the Soviet Union.
3. Winston Churchill (United Kingdom): Prime Minister of the United Kingdom.
These three leaders held significant influence in shaping the post-war world order, negotiating on various matters such as the division of Germany, the formation of the United Nations, and the establishment of spheres of influence in Eastern Europe and Asia.