Prolonged negotiations result in physical, mental and psychological strain. Those in better physical shape have an advantage of those who are in poor physical shape. As World War II was coming to a close, it was Joseph Stalin who had twice summoned the ailing, wheelchair-bound Franklin Roosevelt around the world to his very doorstep in rapid succession. Some historians believe that Stalin purposely called for Roosevelt to make a second very difficult journey to Yalta (February 4-11, 1945) after Stalin observed how weak Roosevelt appeared in Tehran (November 28 - December 1, 1943) in an attempt to sideline Roosevelt. Indeed, Roosevelt died on April 12, 1945, shortly after he returned from Yalta.