Overview:Allies encircle the Ruhr, Germany's industrial heartland. U.S. landings on Okinawa put U.S. forces on the Emperor's doorstep. A look at tanks, the work horses of World War II. America mourns as FDR dies in April 1945. Roosevelt was in the beginning months of his fourth term. Harry Truman acceded to the Presidency and a few months later would make one of the most momentous decisions in history.