Two weeks after the Americans, British, and Canadians invaded Western Europe on D-Day, June 6, 1944, the Soviet Union launched Operation Bagration on the Eastern Front, its massive attempt to clear German forces from Belarus. In one of the largest military campaigns of all time, involving 2 million Soviets and 800,000 Germans, the Red Army advanced 170 miles in two weeks and destroyed German Army Group Center. Using recently declassified Soviet documents...