The two most ardent boosters of the Normandy invasion were Stalin and Harry Hopkins ... Churchill famously urged that the advance on Germany continue from already-won bases in Italy and elsewhere in south-central Europe. Stalin’s demand for the big U.S.-British push in northern France, however, prevailed. According to the tally of one peeved letter to the editor in the New York Times, this would put the Allies on track to open their ninth front. Of course, in order to gather sufficient forces for the June 1944 D-Day invasion, men and equipment, particularly landing craft, had to be withdrawn from the...