Premise: After months of planning and build-up, Supreme Commander Dwight Eisenhower set Operation Overlord for June 6, 1944: some 7000 ships in the British Isles set to sea and sailed across the English Channel, and, under the leadership of Field Marshall Bernard Montgomery, 135,000 troops landed and stormed Feldmarschal Erwin Rommel's German positions along 80 km of the Normandy coast.
Hypothesis: Erwin Rommel was surprised by Operation Overlord.