Why foreknowledge alone would not let Germany stop D-Day

If Germany knew the Allied invasion would strike the French coast, could it change the defenses enough to stop D-Day?

Not reliably; Germany had limited mobile reserves and infrastructure, while the Allies could shift the landing site and concentrate enough naval and ground power against the chosen coast.

Fixed defenses were a tripwire; the decisive question was where Germany could sustain mobile divisions with rail access, workshops, fuel, ammunition, and storage. Moving defenses toward Normandy would weaken other coasts and could simply cause the Allies to choose a different landing area. Omaha was always likely to be the hardest beach because of its terrain, not because it alone possessed a complete garrison. The answer also stresses that shore defenses aim to impose a prohibitive cost and that Overlord combined logistics, deception, naval gunfire, intelligence, geography, and overwhelming force rather than depending on one tactical advantage.