Strong coastal defenses forced costly changes to Allied invasion plans

Coastal defenses depended on adequate crews, supporting forces, and defensive layers behind the first positions. Strong defenses at ports and in the Pas-de-Calais helped direct the Allies toward other landing sites. Landing away from a port then created a supply problem, answered at Normandy through the enormous effort of building movable Mulberry harbors. Successful landings reveal only part of this effect: operations abandoned for lack of sufficient force leave no battle to remember. A defense could therefore impose substantial costs and alter enemy plans even when an invasion eventually succeeded.