As COSSAC developed that plan, the question of where to land posed problems. The site would have to be within the range of fighter aircraft based in Great Britain but also on ground flat enough to construct the airfields that would become necessary once the invading force moved off the beaches and out of the range of its initial fighter support. The landing zones themselves would have to be sheltered from prevailing winds to facilitate around-the-clock resupply operations and would have to possess enough exits to allow the invading force to proceed inland with as little difficulty as possible. Similarly, the area behind the beaches would have to include a road network adequate to the needs of a force that intended to move rapidly. Since the region would ultimately form a base for the drive across France toward Germany, a series of large ports would also have to be close enough to facilitate the unloading of the massive quantities of supplies and ammunition that would be necessary to sustain the attack.
The most appropriate location, COSSAC's planners decided, lay directly across the English Channel from Dover in the Pas de Calais region. The area fulfilled many of the Allies' requirements and offered a direct route into the heart of Germany. Since the enemy had recognized that fact, however, and had already begun to construct heavy fortifications along the coast, an alternative had to be found. The most suitable stood farther to the west, along the Normandy coast near Caen and the Cotentin Peninsula. That region contained major ports at Cherbourg and Le Havre and offered a gateway to ports at Brest, Nantes, L'Orient, and St. Nazaire. Allied planners believed that the Germans would undoubtedly sabotage Cherbourg, forcing the invaders to place heavy initial reliance upon the MULBERRIES, but the damage could be repaired and the region itself was less strongly defended than the Pas de Calais.
Offering, as well, a satisfactory opening into the French interior, it became the site of the invasion.
