Known as “Mulberry harbors,” these were entirely prefabricated harbors built and assembled in England, moved across, and intended to be set up in mere days. Ramp made to offload ships at one of the Mulberry Harbors, via Institution of Civil Engineers UK With the sites selected down to the most minute detail and the ports designed in England, they would be assembled in pieces, with each harbor consisting of breakwaters made up of scuttled ships and reinforced concrete floats, piers, and even floating roads to connect each section.
So fine was the preparation and detail put into planning that a number of Royal Engineers landed on one of the beaches at night just to collect samples of sand to decide if the beach was suitable to support armored vehicles. Over the winter of 1943/1944, several excursions were made to determine just what locations along the Normandy coast would be suitable for constructing these harbors on D-day. Leaving little to chance, a number of beach surveys were conducted in secret using a small, eleven-meter-long boat. This in and of itself was an undertaking unlike any other before, as no amphibious invasion in history had required the construction of port facilities to offload such immense amounts of supplies and manpower. With no available ports to support a massive invasion of continental Europe, the Allies devised an impressive and thus far unseen solution to the issue of resupply they would make ports of their own. Because of this, German defenses were sensibly centered around the region’s ports, and it is likewise this very reason why the Allies chose to invade across Normandy on D-day rather than nearby major ports of Cherbourg, Le Havre, or Calais. Until this point, it was common belief that a naval invasion would require the taking of a major port city within a very short time after the landings in order to keep the attacker’s forces supplied. It was here that Operation Overlord would make some of its most impressive measures. While it might be possible to land troops in France, keeping them combat-ready was another matter entirely without a port from which to land supplies, ammunition, and reinforcements. There was, however, still one large obstacle to overcome: the question of resupply and logistical support. Thanks to many of the hard lessons learned at Dieppe by the Canadians, the forces invading France were far better prepared and experienced for Operation Neptune.
Prior to the D-day landings, the skies themselves had been filled with aircraft as some twenty-five thousand American, British, and Canadian paratroopers were dropped across the region to take and hold various points of importance so that the landing might succeed. Across five beachheads on the coast of Normandy, one hundred and fifty thousand soldiers would land with the support of nearly two hundred thousand naval personnel from virtually every western Allied nation against some fifty-thousand German defenders. Massive amounts of war material and manpower had been moved and organized for the largest naval invasion the world had ever seen.
The landings of D-day were the product of months spent preparing, planning, and misleading German forces by the Allies. D-day: The Day of Days Allied troops landing in France, via National World War 2 Museum, New Orleans