HMNB Portsmouth the military and naval units destined for Sword Beach on the Normandy coast as a part of Operation Overlord and the D-Day landings on 6 June 1944. Troops destined for each of the landing beaches left from Portsmouth aboard vessels such as the armed merchant cruisers HMCS "Prince Henry" and HMCS "Prince David", escorted by the Canadian destroyers HMCS "Algonquin" and "Sioux". The majority of the naval support for the operation left from Portsmouth, including the Mulberry Harbours. Boathouse 4 (built around the start of hostilities) contributed to the construction of landing craft and support vessels as well as more
Erwin Rommel at Calais. Although Hitler himself expected a Normandy invasion for a while, Rommel and most Army commanders in France believed there would be two invasions, with the main invasion coming at the Pas-de-Calais. Rommel drove defensive preparations all along the coast of Northern France, particularly concentrating fortification building in the River Somme estuary. By D-Day on 6 June 1944 nearly all the German staff officers, including Hitler's staff, believed that Pas-de-Calais was going to be the main invasion site, and continued to believe so even after the landings in Normandy had occurred. The 5 June storm in the channel seemed