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
D-Day naval deceptions the western flank of the true invasion fleet. This operation was intended to lend confusion as to the extent of the landings in Normandy. Glimmer and Taxable were very similar operations. They were executed in the early hours of 6 June 1944 whilst the invasion fleet was approaching Normandy. Taxable simulated an invasion force approaching Cap d'Antifer and Glimmer threatened Pas-de-Calais. By dropping chaff in progressive patterns, Royal Air Force (RAF) bombers were able to create the illusion of a large fleet on coastal radar screens. Beneath the chaff, small boats towed radar reflector balloons and simulated the radio traffic