The War Headquarters Tunnels are a vast rock-hewn underground complex situated beneath the Upper Barracca Gardens in Valletta. Encompassing a total area of 35,000 square meters of tunneling, it served as the Combined Headquarters for Britain's three fighting services between August 1940 and May 1943. This included the Royal Navy's Operations Room, the Royal Artillery Coastal Defence and Anti-aircraft Gun Operation Rooms, and the Royal Air Force's Fighter Operations' and Filter Rooms. Throughout the Siege of 1940-43, this headquarters played a pivotal role in the defence of Malta. In May 1943, it was superseded by the more spacious and strategically laid out Lascaris War Rooms, located nearby. The latter was completed in time for its utilisation in Operation Husky, the invasion of Sicily on 9/10 July.