The Royal Navy Submarine Service is one of the five fighting arms of the Royal Navy. It is sometimes known as the Silent Service, as submarines are generally required to operate undetected. The service operates six fleet submarines (SSNs), of the and es (with two further Astute-class boats currently under construction), and four ballistic missile submarines (SSBN), of the . All of these submarines are nuclear powered. Since 1993 the post of Flag Officer Submarines has been dual-hatted with the post of Commander Operations. The Royal Navy's senior submariner was for many years located at in Hampshire. It moved from Dolphin to the Northwood Headquarters in 1978. The Submarine School is now at at Torpoint in Cornwall. History In 1900 the Royal Navy ordered five submarines from Vickers Shipbuilding and Engineering of Barrow-in-Furness, designed by Electric Boat Company. The following year the first submarine, , was launched, and the navy recruited six officers for the Submarine Service, under Reginald Bacon as Inspecting Captain of Submarines. At the beginning of World War I it consisted of 168 officers, 1250 ratings, and 62 submarines. During the war it was awarded five of the Royal Navy's 14 Victoria Crosses of the war, the first to Lieutenant Norman Holbrook, Commanding Officer of . In the Mediterranean (during the Siege of Malta), British U-class submarines began operations against Italy as early as January 1941. Larger submarines began operations in 1940, but after 50% losses per mission, they were withdrawn. U-class submarines operated from the Manoel Island Base known as HMS Talbot. Unfortunately no bomb-proof pens were available as the building project had been scrapped before the war, owing to cost-cutting policies. The new force was named the Tenth Submarine Flotilla and was placed under Flag Officer Submarines, Admiral Max Horton, who appointed Commander George Simpson to command the unit. Administratively, the Tenth Flotilla operated under the First Submarine Flotilla at Alexandria, itself under the admiral commanding in the Mediterranean, Andrew Cunningham. In reality, Cunningham gave Simpson and his unit a free hand. Until U-class vessels could be made available in numbers, British T-class submarines were used. They had successes, but suffered heavy losses when they began operations on 20 September 1940. Owing to the shortage of torpedoes, enemy ships could not be attacked unless the target in question was a warship, tanker or other "significant vessel". The flotilla's performance of the fleet was mixed at