were lost when the converted troopship Lancastria was sunk in June 1940, the greatest maritime disaster in Britain's history. The Navy's most critical struggle was the Battle of the Atlantic defending Britain's vital North American commercial supply lines against U-boat attack. A traditional convoy system was instituted from the start of the war, but German submarine tactics, based on group attacks by "wolf-packs", were much more effective than in the previous war, and the threat remained serious for well over three years. Since 1945 After the Second World War, the decline of the British Empire and the economic hardships in Britain forced the reduction in the size and capability of the Royal Navy. The United States Navy instead took on the role of global naval power. Governments since have faced increasing budgetary pressures, partly due to the increasing cost of weapons systems. In 1981, Defence Secretary John Nott had advocated and initiated a series of cutbacks to the Navy. The Falklands War however proved a need for the Royal Navy to regain an expeditionary and littoral capability which, with its resources and structure at the time, would prove difficult. At the beginning of the 1980s, the Royal Navy was a force focused on blue-water anti-submarine warfare. Its purpose was to search for and destroy Soviet submarines in the North Atlantic, and to operate the nuclear deterrent submarine force. The navy received its first nuclear weapons with the introduction of the first of the s armed with the Polaris missile. Post-Cold War Following the conclusion of the Cold War, the Royal Navy began to experience a gradual decline in its fleet size in accordance with the changed strategic environment it operated in. While new and more capable ships are continually brought into service, such as the s, s, and Type 45 destroyers, the total number of ships and submarines operated has continued to steadily reduce. This has caused considerable debate about the size of the Royal Navy, with a 2013 report finding that the current RN was already too small, and that Britain would have to depend on her allies if her territories were attacked. The financial costs attached to nuclear deterrence have become an increasingly significant issue for the navy. Royal Navy today Personnel at Torpoint, Cornwall, is the basic training facility for newly enlisted ratings. Britannia Royal Naval College is the initial officer training establishment for the navy, located