The Vanguard-class are a class of nuclear-powered ballistic missile submarines (SSBN) in service with the Royal Navy. Each submarine is armed with up to 16 Trident II missiles. The class was introduced in 1994 as part of the UK government's Trident nuclear weapons programme. The class includes four boats: Vanguard, Victorious, Vigilant and Vengeance. They were built at Barrow-in-Furness by Vickers Shipbuilding and Engineering between 1986 and 1999. All four boats are based at HM Naval Base Clyde (HMS Neptune), west of Glasgow, Scotland.