Vanguard-class submarine

The Vanguard-class is a British class of nuclear-powered ballistic missile submarines (SSBN) in service with the Royal Navy. Each submarine is armed with up to 16 UGM-133 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, which is now owned by BAE Systems. All four subs are based at HM Naval Base Clyde (HMS Neptune), 40 km (25 mi) west of Glasgow, Scotland.

Since the decommissioning of the Royal Air Force WE.177 free-fall thermonuclear weapons in 1998, the four Vanguard submarines are the sole platforms for the United Kingdom's nuclear weapons.

Development

Since the late 1960s, the UK had operated four Resolution class submarines armed with US-built Polaris missiles under the terms of the 1963 Polaris Sales Agreement.

On 10 July 1980, Prime Minister Margaret Thatcher wrote to US President Carter to request the supply of Trident I (C4) missiles on a similar basis for the United Kingdom's next generation ballistic missile submarines. However, in 1982 Thatcher wrote to US President Reagan to request the UK be allowed to procure the improved Trident II (D5) system, which had been accelerated by the US Navy. This was agreed in March 1982. Under the agreement, the United Kingdom made a 5% research and development contribution.