Continuous at sea deterrent 50: what you need to know

Known as Operation Relentless, at least one Royal Navy ballistic submarine has been patrolling the world’s oceans, unseen and undetected for 50 years. CASD is the longest sustained military operation ever undertaken by the UK.

CASD 50 was officially launched on 16 January 2019 when the First Sea Lord visited HM Naval Base Clyde to highlight the 50 year anniversary and present Royal Navy submariners with the new, silver, deterrent pin which will be awarded to those who have completed ten or more patrols.

The history of the UK’s nuclear deterrent stretches back to 1958 and the signing of the UK and US Mutual Defence Agreement (MDA). The MDA led the 2 countries to exchange nuclear information, technology and materials for the greater good. The MDA also paved the way for the signing of the Polaris Sales Agreement (PSA) on 6 April 1963. The agreement saw the UK design and produce its own warheads and construct nuclear powered submarines to host the Polaris system.

Construction on the Resolution-class of ballistic submarines began soon after at Vickers Armstrong in Barrow and Cammell Laird in Birkenhead. The first boat, HMS Resolution, was launched in September 1966 and completed her first deterrent patrol in June 1968. By 1969 the UK began CASD with the 4 Resolution class boats, HMS Resolution, HMS Repulse, HMS Renown, and HMS Revenge, successfully completing over 229 patrols between them. All 4 submarines were ported and operated from HM Naval Base Clyde on the Gareloch.

Work on the next generation of nuclear powered ballistic submarines also began with the first of class, HMS Vanguard, launched on 4 March 1992. Her sister boats HMS Vengeance, Vigilant and Victorious followed and CASD was handed over to a new generation of Royal Navy submariners.

All 4 Vanguard class boats are based at HM Naval Base Clyde and are operated by the Faslane Flotilla. The naval base exists to support CASD and all the units and departments based at Clyde have a role to play.

From 2020 HM Naval Base Clyde will host all the Royal Navy’s attack submarines and will be the future home of the Dreadnought class of nuclear deterrent submarines, which will gradually replace the Vanguard class.