UK nuclear deterrence (CASD)

Information about the UK’s continuous at sea deterrent (CASD) and the Dreadnought programme to replace the Royal Navy’s Trident missile Vanguard Class Submarines.

The protection and defence of the UK is a primary responsibility of the government. The government is committed to maintaining the UK’s national nuclear deterrent based on a ballistic missile submarine for as long as the global security situation makes that necessary.

For half a century the Royal Navy has been entrusted with the country’s number one defence priority, the maintenance and operation of the UK’s most formidable weapon and final line of defence.

Since the mid ’90s, the 4 boats of the Vanguard Class have maintained CASD, ensuring 1 submarine was deployed at all times. The Dreadnought class are expected to enter service in the early 2030s.

The 4 new boats will continue the unbroken chain of CASD far into the future and continue to help ensure the security of generations to come.

The UK government is investing millions of pounds at HM Naval Base Clyde with the development increasing the numbers at the site to an eventual population of around 8,500.

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.


Read the full National Security Strategy and Strategic Defence and Security Review 2015 here.

CASD 50: what you need to know

2019 marks the 50 year anniversary of the Continuous At Sea Deterrent (CASD 50).



UK Nuclear Deterrence Policy Hub

A full list of policy and related documents is available here.

Dreadnought submarine programme

Published 26 February 2016
Last updated 3 May 2019 + show all updates
  1. Updated with the latest CASD 50 announcement information.

  2. Updated nuclear deterrent information as of 14 February 2018.

  3. Added The United Kingdom’s future nuclear deterrent: 2017 update to Parliament.

  4. Added The United Kingdom’s future nuclear deterrent: 2016 update to Parliament

  5. Added speech for The case for the retention of the UK's independent nuclear deterrent.

  6. Added news article.

  7. First published.