UK's nuclear deterrent (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.

Defence is the first duty of government, and the threats facing the UK and its allies are increasing in scale, complexity and diversity. We have previously identified risks to the UK from major nuclear armed states, from emerging nuclear states, and state sponsored nuclear terrorism. Those risks have not gone away.

That is why the government is committed to the UK’s independent nuclear deterrent, which has deterred the most extreme threats to our national security and way of life for over 60 years.

Since 1969, the deterrent has been delivered by the Royal Navy, with at least one nuclear-armed ballistic missile submarine patrolling the seas undetected at all times. Their purpose is to preserve peace, prevent coercion, and deter aggression.

The UK’s nuclear deterrent works every hour of every day to guarantee our safety and that of our NATO Allies, with our adversaries knowing that any benefit they may gain from attacking us will be outweighed by the consequences for them.

Since the mid-1990s, 4 Vanguard Class submarines have maintained the deterrent, and a new class of submarine - the Dreadnought class will enter service in the early 2030s.

These new submarines, designed and built in the UK, employ world-leading and cutting-edge technology, and will ensure the nuclear deterrent can be delivered for as long as the global security situation makes it necessary. The UK’s nuclear deterrent is only possible thanks to the skill and dedication of thousands of individuals, from submariners right through the supply chain. Tens of thousands of jobs across the UK are supported by maintaining our nuclear deterrent, and the government continues to invest millions of pounds at HM Naval Base Clyde, the home of the UK’s submarine service and one of the largest employment sites in Scotland.


Dreadnought Submarine Programme

Published 16 March 2021
Last updated 17 March 2021 + show all updates
  1. Added information from the The Integrated Review of Security, Defence, Development and Foreign Policy on the nuclear deterrent.

  2. First published.