Information about the UK’s continuous at sea deterrent (CASD) and the Successor program 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.
The continuous at sea deterrent (CASD) has provided the United Kingdom’s ultimate security insurance policy every day for the last 46 years.
Since 1992 the 4 boats of the Vanguard Class have maintained CASD, ensuring at all times 1 submarine was deployed. As the Vanguard submarines progress to the end of their lifespan, the UK is looking at the next generation of submarines to carry forward the vital role. This is called the Successor submarine program.