Trident II D5 (UK)

Trident II D5 is a U.S.-designed submarine-launched ballistic missile used by both the United States and the United Kingdom. The UK deploys Trident D5 from Vanguard-class ballistic missile submarines and plans to continue the missile system with the Dreadnought class. For the United Kingdom, Trident is the core delivery system for its continuous at-sea nuclear deterrent.

Trident II D5 is a three-stage solid-fuel SLBM with inertial guidance and multiple reentry vehicle capability. U.S. Navy fact files list the missile as part of a wider strategic weapon system including shipboard systems, reentry systems, and support infrastructure. British missiles are drawn from a shared pool arrangement with the United States but carry UK-controlled warheads and are deployed under British national command.

Operationally, the UK's Trident force is designed to keep at least one ballistic-missile submarine at sea, making a nuclear attack on the UK impossible to guarantee as disarming. The missile's importance is strategic, not tactical: it underpins deterrence, alliance signaling, and national nuclear policy. Any assessment of the system must include submarine survivability, command authority, warhead policy, and life-extension arrangements.