The United Kingdom simultaneously deployed three of its four Vanguard-class nuclear-powered ballistic missile submarines—HMS Vanguard, HMS Vigilant, and HMS Vengeance—at sea in October 2026.

From the articleThree of UK's four nuclear submarines are out at sea in ‘unusual’ move: ReportAlso in Why are three of the UK’s four nuclear deterrent submarines at sea?, Why the deployment of 3 UK nuclear submarines is raising eyebrows, Three of UK's four nuclear submarines out at sea