Three of UK's Four Nuclear Deterrent Submarines Are at Sea Together

Three of the UK's four Vanguard-class nuclear deterrent submarines are at sea together, the first time in five years, according to Al Jazeera. The boats are HMS Vanguard, Vigilant and Vengeance; HMS Victorious is in maintenance. At least one is reported to carry ballistic missiles with nuclear warheads. Sky News said the reason was unclear.