"Cold War" is the eighth episode of the seventh series of the British science fiction television series Doctor Who. It first aired on BBC One on 13 April 2013, and was written by Mark Gatiss and directed by Douglas Mackinnon. In the episode, alien time traveller the Doctor (Matt Smith) and his companion Clara Oswald (Jenna-Louise Coleman) land on a Soviet submarine in 1983 during the Cold War, where the Ice Warrior Grand Marshal Skaldak breaks loose and plots revenge against humanity.