"Cold War" is the eighth episode of the seventh series of the British science-fiction television drama 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.

"Cold War" reintroduces the Ice Warriors, who were last seen in the Third Doctor serial The Monster of Peladon (1974). Bringing back the monsters was Gatiss' idea, and he convinced executive producer Steven Moffat by coming up with new things to do with them. The Ice Warriors' costume was improved but not significantly redesigned, as the production team felt they were not well known enough. The episode was filmed in June 2012 on a submarine set, as the story is a closed "base-under-siege". "Cold War" was watched by 7.37 million viewers and received generally positive reviews from critics.

A Soviet submarine is sailing near the North Pole in 1983 during the Cold War. A nuclear weapons launch drill they are running is interrupted by Professor Grisenko (David Warner). In the submarine's cargo hold a sailor prematurely begins to defrost a block of ice that Grisenko believes contains a frozen mammoth, and is attacked by what is inside.

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