"Cold War" is the ninth episode of the seventh series of Doctor Who, starring Matt Smith as The Eleventh Doctor and Jenna-Louise Coleman as Clara Oswald. The episode was written by Mark Gatiss, a frequent writer and sometimes actor for the show.

The show takes place onboard a Soviet submarine in the Arctic in the year 1983, giving a dual meaning to the title. A third meaning is presented when we find out there is an Ice Warrior, a classic Who monster, aboard the submarine as well. Fortunately, the TARDIS materializes, dropping a confused Doctor and Clara aboard the submarine, which also happens to be sinking and taking on water. The Russian crew of the submarine are obviously suspicious, and the Doctor must ease their fears and deal with an angry alien hunting in the sinking submarine.

This is probably the most used Doctor Who storyline ever: the Base Under Siege, with a side theme of The Doctor having to get warring parties to come to peace. But in Doctor Who, the most predictable things can still be made very good. And within this episode's predictable set-up, I found myself not knowing how it would end. It had a genuine suspense to it that is not always present in Doctor Who.

There is some type of odd polynomial formula for Doctor Who. A Doctor Who episode that takes itself too seriously can often become schmaltzy and melodramatic. A Doctor Who episode that nods too much to the ridiculousness of the show can become camp and kitsch. This episode, despite a few humorous moments, manages to be serious without becoming too serious. I think one of the defining moments of the episode came early on: ten seconds after appearing unexpectedly on a crashing submarine, the Doctor assesses the situation and shouts out to the Captain the one way to save his ship. The Doctor is often portrayed as an eccentric or humorous character, but this moment established him as what he is: a brilliant alien who can solve a life or death problem in a matter of seconds. This episode continued in that manner, with The Doctor portraying his more serious side, all framed by the claustrophobic setting of a sinking, predator-haunted submarine.

I can't really justify why I like this episode: I am sure for many, the spectacular scenery of the previous episode, and its colorful set of characters, would have been more appealing, and this would have seemed somewhat monotonous and formulaic. But for whatever reason, I consider this to be one of the strongest episodes of the season.