The Sontaran Stratagem

192a – "The Sontaran Stratagem"
Doctor Who episode
A Sontaran introduces himself to the Doctor as General Staal. The episode reintroduces the Sontarans to the revived series.
Cast
Doctor David Tennant (Tenth Doctor)
Companions Catherine Tate (Donna Noble) Freema Agyeman (Martha Jones)
Others Christopher Ryan – General Staal Rupert Holliday-Evans – Colonel Mace Dan Starkey – Commander Skorr Ryan Sampson – Luke Rattigan Bernard Cribbins – Wilfred Mott Jacqueline King – Sylvia Noble Eleanor Matsuura – Jo Nakashima Christian Cooke – Ross Jenkins Clive Standen – Private Harris Wesley Theobald – Private Gray Ruari Mears – Clone
Production
Directed by	Douglas Mackinnon
Written by	Helen Raynor
Script editor	Nikki Smith
Produced by	Susie Liggat
Executive producer(s)	Russell T Davies Julie Gardner Phil Collinson
Incidental music composer	Murray Gold
Production code	4.4
Series	Series 4
Length	1st of 2-part story, 45 minutes
Originally broadcast	26 April 2008
Chronology
← Preceded by Followed by → "Planet of the Ood" "The Poison Sky"

"The Sontaran Stratagem" is the fourth episode of the fourth series of the British science fiction television series Doctor Who, which depicts the adventures of a time-travelling humanoid alien known as the Doctor. The episode was broadcast on BBC One on 26 April 2008. The episode and its sequel, "The Poison Sky", were written by Helen Raynor, who previously wrote the linked episodes "Daleks in Manhattan" and "Evolution of the Daleks" in the third series.

"The Sontaran Stratagem" features the first appearance of the alien Sontarans to the series since the 1985 Colin Baker story The Two Doctors, as well as former companion Martha Jones (Freema Agyeman), last seen in "Last of the Time Lords". The episode takes place on present-day Earth, where Martha and UNIT summon the Doctor (David Tennant) for assistance concerning ATMOS (Atmospheric Omission System), a revolutionary piece of green technology installed in 400 million cars worldwide. ATMOS is later revealed to be part of a Sontaran plot to poison the atmosphere.

Show runner Russell T Davies had considered making the Sontarans return since the revival of the series and wanted to show changes in Martha's personality after her departure. The episode was viewed by 7.06 million viewers after its original broadcast, with an Appreciation Index of "87". Critics gave generally positive reviews, praising the return of the Sontarans, Christopher Ryan's portrayal as Staal, and Raynor's writing; some stated Raynor improved from her previous episodes.