Skaak

Skaak was a Sontaran Commander in charge of the fleet involved during the time invasion of the Crimean War.

Biography
After Ritskaw led the attack on Earth during the events of the Flux, (TV: The Halloween Apocalypse) Skaak led the charge against the British Army in Sevastopol, during the Crimean War in 1855. He chose the Crimea both because he believed it to be the most appropriate starting point, and also because he wanted to ride a horse. During the conflict, Skaak was informed by Svild that the Doctor was present in the time period and was requesting a parlay. Skaak agreed, but shot Svild dead at his request. He did meet with the Doctor, where he explained despite Earth's defiance, they still had a claim on the planet. The Doctor was led away by General Logan, and the British Army were all but wiped out by Skaak's fleet.

After the Thirteenth Doctor constructed a plan to sabotage and drain the Sontarans' energy supplies, Skaak was forced to make a "tactical retreat". As they were doing so, Skaak and his army were all killed when their ships were blown up by General Logan. (TV: War of the Sontarans)