Cobb (The Doctor's Daughter)
Cobb was a general encountered by the Doctor, Donna on the planet Messaline. He commanded Cline and the Doctor's daughter, Jenny.
Cobb asked the Doctor to join them in the war against the alien Hath. He sought "the Source" and it was his mission to get it. He had the Doctor and Donna arrested along with Jenny for not supporting him in the war. As he found out that the three of them had broke out he chased them down into secret passageways.
When Jenny hesitated before shooting him, he shot and (temporarily) killed her. The Doctor and Cobb was demoted and locked away.(DW: The Doctor's Daughter)
Other information
We do not know that, while his soldiers appeared young, Cobb appeared middle-aged, yet still appeared to believe in the same myths as his troopers.
Behind the Scenes
Some fans have noticed that Cobb shares the same name as Jayne Cobb, a similarly thuggish character from another cult science fiction television series, Firefly.