Cobb ( The Doctor ' s Daughter ) General Cobb was a general encountered by the Tenth Doctor , Donna and later Martha on the planet Messaline . He commanded Cline and the Doctor ' s daughter , Jenny . Donna called him " Captain Nutjob " after he had her and her friends arrested and spoke of a desire for genocide against the Hath . When Cline captured the Doctor and Donna , he took them to see Cobb , who assumed they , along with Jenny , were pacifists from the Eastern Zone . Cobb asked the Doctor to join his army in the war against the alien Hath . He sought the Source . He believed the Source would give him the power to kill every Hath on the planet . When the Doctor refused to help and instead spoke of stopping him , Cobb had the Doctor , Donna and Jenny arrested for not supporting him in the war . Cobb later found Cline tied up on the floor of the cell , discovering that the three of them had broken out . Cline said Jenny had tricked him . Cobb and his soldiers chased the Doctor , Donna and Jenny into secret passageways uncovered by the Doctor . When Jenny tried to buy them time by holding up the soldiers , she hesitated to kill Cobb . He tried to convince her to join his cause , stating that it was " in [ her ] blood " . Jenny was already loyal to her father , the Doctor , and he had told her there was always a choice in killing someone . Instead , she hit a pipe to delay Cobb and his troops . When the Doctor told Cobb that if the Source was a weapon he ' d never let him have it , Cobb threatened to kill him . The Doctor , Donna and Jenny were reunited with Martha and found the Source first . They discovered it was a terraforming device . The Doctor declared the war over and released the terraforming device . Cobb blamed the Doctor for ruining his chance at victory and tried to shoot him . Jenny stood in the way to protect her father so Cobb shot her . She was shot through one of her hearts and temporarily killed . The Doctor held a gun to Cobb ' s head and contemplated killing him , then stopped , telling Cobb that " [ he ] never would " and that it was on that basis that the new society of human and Hath should he founded . Cobb was demoted , arrested and imprisoned for Jenny ' s murder . ( TV : " The Doctor ' s Daughter " ) Personality . Cobb was a vicious , xenophobic and desperate soldier who detested the Hath . He was a hypocrite who claimed that he wanted to restore peace to Messaline , when all he really wanted was to destroy the Hath , as shown when he told the Doctor that he wanted the war won rather than over . He was a tough soldier who was very hard to intimidate , as shown when he casually brushed off the Doctor ' s threat to interfere with his plan , merely considering it ironic that he was the one who had shown them the way . He took pride in Jenny at first , wishing he had more soldiers like him in his squad . However , he nonetheless locked her up with the Doctor and Donna as he believed she was of " pacifist stock " and couldn ' t be trusted . After being denied his murder of the Hath , he showed a vengeful side when he attempted to kill the Doctor , but only temporarily killed Jenny instead . ( TV : " The Doctor ' s Daughter " )