Strax

Commander Strax was a Sontaran commander who was demoted to nurse as punishment for an unspecified failure. He was one of many people who owed the Doctor a debt. He was tending to human soldiers on a battlefield when he was summoned by the Doctor to help in the mission to rescue Amy and her baby at Demon's Run. He was mortally wounded in the battle with the Headless monks when one damaged his probic vent. In his final moments, Strax noted how he longed to die in combat, and now, he didn't find it as enjoyable as he thought. Rory tried to comfort him, saying he was a good warrior, but Strax insisted he was a lowly nurse. (DW: A Good Man Goes to War)