The father of General Martok, a commoner from the Ketha lowlands of Qo'noS who dreamed his son would become an officer and died before seeing him win a battlefield commission.
Urthog was a Klingon of the Ketha lowlands on Qo'noS, a poor district whose families had served the Empire as common soldiers for generations. His ambition was for his son Martok to be the first of them to become an officer.
Martok tells the story in the Deep Space Nine episode Once More Unto the Breach. With the sponsorship of an officer he applied to the academy and passed the entrance trials, only for the application to be struck down by a single member of the oversight council, the aristocratic Kor, who would not admit a lowlander. The rejection barred Martok even from enlisting, and he spent five years as a civilian labourer on a general's flagship before earning a commission in battle. By then Urthog was dead.
Urthog is never seen; the tale explains Martok's long hatred of Kor.