Commander Kruge was a brutally pragmatic Klingon commander who was assigned to steal the secrets of the Genesis Device. To that end, he took his ship to the Genesis Planet, where he destroyed the U.S.S. Grissom and captured Saavik and Dr. David Marcus. He also boarded the stolen U.S.S. Enterprise, only to have most of his men killed when the ship self-destructed. After killing Dr. Marcus, he and James T. Kirk battled on the rapidly crumbling Genesis Planet, and Kruge fell to his death.