Bobbie's father, a legendary Martian Marine sergeant major revered as 'a god' by recruits.
Sergeant Major Draper is Bobbie Draper's father, a celebrated Martian Marine who served as first sergeant at the training camp where the chaplain Captain Martens was a boot — remembered by the recruits as "a great man" who was "like a god." Bobbie measures herself against his standard and imagines him wincing at her profanity, which she uses to mask fear; Martens invokes his name to try to reach her.
No physical description is given; known only by his towering reputation as a Marine.
Bobbie's father and moral yardstick, a revered Marine sergeant major.