Hartzer began his career in the Starfleet Marine Corps where he rose to the rank of captain. He gained a reputation across the marine service as a skilled tactician, and was simultaneously decorated and reprimanded for reckless courage on two separate occasions during a number of different police actions.
Following these events, he served in a garrison on Solis II. Here he participated in a training exercise, but Hartzer's unit was badly defeated. Shortly afterwards he was arrested for the murder of fellow officer. A psychological examination determined that Hartzer was deeply disturbed, even psychotic, and he was sentenced to confinement at a Federation treatment center. But Hartzer escaped during transportation and went his own way.
However, he dreamed of returning to a military career, particularly in command. With Starfleet out of the question, he decided to become a mercenary outside the Federation, and hoped to one day form his own mercenary force. To this end, to gain enough money, he signed on with the pirate vessel Werewolf as part of its boarding party. He was under the impression that he was in charge, though his fellow pirates disagreed.
Hartzer was arrogant and vain, and styled himself as "The Baron", sometimes even wearing a monocle as an affectation. He also had a sadistic streak, both in combat and in victory, which he was likely to inflict it on captives for their so-called "insolent resistance".