Martin Prochnow commands the *Jotunheim*, a civilian cargo ship repurposed for military use by the Principality of Zeon during the One Year War. His vessel belongs to the 603rd Technical Evaluation Unit, field-testing prototype mobile suits, mobile pods, and mobile armors under combat conditions.

Initially welcoming the assignment, Prochnow believed the ship's limited maneuverability would keep it away from direct combat. As the war intensifies, however, the *Jotunheim* is thrust into increasingly intense battle situations. Prochnow prioritizes crew safety over military objectives, exemplified when he ordered a retreat during an early Federation attack to protect personnel. This decision drew criticism from Special Operations Captain Monique Cadillac, who advocated accepting greater risks for Zeon's goals.

His leadership involves managing the ship's diverse crew, including engineers like Lieutenant Oliver May, special operations officers, and civilians. Prochnow maintains a pragmatic outlook on the war, often mediating between the demands of weapons testing and preserving his crew, contrasting with the idealism of some subordinates.

Prochnow witnesses the *Jotunheim*'s involvement in pivotal events, including Operation British and the Battle of Loum. During Loum, his ship deployed the experimental Jormungand plasma cannon, which achieved limited success before mobile suit warfare rendered it obsolete. His command continues through Zeon's retreat, culminating in the Battle of A Baoa Qu where the 603rd Unit covered the evacuation of remaining Zeon forces.

He is an adult man, frequently seen wearing military headgear and possessing facial hair.