Jinn Gehenam is first seen in command of the League Militaire ship Gaunland. He received a minor injury and is complaining about it bitterly, berating the lack of prompt assistance from his medical staff. This initial encounter leaves a bad impression on the mobile suit pilot Uso Ewin, who has learned that he is the leader of the League Militaire.
Jinn's position allows him to act as the leader of the League Militaire. When he learns that a Keilas Guilie is being converted into a mega-particle cannon to be used to attack Earth, he immediately orders an attack on the Keilias Guilie. He believes that such an action will allow the League Militaire to garner support from colonies that are sympathetic to their cause. He later attempts to punish Uso and a group he left with in order to find Shahkti Kareen for their reckless actions, but becomes distracted more excited about the idea when he learns that they can use the orbital energy satellite Hiland in order to create a cannon using microwaves to attack the Keilias Guilie.
Shortly after this he attempts to implement the plan, however captain Robert Gomez dissuades him, pointing out the manpower necessary to carry out an attack, Uso recommends they use a ship as a shield in order to protect the other to fire a microwave cannon, but Jinn rejects this idea as well. He agrees and compliments Uso, however he implies a plan to use the microwaves to induce headaches and stomachs to the Keilias Guilie's crew.
When the League Militaire moves to perform more aggressive action to destroy the Keilias Guilie, Jinn becomes excited as they successfully use the unarmed Gaunland in order to destroy the Keilias Guilie fleet by moving it in under remote control and having it self-destruct. He is shocked when he witnesses Uso in battle, not realizing before what his true potential was. As the attack enters a boarding phase, Robert hands him a gun saying that it is "a real battle between soldiers" Jinn responds by becoming emotional and saying he doesn't want it.
As the League Militaire tows in a captured Squid class vessel Jinn renames the new League ship Reinforce Junior. He then enthusiastically uses the ship as a command vessel to use, the now captured Keilias Guilie, to fire on and devastate the Zanscare fleet.
After Uso and company have returned to the Earth, Jinn orders a return to space once Fuala Griffon reappears. He says that it needs to be immediate, but is contradicted by Robert Gomez who says that they can rest for a day. They observe that Karlmann Dukartuse reacts to the "sound" of Fuala's bells which he can "hear". Jinn has Shahkti bring him to the bridge as they attempt to ascertain this.
Shortly after their rally together with the "real Jinn Gehenam", Hangelg Ewin, Jinn becomes more aggressive, want to compete a bit with Hangelg. He orders an attack despite the danger of Fuala, saying that they have the means to combat her. While the old men on the bridge disagree, Robert supports the decision. Ultimately the attack order is issued by Jinn in order to preserve the fiction that he is the actual leader of the League Militaire.
Towards the end of the war the decision is made to launch an attack on the Angel Halo, despite the fact the combined Earth Federation/League Militaire forces are not complete and the fact that Federation reinforcements are on their way. Hangelg explains that he is acting on instinct and believes that with their current forces they can win. Jinn becomes angry and criticizes him for acting on instinct, pointing out the lives that have been sacrificed to bring them this far, however ultimately it is decided to follow Hangelg's judgement.
Jinn's final action comes during the final battle over the Angel Halo. He decides to ram the Adrastea-class with the Reinforce Junior. With his final words he says that, "without this sacrifice everyone will die and they will be forgotten, but as long as the young survive the name of Jinn Gehenam will live forever." He is killed along with the Robert Gomez and the old men who chose to remain on the ship in the ensuing explosion when their vessels collide.
- His name is most likely derived from the word "Gehenna", a valley surrounding Jerusalem's Old City and also a name for the hell.
- Jinn means "Genie" in Arabic.