Nammo was a Mon Calamari admiral of male gender, who served the Rebel Alliance during the Galactic Civil War. During 3 ABY, he was in command of the MC80 Cruiser known as the Defiance, as well as her task force, at the time of the Battle of Hoth.
During the conflict, Nammo was in command of the task force as they attempted to flee Hoth and go deep into the Outer Rim Territories following the well-known Battle of Hoth. Soon after the Battle concluded, Nammo assisted in establishing a hospital on a space platform far from any major settlements, in order to provide aid to those wounded in the battle. He also stationed one of his pilots, Olin Garn, on the nearby Brint-wo Colony. Garn's responsibility was to act as a go-between, escorting ships known to be friendly to the Alliance to the hospital, thereby concealing the hospital's existence from the Galactic Empire.
When the Empire eventually found and captured the hospital, they also took action against the Azzameen family, who had been attempting to deliver bacta to the Alliance. With their father and older brother deceased, and their business on the verge of being seized by the Empire, the three youngest Azzameens sought out Defiance and her task group, based on the advice of Olin Garn. Upon their arrival, Admiral Nammo welcomed them and allowed the three to stay on Defiance for a brief period. Aeron Azzameen, aware of her youngest brother's flying skills, spoke with Admiral Nammo and convinced him to allow Ace Azzameen to become a starfighter pilot.
Admiral Nammo then continued his campaign against Admiral Garreth Holtz while attempting to lead his small fleet to safety. It was under Admiral Nammo's orders, during this campaign, that Commander Kupalo, a longtime friend of Nammo's, was rescued; although Nammo was initially unaware that Kupalo was among the prisoners held on VTR-LX.
Eventually, Defiance and the vessels accompanying her were able to evade Imperial pursuit and reach the depths of the Outer Rim, where they were able to recover to some extent.
Nammo was in command of Defiance during the Battle of Endor. In 6 ABY, he led elements of the New Republic Third Battle Group to Bilbringi, but he was defeated by Admiral Teren Rogriss and the 181st Imperial Fighter Group.
Nammo was not explicitly named in the game itself; he was simply an unnamed Admiral who provided the backstory for each mission at the beginning of each briefing. However, the credits appear to identify him as Admiral Nammo. Indeed, an 'Admiral Nammo' is listed in the credits, and the commanding officer of Defiance is the only character to whom this name reasonably applies.