During the Galactic Civil War, which pitted the Galactic Empire against the Alliance to Restore the Republic, the Inexorable functioned as an Imperial I-class Star Destroyer within the ranks of the Imperial Navy. It is remembered for two things: its helplessness during the Rebellion's capture of the shuttle Tydirium just prior to the Battle of Endor, and its significant involvement in Grand Admiral Thrawn's campaign against the New Republic around 9 ABY. The Inexorable participated as a key vessel in Thrawn's fleet, seeing action in the battles of Bpfassh and Sluis Van.
The Inexorable conformed to the standard design of an Imperial I-class Star Destroyer. This warship, measuring 1,600 meters in length, was equipped with turbolasers, ion cannons, and tractor beam emitters. It also accommodated a full array of TIE starfighters, ground troops, and various vehicles for terrestrial operations. Due to post-Battle of Endor constraints on the Empire, its TIE fighter complement was reduced from six to three squadrons by 9 ABY.
During the Galactic Civil War, as the Galactic Empire fought the Alliance to Restore the Republic, the Inexorable was being built by the Empire at the Kuat Drive Yards on Kuat. Close to completion in 3 ABY, Shannon Voorson, daughter of Kuat Freight Port officials Johan and Nell Voorson, managed to slice its name, along with the names of other Star Destroyers, into an Imperial database and provide it to her cousin, Deen Voorson, who was a member of the Rebellion.
The Inexorable was observed in 4 ABY participating in weapons trials alongside the Imperial-class Star Destroyers Chimaera, Nemesis, and Stormhawk within the Carida system. Ace Azzameen's ship, the Otana, piloted by the Rebel pilot, mistakenly exited hyperspace in close proximity to these Star Destroyers, but it successfully escaped. The Inexorable pursued the Otana to the Zhar system, but it arrived too late to stop Azzameen and Rebel fighters from stealing the Tydirium. This shuttle was subsequently instrumental in the Rebels' victory at the Battle of Endor.
Following Endor, the Inexorable was part of a small Imperial fleet under the command of Thrawn, a Grand Admiral whose reputation preceded him, during a mission into the Unknown Regions.
Later, the Rebellion transitioned into the New Republic, which then became the recognized galactic authority. In 9 ABY, the Inexorable participated in Grand Admiral Thrawn's campaign against the New Republic after his return to the known galaxy. The Inexorable was one of five Star Destroyers in a task force personally led by the Grand Admiral, with coordination provided by the Dark Jedi Joruus C'baoth. During this campaign, the Inexorable took part in the attack on Bpfassh, where it destroyed a New Republic starfighter base located on the third moon of Bpfassh. Thrawn also utilized the ship to evaluate a prototype cloaking device, using plans obtained from the hidden Imperial storehouse on the planet Wayland. Subsequently, the Inexorable was involved in the Battle of Sluis Van, a failed attempt to commandeer a large fleet of starships at Sluis Van, a significant New Republic shipyard.
As punishment for his "incompetence" in failing to capture Rogue Squadron pilot Bror Jace in 6 ABY, Director of Imperial Intelligence Ysanne Isard decided to reassign Major Wortin from the Interdictor Black Asp to the Inexorable.
The identity of the Inexorable's captain during Thrawn's campaign was not identified by New Republic Intelligence.
The Inexorable first appeared in Timothy Zahn's 1991 novel, Heir to the Empire. While the Heir to the Empire Sourcebook identifies it as a core vessel in Thrawn's fleet, it is not mentioned in the subsequent two books of the Thrawn Trilogy.
Conflicting sources exist regarding the starship class of the Inexorable. The Complete Star Wars Encyclopedia (vol 2, p 101) describes it as an Imperial I-class Star Destroyer, while Star Wars: X-Wing Alliance (Battle 6, Mission 2) and Star Wars: X-Wing Alliance: Prima's Official Strategy Guide (p 175) classify it as an Imperial II-class Star Destroyer.