The Retention functioned as an Interdictor class cruiser for what remained of the Imperial Navy's Seventh Fleet throughout the Galactic Civil War. In the year 3 ABY, at a time when this remnant had been partially exiled from standard Imperial military actions, the Retention participated in a planned ambush targeting a Rebel Alliance convoy located at the astronomical location of Derra IV.
Working alongside the Imperial-class Star Destroyers Vigilance—commanded by Vice Admiral Rae Sloane—and the Dark Omen, the Retention successfully isolated the convoy, which then led to its complete destruction. The ambush was later regarded as one of the most significant victories for the Empire during the war, and the Imperial officers involved were brought back into regular Imperial duties. Historian Beaumont Kin discussed the battle, and the Retention's crucial contribution, in his book titled The Rise and Fall of the Galactic Empire.
The Retention was an Interdictor type vessel, and was designated as a cruiser. This specific kind of starship was equipped with gravity well projectors that had the capability to prevent vessels from initiating hyperspace jumps, and could also pull ships traveling at lightspeed back into realspace.
During the period of the Galactic Civil War, the Retention was a part of the remnant forces of the Imperial Navy's 7th Fleet. Prior to the liberation of the Outer Rim Territories planet Lothal in 1 BBY, the fleet had been under the command of Grand Admiral Thrawn, where a significant portion of the fleet was lost, along with Thrawn himself. Following the conflict, the remaining ships of the fleet, which included a small number of capital ships and support vessels that were not present at Lothal, were placed under the command of Vice Admiral Corf Ferno and tasked by General Cassio Tagge with patrolling the Outer Rim. Subsequently, the fleet was partially exiled from standard Imperial operations and, as a result, worked together with Vice Admiral Rae Sloane, who was similarly exiled, aboard the Imperial-class Star Destroyer Vigilance.
At this point in time, the Alliance to Restore the Republic was in the process of moving essential supplies through the Derra system located in the Outer Rim. These supplies included weapons, various equipment, food, and medicines, with the majority being delivered to the Alliance's hidden base situated on the planet Hoth. Some of these stockpiles were also distributed to other rebel cells. While the Empire was not yet aware of the base's specific location, they recognized that disrupting this supply line would significantly improve their chances of achieving a broader strategic victory. To achieve this goal, Sloane and the 7th Fleet identified potential routes used by rebel shipping in the Expansion Region, ultimately isolating the astronomical object known as Derra IV.
In 3 ABY, Sloane spearheaded an attack on a substantial rebel convoy at Derra IV from the Vigilance, with critical support provided by the ISD Dark Omen and the Retention. The Imperial forces successfully ambushed the Rebel Alliance's respected Renegade Squadron. During the engagement, the Retention played a vital role in isolating the rebel convoy, leading to its complete destruction. This resulted in a resounding victory for the Empire, leading to Sloane's promotion to the rank of full admiral, and the reintegration of her and other Imperial leaders into mainstream Imperial military operations.
Details concerning the ambush, which included the specific role of the Retention, were documented in the file labeled Interrogations 143 within the "Imperial Prisoners" section of the New Republic Archives. In 35 ABY, the historian Beaumont Kin made reference to the Retention when discussing the events at Derra IV in his book The Rise and Fall of the Galactic Empire, utilizing Interrogations 143 as one of his sources. According to Kin's analysis, the Retention was the most important element in the battle's success, which he considered to be among the greatest Imperial victories during the Galactic Civil War.
The Retention was mentioned in Star Wars: The Rise and Fall of the Galactic Empire, a reference 2024 book written by Dr. Chris Kempshall.