During the time of the Imperial Era, the Imperial installation named Sentinel Base maintained a flotilla under its command. In 14 BBY, the Core Envoy, which was Sentinel's Imperial-class Star Destroyer, was absent from the base along with the majority of the flotilla's capital ships; they were providing escort for supply convoys headed to the planet of Geonosis, the construction site of an Imperial battle station that would later be known as the Death Star.
While the greater portion of the flotilla was not present, Sentinel Base suffered an attack from a rebel cell. The only ships available to the base at the time were the spacetug Fremond, the frigate Salliche, and the Venator-class Star Destroyer named Electrum. Moff Wilhuff Tarkin, the commander of the base, deployed the Electrum to counter the attack.
The first appearance of Sentinel Base's flotilla was in the 2014 novel, Tarkin, by James Luceno.