During the Galactic Empire's war against the Alliance to Restore the Republic, the Whirlwind was Admiral Harrsk's command ship within the Arrowhead, the intersection of galactic regions the Slice and the Core Worlds. Arrowhead Command was attached to the Imperial Navy's Death Squadron at the Battle of Endor, where the Whirlwind sustained damage, causing an internal explosion that killed the ship's captain Bolla Thoath and drove shrapnel through Harrsk's face and brain. Though conceived as a trap for the Alliance, the Rebels were victorious at Endor, driving the Imperial forces to withdraw. Though Harrsk survived and initially complied with the retreat, he had been driven insane by his injuries and split with the Empire for the galaxy's treacherous Deep Core region, establishing the rogue faction Zero Command.
Eight years after the Battle of Endor, Harrsk's faction was attacked by a fleet of Victory-class Star Destroyers under the command of rival warlord High Admiral Treuten Teradoc—the battle cost Harrsk his flagship, the heavily modified Star Destroyer Shockwave.
Thirsty for revenge, Harrsk took command of his fleet from aboard the Whirlwind—with Admiral Daala assisting from aboard the Star Destroyer Firestorm—and launched a retaliatory strike against Teradoc. While in the midst of the raid, Daala—angry over the chaotic state of the Empire and the loss of her loyal second-in-command, Commander Kratas—disabled the Whirlwind with a volley of ion cannon fire, then opened a comm channel to both Harrsk's and Teradoc's forces requesting an end to in-fighting, and the selection of a commander to lead the remaining Imperial forces against the New Republic; if not such demands were met, she would self-destruct the Firestorm, taking with her Whirlwind and all surrounding vessels.
Following the negotiations at Tsoss Beacon and the reunification of the Deep Core warlords, Whirlwind fell into the hands of the united fleet under Daala and then-Vice Admiral Gilad Pellaeon. It would serve as part of a force of forty-five Star Destroyers under Pellaeon's command, and part of his personal armada of thirteen.