The Defiant was a warship constructed by the Terran rebellion in the mirror universe, based on the Starfleet Defiant-class prototype. (DS9: "Shattered Mirror", "The Emperor's New Cloak") Following the rebels capture of Terok Nor in 2372 they recognised that they were going to need more powerful warships to combat against the eventually Klingon-Cardassian Alliance counterattack to reclaim the station. They started to construct a replica of the Defiant based on schematics "Smiley" O'Brien had "acquired" from his previous visit to the primary universe. The ship ran into the same problems the original Defiant had with been overpowered, with the Alliance bearing down on them the rebellion persuaded Benjamin Sisko from the primary universe to assist in modifying the ship. (DS9: "Shattered Mirror