Star Trek: Deep Space Nine's USS Defiant is the best-known starship by that name, but Star Trek's original USS Defiant impacted two Star Trek timelines. The Defiant Class NX-74205 USS Defiant debuted in Star Trek: Deep Space Nine season 3. A heavily-armed warship designed, in part, by Captain Benjamin Sisko (Avery Brooks), the USS Defiant was the prototype of a new starship class designed to fight the Borg. DS9 repurposed the Defiant as Sisko's main weapon against the Dominion.
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However, Star Trek: The Original Series introduced the first USS Defiant. A Constitution Class deep space heavy cruiser similar to Captain James T. Kirk's (William Shatner) USS Enterprise, the USS Defiant NCC-1764 encountered the Tholians, with the crew going insane and killing each other. The Defiant was then trapped in a spatial interphase and vanished in Star Trek: The Original Series' "The Thiolian Web." Over 30 years later, Star Trek: Enterprise revealed what happened to the first USS Defiant.
Star Trek’s 23rd Century USS Defiant Was Captured By The Mirror Universe’s Terran Empire
The USS Defiant Is How The Terrans Learned About The Federation
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Star Trek: Enterprise season 4's two-parter, "In a Mirror, Darkly," takes place in the Mirror Universe, which is where the USS Defiant arrived. Further, the Defiant not only jumped to an alternate reality, but it traveled back in time about a hundred years to the 22nd century, where it was captured by the Tholians. Commander Jonathan Archer (Scott Bakula) of the ISS Enterprise successfully commandeered the Defiant. Archer's plan was to use the 23rd-century starship's advanced weaponry to make himself Terran Emperor.
Ensign Hoshi Sato betrayed Archer and subsequently used the USS Defiant to install herself as Terran Empress.
A century later, Star Trek: Discovery revealed the Terran Empire ruled by Emperor Philippa Georgiou (Michelle Yeoh) was more powerful than ever, having conquered most of their galactic rivals like the Klingons and Andorians. This was largely due to the Terrans reaping the technology of the USS Defiant, which gave the Terran fleet more fearsome and deadly weapons. Further, the Terrans learned about Star Trek's Prime Universe and the United Federation of Planets from the data in the Defiant's computers. The Terrans knew about the Federation long before Starfleet learned of the Mirror Universe's existence.
Star Trek: DS9 Had Another Defiant In The Mirror Universe
The ISS Defiant Helped Liberate The Terrans From The Klingons & Cardassians
While Star Trek hasn't defined what ultimately happened to the original USS Defiant in the Mirror Universe, the alternate reality continued the Defiant's legacy. Star Trek: Deep Space Nine's Mirror Universe saga revealed that the Terrans were conquered by the Klingon and Cardassian Alliance led by the Regent, Worf (Michael Dorn). The Terran resistance built their own version of Captain Sisko's Defiant Class starship, the ISS Defiant. Sisko himself had to be brought to the Mirror Universe to make the overpowered Defiant's systems function properly.
Just as Captain Sisko's two versions of the USS Defiant were a lynchpin of the Federation's victory in the Dominion War, the ISS Defiant was instrumental in the Terrans defeating the Alliance. The ISS Defiant helped force the Regent's surrender, which led to the restoration of the Terran Empire. Star Trek: Deep Space Nine ensured that the Defiant had a legacy in both Star Trek's Prime Universe and the Mirror Universe.
