The Defiant was the ship that helped expand Star Trek: Deep Space Nine from a slice-of-life piece about life in the Federation to a show that had legs and could explore beyond just their docking pylons. It morphed the show that was supposedly just about life on a Starfleet space station during the end of a Cardassian occupation, to a hybrid that combined both the best elements of a series like Next Generation and Babylon 5.
Throughout the latter part of the series, the small battleship known as the Defiant became a huge piece of the show, with its sets being the home to many iconic moments. Including, but not limited to, Captain Sisko’s “You betrayed your uniform!” speech.
So it was surprising when the showrunners opted to blow up the ship in the waning episodes of the series. It was the end of a much-beloved ship.
Until it wasn’t.
Destroying a ship isn’t new in Star Trek. The second Enterprise (NCC-1701) was destroyed in Star Trek III: The Search for Spock, while the NCC-1701-D was destroyed in Star Trek: Generations (ironically ten years apart). These moments were huge for the films. They were then replaced by sleeker ships, better designed for the needs of making films and not television.
Yet, when the Defiant was destroyed, it wasn’t replaced with a new ship. In fact, it wasn’t replaced at all. It was the same ship. Down to the name.
The crew of Deep Space Nine were then gifted a “similar” ship, named the Sao Paulo. Sisko requested and was given a name change for the vessel, and the ship was re-named the Defiant. According to ship-naming customs, however, the ship should’ve been called The Defiant-A.
Why wasn’t this the case?
According to the Star Trek: Deep Space Nine Companion, published in 2000, it was simple. They just didn’t have the money to touch up all the footage with the Defiant to add the “-A”.
According to showrunner and series executive producer, Ira Steven Behr (via Screenrant), they just had to deal with the fact they couldn’t accurately rename the ship with a handful of episodes left in the series.
"We had to bite the bullet. We didn’t have to end the series without the ship… but we weren’t going to build a new ship at the end of the show, and we weren’t going to change the decals."
Ronald D. Moore, who was the show’s executive producer, fought for the “-A”, as he’s a Star Trek aficionado and wanted to respect the established norm, but Behr couldn’t justify the cost. Sometimes the biggest changes happen for the smallest reasons.