Active service:
  2371 - 2375

  Captain Benjamin L. Sisko
   2371 - 2375


The USS Defiant NX-74205 was the prototype vessel for the Defiant-class starships. It was Starfleet's first true warship and had no provisions for families or diplomatic missions, no science lab, no holodecks, or any of the other comforts of home. It was a heavily armored, stripped-down vessel that was created as a 'first strike' vehicle for use in war, and incorporated the latest in Starfleet weaponary and defensive technology.

During the battle drills the Defiant nearly tore itself part when the engines were tested at full capacity. Given the serious nature of the design problems and the diminished Borg threat, Starfleet took the decision to suspend work on the Defiant. It wasn't until 2371 after the destruction of the USS Odyssey NCC-71832 by the Jem'Hadar that Starfleet became concerned about the possible threat the Dominion posed. At Captain Sisko's request, the Defiant Project was reinstated and the prototype was stationed at Deep Space 9. Under Sisko's command the Defiant's main role was to protect DS9 and Bajor from a Dominion attack.

The Defiant was the first ship to have a cloaking device installed onboard. According to the provisions in the Treaty of Algeron, the Federation agreed to abstain from developing or using cloaking technology. With the rising threat of the Dominion, the Romulan Star Empire made an agreement to loan Starfleet a cloaking device. The provisions of this agreement included that a Romulan officer be stationed on the Defiant to operate it, that it only be used in the Gamma Quadrant, and all intelligence reports be made available to the Romulan government. It was in 2374 after the Klingon attack in Cardassian space the agreement was modified to include limited use in the Alpha Quadrant. When using the cloaking device the interior lights dimmed, and all defensive power was transferred to the cloak. Because of the Defiant's unusually high power signature the cloaking device could be penetrated by certain types of anti-proton beams. Deactivating main power was the only way to keep the Defiant fully invisible to sensors. While in warp the cloak is extended to mask the warp field.

While initially the Defiant had serious flaws Chief O'Brien and the DS9 engineering team have modified it into a reliable and potent ship. When the Defiant entered the atmosphere of a Class-J planet on stardate 49263 it was severely damaged with few safety and crew support systems.

In the Mirror Universe there also exists a USS Defiant built by the Terran rebels in 2372, used to fight the Alliance. It was built after the Mirror Universe "Smiley" O'Brien stole the plans for the Defiant from DS-9. When it had the same problems as the original Defiant, Captain Sisko was kidnapped and persuaded to help them modify the Defiant to fend off an oncoming Alliance fleet to retake Terok Nor.

Since 2371, the Defiant was one of the most powerful warships in the Alpha Quadrant. In 2373, Lieutenant Commander Worf commanded the Defiant in an attack against a Borg cube heading to Earth. Being badly damaged Worf would have rammed the Defiant into the cube if the USS Enterprise NCC-1701-E had not arrived at the battle when it did. The crew of the Defiant beamed aboard the Enterprise, and the Defiant went into spacedock for repairs and returned to DS-9.

By the end of 2373 the Defiant had gone into production. The USS Valiant NCC-74210, and two other unidentified Defiant-class ships have been seen in active duty. The USS Defiant was destroyed by the Breen while at the Chin'toka System in 2375. The Defiant was quickly replaced with the USS São Paulo NCC-75633, a slightly updated and modified Defiant-class starship assigned to DS9 on stardate 52861. Captain Sisko was given special dispensation by the Chief of Starfleet Operations to rename the São Paulo to Defiant and remains stationed at DS-9 under the command of Colonel Kira.

In "What You Leave Behind", the hull markings for the USS São Paulo read 'USS Defiant NX-74205' because of the extensive use of stock footage used in this episode. Even if there was time to paint the hull markings, the registry should have remained as NCC-75633 or at least NCC-74205-A.

Related Links:
Designing the Defiant, Defiant Problems (EAS)