Editing Star Trek: Deep Space Nine (section)

===The Dominion War===
{{Main|Dominion War}}
The second-season episode "[[Rules of Acquisition (Star Trek: Deep Space Nine)|Rules of Acquisition]]" marks the first mention of the [[Dominion (Star Trek)|Dominion]], a ruthless empire in the Gamma Quadrant, though they are not fully introduced until the second-season finale, "[[The Jem'Hadar]]". It is led by "the Founders", a race of shape-shifting Changelings, the same species as ''DS9''{{'}}s security chief, Odo. They were once persecuted by non-shapeshifters (whom they call "solids") and they seek to impose "order" upon any who could potentially harm them, which includes nearly all solids. The Founders have created or genetically modified races to serve them: their sly diplomats and administrators, the [[Vorta]], and their fearless shock troops, the [[Jem'Hadar]]. These races worship the Founders as gods.

At the start of ''DS9''{{'}}s third season ("[[The Search (Star Trek: Deep Space Nine)|The Search]]"), with the threat of a Dominion attack looming from the other side of the wormhole, the [[USS Defiant|USS ''Defiant'']], a prototype warship, is stationed at ''Deep Space Nine'', providing an avenue for plot lines away from the station. With the third season, writers from the now-completed ''The Next Generation'' began to write regularly for ''DS9''.

In the show's middle seasons, the Dominion foments discord to weaken the Alpha Quadrant powers, manipulating the Klingons into war with the Cardassians, and almost inciting a ''coup d'état'' on Earth. In the fifth-season episode "[[By Inferno's Light]]", the Dominion annexes Cardassia, and goes to war with the other major powers of the Alpha Quadrant in the season finale "[[Call to Arms (Star Trek: Deep Space Nine)|Call to Arms]]". The Dominion War tests Starfleet's commitment to its ethics; when the formerly neutral [[Romulan]]s are persuaded to ally themselves with the Federation ("[[In the Pale Moonlight]]"), it occurs only through criminal and duplicitous acts on Sisko's part. This provides an example of the moral ambiguity prevalent in ''DS9'' in comparison to the other ''Star Trek'' series.