In the Star Trek universe, the Dominion is an interstellar state and military superpower from the Gamma Quadrant, composed of hundreds of dominated alien species. The Dominion is commanded by The Founders, a race of shapeshifters (or Changelings as they are often referred to), responsible for both the creation of the Dominion and all strategic decisions undertaken through its history. The Dominion is administered by the Vorta, clones specifically genetically engineered by the Founders to act as field commanders, administrators, scientists and diplomats. The Jem'Hadar, also engineered by the Founders, are the military arm of the Dominion and one of the most powerful military forces in the galaxy during the Dominion's height.
The Dominion first appeared in season 2, episode 26 "The Jem'Hadar" of the television series Star Trek: Deep Space Nine and ultimately became the primary antagonists of the series until its conclusion. The Dominion waged war on the United Federation of Planets after silently annexing Cardassia in the Alpha Quadrant. The conflict spanned several years and involved many other races including the Klingons and the Romulans.
Dominion War#Conception
In 2002, Star Trek: Deep Space Nine producer Ira Steven Behr stated that unlike some plots, which originated from a single small idea, the creation of the Dominion villain and story arc was "very much thought out." Behr said that the earliest mention of the Dominion was purposely planted in the comic Season Two Ferengi episode, "Rules of Acquisition", to leave the audience with an impression of "how important could it be?" It was decided that the Gamma Quadrant would need an ambience that would distinguish it from the Alpha Quadrant. The producers wanted to portray the region as something other than "uncharted space", and avoid imitating the adventures of Star Trek: The Next Generation with another series of plots focusing primarily on themes of exploration. After 18 months of Deep Space Nine exposition, the producers decided to characterize the Dominion as "anti-Federation".