|Date:||2373 – 2375|
|Cause:||Dominion build up in Alpha Quadrant|
Federation travel to Gamma Quadrant
|Result:||Cardassian Union occupied|
Dominion barred from Alpha Quadrant
| United Federation of Planets|
Romulan Star Empire
|U.S.S. Defiant||Much of the Cardassian population|
The Dominion War was a major conflict in the Alpha Quadrant that raged from 2373 to 2375 between the Dominion and the Federation Alliance. The Dominion Axis was comprised of the Dominion, Cardassian Union, and the Breen Confederacy. The Federation Alliance was comprised of the United Federation of Planets, Klingon Empire, and eventually the Romulan Star Empire.
When the Dominion was first discovered, they were unhappy with the continued exploration of the Gamma Quadrant. They warned the crew of Deep Space 9 to never return, however, they did. Immediately the Dominion's leaders, The Founders, infiltrated the Alpha Quadrant. Doing so they convinced the Klingon Empire that Cardassia Prime was taken over by the Founders. The Federation explained that Cardassia wasn't under the control of the Dominion, but the Klingons still invaded Cardassia. The Federation Council condemned the invasion. This led to the second Federation-Klingon War. The war ended when it was revealed that the Cardassians allied themselves with the Dominion. Dominion ships began to pour through the wormhole and gather at Cardassia Prime. The Dominion War had just begun.
The Dominion wasted no time, and they attacked Deep Space 9. The battle was won by the Dominion, forcing the Federation to retreat from Bajor. The Federation and Klingons had multiple battles along the Cardassian border, most failed. The Federation and Klingons eventually began to build a fleet to retake DS9 and the wormhole to stop the Dominion reinforcements. Operation Return began poorly, as the Dominion-Cardassian fleet was overpowering the Federation fleet. When it seemed over, the Klingon fleet arrived and dealt a heavy blow to the Cardassian portion. The Defiant went on ahead to DS9 where 2,800 Dominion ships were about to come out of the wormhole. Captain Benjamin Sisko took the Defiant inside the wormhole and begged the Prophets to stop the fleet. And, like he requested, the Dominion fleet disappeared, but were not destroyed. This fleet reappears in the Feature Episode series "The 2800". Without the Dominion reinforcements, the Federation and Klingons took the station back and forced the Dominion to retreat.
After losing DS9 and recruiting the Breen to their side, the Dominion retreated to Cardassia. Then a secret intelligence group named Section 31 infected the "Great Link." The war was a stalemate, with several major battles between the Federation Alliance (now including the Romulans) and the Dominion. This persisted until a Cardassian revolutionist named Legate Damar started a revolution on Cardassia Prime. With this advantage, the Federation/Klingon/Romulan fleet invaded the Cardassia System. However, Odo cured the Female Changeling of her disease and convinced her to order the Jem’Hadar and Breen to stand down. The war ended with the Dominion's surrender and the signing of the Treaty of Bajor.