The Allied fleet engages the Dominion.
Dominion forces in orbit of Cardassia
The Battle of Cardassia was the final battle of the Dominion War, fought in late 2375. The Federation Alliance (the United Federation of Planets, the Klingon Empire, and the Romulan Alliance) launched an invasion of the Dominion-held Cardassian Union, with the goal of capturing the Dominion's capital in the Alpha Quadrant. The battle would ultimately lead to the Dominion's unconditional surrender of all forces in the Alpha Quadrant.
Once the Allied ships had developed effective countermeasures to the Breen energy-dampening weapon, the Founders ordered the Dominion forces to effect a complete withdrawal from all territories held inside the Federation Alliance. It was hoped that by reverting to antebellum territories, the Dominion would be able to build up a defense perimeter, shorten its supply lines, and survive longer.
Launching their attack fleet from Deep Space Nine, the Allied Fleet, perhaps the largest ever, set a course for Cardassia. The Female Changeling ordered as many ships as possible to meet them, perceiving the nearing endgame of the war.
As the two enemy fleets made their final approach, the Female Changeling, the Vorta Weyoun, and Breen Thot Pran were inside Dominion Headquarters making final plans for the attack. Suddenly, nearly every Dominion installation on the surface of the planet lost power - The Cardassian Rebellion under the leadership of Legate Damar had dealt a serious blow. Legate Damar had inspired the Cardassian populace to rise up and overthrow their Dominion occupiers. The Dominion was completely cut off from the Cardassian surface.
In orbit, the two fleet bore into each other with ferocity. Soon the battle became chaotic with close-quarter combat between the swift Starfleet and Breen ships and the heavier Dominion, Klingon, and Romulan forces. Although its lines were thin, especially in the middle, the Dominion managed to exact a heavy toll on the Romulan lines, destroying the Romulan flagship. Captain Sisko brought several attack wings to reinforce the Romulan lines, while Admiral Ross and Chancellor Martok's forces targeted the Dominion center.
On Cardassia, with communications restored and with the information that the Cardassians had turned on them, the Jem'Hadar was let loose on the Cardassian populace. The Female Changeling ordered the destruction of Lakarian City, a city of two million. Weyoun announced to the public that another Cardassian city would be destroyed for each further act of sabotage.
In space, the allied lines were stretched thin and lines were crumbling on the flanks from Dominion attack. The allied fleet was preparing to retreat when the Cardassian ships shifted sides and began attacking the Dominion ships, in response to the destruction of Lakarian City. Taking advantage of the situation, the allied forces rallied for an attack on the Dominion's center, punching into the core of the defending fleet.
Furious, the Female Changeling ordered the Dominion and Breen forces to disengage and retreat closer to Cardassia Prime.
The battle was not yet over, however. Captain Sisko convinced Chancellor Martok and Admiral Ross to press their advantage, despite having already lost an astounding 30% of their forces. Even with the Dominion bottled up in the Cardassian system, their ability to replace lost ships and troops proved too dangerous to permit. The Allies chose to press ahead.
With the Jem'Hadar out killing every Cardassian they could find, Damar - along with Kira Nerys, Elim Garak, and a handful of volunteers, mounted a daring assault of Dominion Headquarters, seeking the Female Changeling. Although Damar was killed during the final assault, most of the remaining rebels fought their way to the headquarters' briefing room, capturing the Female Changeling and Weyoun.
In orbit, the Allies saw a formidable opponent facing them in Cardassian orbit. Thousands of Jem'Hadar and Breen ship along with a multitude of Cardassian orbital weapons platforms were powered and waiting for the Allied fleet. Unwilling to turn back, they prepared to launch a three-prong attack on the Dominion's defenses. Federation vessels would attack the platforms, the Klingons and the Cardassians would hit the Dominion forces while the Romulans would take on the Breen - an attack that was projected to cost up to 40% of their remaining forces, even without the ground assault.
Although the Female Changeling was perfectly willing to allow the Jem'Hadar to fight to the last man, Odo - recently cured of the Founders' disease - volunteered to try to convince her to surrender to the allies. By linking with her, Odo managed to cure her of the disease and persuade her to call for an end to the fighting. The battle - and the war - were over.
The instrument of surrender, the Treaty of Bajor, was signed at Deep Space Nine only days later. In it, the Dominion agreed to withdraw all of its forces to the Gamma Quadrant, and the Cardassian Union was occupied by Federation Alliance forces.
The battle was nothing short of devastating for Cardassia, decimating a huge portion of its surface and killing over 800 million civilians. Hundreds of allied warships were lost at the cost of tens of thousands of lives. It was only in avoiding the final assault on Cardassia itself that more bloodshed was avoided.