Battle of Cardassia
The Battle of Cardassia was the final battle of the Dominion War, fought in late 2375. The Federation Alliance, the forces of the United Federation of Planets, the Klingon Empire, and the Romulan Star Empire, launched an invasion of the Dominion-held Cardassian Union, with the goal of capturing the Dominion's capital on Cardassia Prime. The battle would ultimately lead to the Dominion's unconditional surrender of all forces in the Alpha Quadrant.
By late 2375, the Dominion's offensives into the Alpha Quadrant had been stalled along multiple fronts. With the Bajoran wormhole effectively closed to Jem'Hadar reinforcements and Cardassian resources strained to their limits, the Founders sought to withdraw back into the safety of Cardassian space and establish a strong defensive line until the situation improved. Even the initial benefits of aligning themselves with the Breen Confederacy---that being their surprise energy-dampening weapons used so effectively at the Second Battle of Chin'toka---had been nullified by modifications to Federation and Romulan ships. The chance to strike at the Alliance while only the Klingon Defense Force held the line was thwarted by Cardassian uprisings led by Legate Damar, which forced the Dominion to commit vital forces to quell the rebellion.
Admiral William Ross and Captain Benjamin Sisko of Starfleet and Chancellor Martok agreed that allowing the Dominion to entrench in in the quadrant was dangerous and would allow their reeling forces time to recover. Their plan was to take the fight to the heart of the Dominion---Cardassia Prime.
The Alliance fleet launches from Deep Space 9 and travels a day and half into Cardassian space. The Dominion musters every available ship to counter the attack, believing this to be the determining battle as to who will win the war. As the attack unfolds, Damar has his rebels launch an assault on the Dominion's command and control installations and communication systems. This succeeds in blinding the female Changeling and her staff the the battle. She orders immediate and brutual reprisals launched against Lakarian City and the resulting bombing claims 2 million Cardassian lives.
Meanwhile, the space battle reaches a fever pitch. The Alliance ships manage to weaken the Dominion center, but the Romulans take a severe beating on one of the flanks. This forces Adm. Ross and Capt. Sisko to divert their limited reserves to assist their allies. Without commands from Cardassia Prime, the Dominion movements are uncoordinated and at times suicidal...but effective. Their ships begin to press hard on the Alliance flanks, threatening to overrun the line. Plans are made to pull the fleet back to Federation space, when both sides get a major surprise: the Cardassian ships begin to fire on their Dominion allies. News about Lakarian City as reached them, and they quickly switch sides. Despite losing 33% of its forces, the Alliance pushes its advantage and breaks through the center of the Dominion line, headed for Cardassia Prime.
Once communications are restored, the Changeling learns of the Cardassian betrayal. She orders all Dominion ships back to the planet and sends the Jem'Hadar to annihilate the civilian population. Over a thousand ships and orbital defense platforms await the Alliance fleet at Cardassia Prime. The Changeling issues orders to fight to the last man, planning to make any Alliance victory a Pyrrhic one. By inflicting such a terrible loss here, she believes that it will take years for the Alliance to recover and invade the Gamma Quadrant. Determined to rid their part of the galaxy of the Dominion threat, Ross, Sisko, and Martok agreed to a three-pronged attack. Before it is launched however, Odo cures his fellow Changeling of the deadly morphogenic virus and convinces her to surrender.
The Dominion signs the Treaty of Bajor, ending the war and forcing all their forces back to the Gamma Quadrant. The Breen give up all claims to conquered worlds and return to their space as well. Alliance forces occupy the Cardassian Union and begin assisting in recovery efforts. All told some 80 million civilians are killed in the genocide by Jem'Hadar troops. The female Changeling is charged with war crimes and imprisoned.