With the loss of Deep Space Nine to the Dominion, the Federation-Klingon alliance was placed in an increasingly precarious position. Although the entrance to the wormhole was mined, the Dominion was known to be working on methods to clear the obstruction and bring heavy reinforcements through from the Gamma Quadrant - a move that would surely make the war unwinnable.
Captain Sisko developed a plan to attack and recapture Deep Space Nine using elements from several Federation fleets bolstered by a contingent of Klingon ships. These forces began to gather at Starbase 375 in preparation for the attack, but word was recieved from Deep Space Nine that the Cardassians had in fact discovered a method of disabling the minefield. Starfleet had only six hundred ships ready to go, while the Klingons had not yet committed any forces to the plan. Nevertheless, faced with the imminent arrival of Dominion forces from the Gamma Quadrant, Captain Sisko took what forces he had to hand and headed for Deep Space Nine.
Unfortunately, the Federation fleet was intercepted on route by a Dominion fleet of over twleve hundred ships. Outnumbered two to one, the deadline set by the events at Deep Space Nine forced Captain Sisko to attack the Dominion fleet head on in an attempt to get whatever forces he could to the station before the minefield fell. 
Initially the Federation forces concentrated their attacks on the Cardassians, hoping to split them from the Jem'Hadar and divide the enemy. In the event the Dominion fleet offered such an opening only as a trap; nevertheless Captain Sisko threw every ship he had into the breach in an all out assault. The attack rapidly disintergrated into chaos; the Dominion pressed home their numerical advantage, inflicting massive losses on the Starfleet forces.
The Federation fleet was beginning to crumble when the Klingons finally arrived; catching the Dominion unawares, a large fleet under General Martok smashed into the enemy flank. The Defiant used this oppurtunity to blast her way through the fleet and headed for Deep Space Nine at maximum warp speed.
The Defiant arrived at Deep Space Nine just in time to see the minefield detonated by the Cardassians; Captain Sisko took his ship into the wormhole to try and at least hold up the Dominion reinforcements. At this point the wormhole aliens intervened, apparently curious about Siskos motivations. The Captain convinced the aliens to intervene in the war, and they deleted the oncoming fleet shortly before it reached the alpha quadrant.
The Defiant emerged from the wormhole to learn that the Federation-Klingon fleet had won a stunning victory over the Dominion, forcing them into retreat. Faced with a mass assault on the station which would endanger the life of a Founder, the Dominion evacuated the station and pulled its forces back to Cardassian space. Gul Dukat, the Cardassian leader, became mentally unbalanced at the magnitude of his defeat and was left behind on the station. Captain Sisko won a bet by setting foot on Deep Space Nine's promenade a full ten seconds before General Martok, to a rapturous welcome from the Bajorans.