Second Battle of Deep Space 9
The Second Battle of Deep Space 9 was the opening engagement of the Dominion War between the United Federation of Planets and Klingon Empire against the combined forces of the Dominion, under the nominal command of Gul Dukat, were able to capture Federation starbase Deep Space 9. 

Fought in 2373, the assault was launched by the Dominion to prevent the mining of the Bajoran wormhole, which would effectively sever supply lines from the Gamma Quadrant. Two days after Captain Benjamin Sisko rejected Weyoun's ultimatum to remove the minefield, a large fleet of Jem'Hadar and Cardassian warships launched an assault on the station, intending to capture it before the  could complete the minefield. 

Although the Dominion successfully captured the station from the Federation and drove Federation-Klingon forces from Bajoran space, the losses they incurred were severe; fifty ships were destroyed in the battle, and the Dominion was unable to prevent the activation of the minefield.

Prelude 
Following their annexation of the Cardassian Union around Stardate 50560, the Dominion began fortifying their foothold in the Alpha Quadrant with weekly convoys of warships and troops through the wormhole. As time went on, Cardassian space became a veritable fortress, teeming with Jem'Hadar soldiers and their Vorta overseers. ()

Although a technical state of war did not exist, and neither side had fully committed to immediate combat, numerous skirmishes took place along the border during this period. Aside from the Dominion's attempt to destroy the Bajoran system using a trilithium bomb, the Jem'Hadar and the Cardassians attacked and destroyed numerous Federation and Klingon patrol ships in a sustained campaign across the border sectors. Casualties of these attacks included the  and the . ()

In addition to the military advances, the Dominion made major inroads into the Alpha Quadrant politically as well, signing nonaggression pacts with several regional powers, including the Miradorn and the Tholian Assembly, and offering similar pacts to Bajor and other independent worlds in the area. The Dominion's greatest diplomatic achievement, however, was the signing of a nonaggression pact with the Romulan Star Empire, the third major power in the region. The Dominion's goal seemed clear: to isolate the Federation politically and militarily. Its classic strategy of divide-and-conquer seemed to be succeeding admirably. Only the Klingon Empire stood with the Federation against the Dominion. With peaceful means failing to slow the Dominion's advance, Benjamin Sisko observed, "...a war may be our only hope." ()

Provocation 

With its strategic position rapidly deteriorating, the Federation resolved to prevent the Dominion from sending further reinforcements into the Alpha Quadrant by mining the entrance to the Bajoran wormhole. Maintenance engineer Rom suggested using self-replicating mines equipped with cloaking devices for the blockade; not only would such a minefield be undetectable to approaching ships, but it would also be virtually indestructible, as each mine destroyed would be replaced by another mine in the vicinity. Chief Miles O'Brien and Lieutenant Commander Jadzia Dax quickly developed a working model, and the Defiant began laying down the minefield.

This action could be seen as nothing less than a major provocation, however, and the Dominion's primary representative Weyoun arrived at Deep Space 9 and promptly demanded that the mining of the wormhole be halted immediately. Captain Sisko flatly refused.

An intricate dance of lies and intimations began: Weyoun claimed that the Cardassians, having suffered terrible damage during the Klingon-Cardassian War, required massive assistance in rebuilding their infrastructure and defenses following the Klingon invasion. Sisko played along, claiming to have had no idea of the Cardassians' dire humanitarian situation. The two representatives arranged a deal, in which the Federation would remove the minefield, and the Dominion would restrict further convoys to nonmilitary personnel and materials. However, both sides recognized this repartee as nothing more than a ruse to buy time and lull the other side into a false sense of security – Weyoun to prepare the Dominion fleet for the attack, and Sisko to complete the minefield.

With war imminent, Sisko, speaking both as a Starfleet captain and the Emissary of the Prophets, advised that the Bajoran government sign the nonaggression pact offered to them by the Dominion, thus ensuring that the planet and its people were kept out of the now-inevitable conflict. The pact was signed, and First Minister Shakaar Edon ordered the evacuation of all Bajoran personnel from the station. ()

The Battle 

Intent on preventing its lifeline to the Gamma Quadrant from being blocked, the Dominion and Cardassian Union launched a massive assault fleet towards Deep Space 9, with Gul Dukat himself in command. For reasons not yet publicly known, the Federation had not reinforced its position at Deep Space 9, leaving only the USS Defiant and the  to supplement the station's defenses. Anticipating the enemy attack, Sisko ordered the Rotarran to patrol the border and provide advance warning when the Dominion fleet approached.

Captain Sisko confidently rejected Dukat's offer to surrender, and both sides prepared for the onslaught. Dukat ordered five Jem'Hadar attack wings to intercept the Defiant, while his remaining ships targeted the station.

As the Dominion fleet opened fire, Weyoun and Dukat were unpleasantly surprised to find Deep Space 9's shields holding up under the barrage – Federation deflector shields had previously been impotent in defending against the Jem'Hadar's phased polaron beam weaponry. Dukat ordered more ships to open fire on the station. 

Meanwhile, the Defiant herself was coming under fire as she was laying the minefield. The Rotarran provided interference and covering fire, giving the Defiant enough time to complete and activate the minefield, sealing off the wormhole.

Using his knowledge as the station's former commanding officer, Dukat was able to cut main power to Deep Space 9's shields by directing all Dominion and Cardassian firepower into Section 17 of the outer docking ring. With the wormhole now blocked, and the station becoming an impossible position to hold, Captain Sisko ordered all Starfleet personnel to evacuate Deep Space 9. As Dukat ordered his reserve units to enter the battle, the station's Starfleet crew boarded the Defiant and the Rotarran, taking all sensitive equipment with them and leaving the station in the hands of the Bajoran Militia. 

As the evacuation neared completion, Sisko addressed the remaining station residents on the Promenade, promising, "I will not rest until I stand with you again, here, in this place where I belong." 

Once the Defiant and the Rotarran had safely departed the station, Major Kira Nerys, now the Bajorans' representative to the Dominion, activated Program Sisko 197. The program completely sabotaged the station's computer and power systems, leaving the station a nearly lifeless hulk. The Dominion and Cardassian troops boarded the station without resistance, officially reclaiming Terok Nor, the station they had abandoned in orbit of Bajor five years before. ()

Aftermath 

Dukat and the Dominion captured Deep Space 9 from the Federation, but the more than fifty Dominion ships destroyed were a major price to be paid for that victory. The minefield operated independently from the station and proved resistant to all initial attempts to dismantle it. Likewise, the sabotage of the station itself meant that in the short term it would serve little function other than as a command and supply outpost behind the front lines.

In addition, while the Dominion and Cardassian Union had thrown its full force towards capturing the station, a combined Starfleet-Klingon task force had crossed the border into Cardassian territory and destroyed the shipyards at Torros III, which in the eyes of Starfleet Command outweighed the loss of DS9. ()

bg:Втора битка за Дълбок космос 9
cs:Druhá bitva o Deep Space 9
de:Schlacht von Deep Space 9 (2373)
fr:Seconde Bataille de Deep Space Nine
ja:第二次ディープ・スペース・９の戦い
nl:Tweede slag om Deep Space 9
Deep Space 9, Second Battle of