A series of battles between the Federation Alliance and the Dominion over a Cardassian system.
Chin'toka was a Cardassian system that the Dominion had fortified with a network of orbital weapons platforms, and it stood as a major obstacle to the allied advance during the Dominion War. Starfleet, Klingon and Romulan commanders agreed that taking it would open a path toward the Cardassian core worlds and relieve pressure on the Federation.
The assault was costly. The platforms were formidable and the defenders fought hard, but the allied fleet eventually destroyed them and captured the system. Captain Sisko and the crew of the Defiant took part in the fighting, and the victory was celebrated as the first genuine breakthrough in months.
The celebration did not last. While the battle was being won, Gul Dukat infiltrated Deep Space Nine and killed Jadzia Dax, and Sisko, shaken by the loss and by the Prophets' warnings, left the station. In the longer run Chin'toka showed how quickly gains could be reversed, since the Dominion soon gained a powerful new ally in the Breen and the allies found their hold on the system contested.