The Second Battle of Deep Space Nine, 2373
Although not as bloody as other conflicts on this list—and arguably a tactical victory for Starfleet—the beginning of the Dominion War’s transition into a hot conflict saw Starfleet and its Klingon allies successfully complete a blockade of the Bajoran Wormhole, activating a minefield around Deep Space Nine that essentially cut off Dominion supply lines to the Gamma Quadrant. In distracting the Dominion and Cardassians at DS9, Starfleet also bought time to launch an assault a Cardassian-Dominion shipyard at Torros III, striking a crucial opening blow in the early days of the war.
But all that came at a heavy cost: Deep Space Nine was re-occupied by the Cardassians and their Dominion allies, with all Starfleet personnel forced to abandon the station during the invasion. It was a huge blow to the morale of the Bajoran people, who found the lingering threat of Cardassia on their doorstep once more just five years after the end of their homeworld’s occupation, even if Starfleet and its allies would eventually retake the station.
