A disastrous early engagement of the Dominion War in which Starfleet's Seventh Fleet was all but wiped out, with only fourteen of its one hundred and twelve ships surviving the encounter.
The Battle of Tyra was one of the worst Federation defeats of the Dominion War. It took place in the Tyra system roughly three months after the Dominion seized Deep Space 9, when the Seventh Fleet met Dominion and Cardassian forces and was shattered.
The battle is not shown on screen. News of it reaches Captain Sisko and the crew of the Defiant in the Deep Space Nine episode A Time to Stand, where the figure of fourteen survivors out of one hundred and twelve ships brings home how badly the war is going.
The loss deepens the gloom in Starfleet and helps to push the admiralty towards riskier plans, including the covert strike on the Dominion's ketracel-white stores that Sisko's crew carries out in a captured Jem'Hadar ship.