A star system where Starfleet's Seventh Fleet was all but annihilated by the Dominion early in the war, with only fourteen of its one hundred and twelve ships surviving.
The Tyra system is the scene of one of the Federation's worst defeats in the opening months of the Dominion War. Starfleet's Seventh Fleet is sent there in an attempt to halt the Dominion advance.
The battle is not shown. In the Deep Space Nine episode A Time to Stand, the crew of the USS Defiant, retreating with a battered task force, learns that only fourteen of the fleet's one hundred and twelve ships made it back.
The news deepens the gloom that hangs over the start of the sixth season, with Deep Space 9 in enemy hands and the Federation Alliance in retreat. It helps to explain why Starfleet turns to riskier ventures, such as Sisko's raid on a ketracel-white facility in a captured Jem'Hadar ship.