Tyra system

The Tyra system was a star system held by the Dominion during the Dominion War. During the first few months of the war, the Federation and Klingon forces were suffering staggering defeats consistently. With the Dominion pushing deeper into Federation territory, the Seventh Fleet was dispatched to the Tyra system in an attempt to prevent the Dominion from moving further into their space. Comprised of 112 vessels, the Federation was confident the fleet would be successful at Tyra. However, the fleet was defeated and suffered incredible losses; only 14 ships made it back to Federation territory. The battle badly damaged the allies’ morale. 

Kagan, a hologram in a Section 31 holoprogram, claimed to have been with the Seventh Fleet at Tyra, where he said he had lost a lot of friends. Julian Bashir also knew several people who were killed in the Tyra system.