In 2370 the Jem'Hadar destroyed the Galaxy-class USS Odyssey in the Gamma Quadrant, giving the Federation its first clear sign of the Dominion's power.
In 2370 Sisko, his son Jake, Quark and Nog were captured by Jem'Hadar soldiers in the Gamma Quadrant. The Jem'Hadar declared that the Dominion would no longer allow outsiders to pass through the wormhole and revealed that the Bajoran colony of New Bajor had already been destroyed.
The USS Odyssey was sent with two runabouts to rescue the prisoners. During the escape, a Jem'Hadar ship rammed the Odyssey and destroyed it. The Vorta Eris, who had posed as a fellow prisoner, turned out to be a Dominion agent.