In "A Time to Stand" (S5E26) Starfleet mines the entrance to the wormhole, starting the Dominion War. No reinforcements are sent to defend Deep Space Nine so the fleet can destroy Dominion shipyards, and the Defiant is busy deploying the minefield. Once the minefield is activated, the Defiant and the Rotarran evacuate the remaining personnel on DS9 and leave under cloak to join the fleet.
However, what happened to runabouts that were stationed there? We don't see them leave, or attempt to defend the station (admittedly it's doubtful they could help defend against a fleet, but they were deployed alongside the Defiant for defence during "By Inferno's Light" (S5E15) so it's not unprecedented). We also know that the runabouts survive as we see them after the station is retaken (at least, we know that the seemingly indestructible Rio Grande survives - why anyone ever chooses to use a different runabout is beyond me!).