In 2373 Sisko laid a cloaked, self-replicating minefield at the mouth of the Bajoran wormhole to block Dominion reinforcements, starting the Dominion War.
By 2373 Dominion convoys were bringing more ships and soldiers through the wormhole each week. Sisko decided to block them with a minefield. Rom adapted the mines to cloak and replicate themselves, so that any mine destroyed would be replaced, making the field almost impossible to clear.
As the minefield was being laid, a Dominion and Cardassian fleet attacked Deep Space Nine. Sisko held the station long enough for the field to be completed, then evacuated Starfleet personnel and withdrew. Dukat's forces took the station, but the minefield cut them off from the Gamma Quadrant.
The minefield marked the start of the Dominion War. Rom stayed behind on the station, and the Dominion worked for months to take the mines down. Their attempt to do so led to Operation Return, during which the Prophets stopped the Jem'Hadar reinforcements inside the wormhole.