When the Dominion ships used to emerge from the wormhole without DS9 realizing it, all they saw was the wormhole opening and closing without reason.
That never actually happened. The opening and closing of the wormhole was due to a device placed near the communications relay on the wormhole's far side, giving the appearance
that a cloaked fleet was coming through. Sisko managed to even find the officer responsible and had Kira put him on the Defiant
before they came to Earth to help him stop Admiral Leyton.