With the unpleasant introduction of the Dominion to the Federation, the Alpha Quadrant begins to worry about a possible invasion from their neighbors in the Gamma Quadrant. Major Kira has run countless simulations on a possible attack and Deep Space Nine is always shown to be vulnerable. As Ops meets to discuss the matter further, a cloaked ship appears almost within the range of the station's shields. As the crew watches the ship uncloak, they notice that it bears the nomenclature of a Starfleet ship. Commander Benjamin Sisko hails the station from the vessel, introducing his staff to the USS Defiant. Armed with the latest Federation vessel, the crew of Deep Space Nine head into the Gamma Quadrant to find the Dominion's leaders, known only as the Founders.
When the Cardassian occupation of Bajor ended in 2369, the mining space station Terok Nor was left abandoned, its systems ripped out. By invitation of the Bajoran provisional government, Starfleet stepped in to oversee the rebuilding and day-to-day operations of the newly christened Deep Space Nine.
The years of Starfleet's nonintervention into Cardassian matters, however, had taken its toll on relations with the Bajorans. Consequently, Starfleet's position was a tenuous one; many Bajorans, suspicious and hostile as a result of decades of Cardassian oppression and brutality, did not greet the Federation's presence with open arms. The Federation's assistance is put to the test as DS9 becomes a center of travel and commerce that stretches into the Gamma Quadrant.