Stardate 47529.4: Doctor Bashir and Chief O'Brien board a ship above a planet whose populace had been wiped out by a genetic bioweapon, called Harvesters, to help to destroy the bioweapon used for a centuries long war. After many failures, the Kellerun and T'Lani, with the help of the DS9 crewman, are able to find the right radiation array that will destroy the weapon. Tragically, just as the last Harvesters are put in the radiation chamber to be destroyed, armed soldiers burst in and open fire. Bashir and O'Brien are able to fend off their attackers, but with more on the way their only option is to beam down to the planet's surface.
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.