Region along the Federation-Cardassian border created by treaty, where settlers on both sides clashed and the Maquis movement was born.
The Demilitarized Zone is the strip of territory along the Federation-Cardassian border established by the treaty that ended their war. Federation colonies left on the Cardassian side and Cardassian settlements nearby are meant to coexist without military forces, but in The Maquis, Part II and its first part, tensions spill over into open violence.
Starfleet's attaché Calvin Hudson comes to believe the Federation has abandoned its colonists, and settlers take up arms as the Maquis, while the Cardassians secretly arm their own colonists. The region becomes the center of the Maquis rebellion.