The Pentath system was a planetary system in the Cardassian Union. A planet in this system, Pentath III, was a Cardassian world. This world remained in Cardassian hands during the Klingon-Cardassian War, but it bordered territory the Klingon Empire had seized.
The Detapa Council dispatched several relief convoys to the system in 2372 in response to an outbreak of Rudellian plague, though it lacked the warships to defend them against Klingon raids. Instead, the convoys were escorted by Federation starships, including the USS Defiant.
During the mission, the Klingons attempted to stop the Federation from further escorting Cardassian convoys by framing Lieutenant Commander Worf, who was commanding the Defiant, for a war crime. In a battle, an unmanned Klingon transport decloaked in front of the Defiant and was inadvertently destroyed. Subsequently, the Klingon Empire attempted to have Worf extradited for the "massacre" of the non-existent civilians aboard. (DS9: "Rules of Engagement")