The Archanis sector was a sector of space claimed by the Klingon Empire and United Federation of Planets. Archanis IV is the most important planet in the sector.
The Archanis sector was controlled by the Klingons until the late 23rd century. In 2372, Gowron demanded that the Federation to withdraw from the sector and later sent a task force to the sector, giving Starfleet just ten days to evacuate the sector. (DS9 episode: "Broken Link")
Archanis was taken over by the Klingons soon after, although Starfleet launched an counter-attack several months later. (DS9 episodes: "Apocalypse Rising", "Nor the Battle to the Strong")
In an alternate timeline, Admiral Thelin led a series of succesful campaigns against the Klingon Empire during the Genesis War. (Star Trek: Myriad Universes novel: The Chimes at Midnight)