A planet in the Archanis sector that the Klingon Empire gave up a century earlier and which Gowron abruptly demands back in 2372, pushing the Federation and the Empire into open war.
Archanis IV lies in the Archanis sector, near the border between the Federation and the Klingon Empire. The Klingons had abandoned their claim to it about a hundred years before the Dominion crisis.
At the end of Broken Link, Chancellor Gowron broadcasts an ultimatum reviving that claim and ordering the Federation to withdraw from the planet and from every base in the sector, or face war. The demand leads directly to the fighting seen in Nor the Battle to the Strong and to the mission against Gowron in Apocalypse Rising.
The name goes back to the original series episode Day of the Dove, in which an alien entity makes Chekov believe that a brother of his was killed by Klingons at a research outpost on Archanis IV.