In late-2372, the Klingon chancellor, Gowron demanded the the Federation abandon its military bases within the sector and hand it back to the Klingon Empire despite the empire surrendering its claim in the 23rd century. He later sent a task force to reclaim the sector, giving the Federation ten days to evacuate. When the Federation did not it resulted in the beginning of a war between the two.
When the Klingons broke the ceasefire in early 2373 the Klingon Defence Force Second and Sixth battle groups drove the Starfleet's Eleventh Fleet from its positions within the sector. When the ceasefire was reinstated the two sides returned to their original positions.