In 2372 Chancellor Gowron withdrew the Klingon Empire from the Khitomer Accords after the Federation opposed his invasion of Cardassia.
The Khitomer Accords had kept the Federation and the Klingon Empire at peace for about eighty years. When the Federation condemned the Klingon invasion of Cardassia in 2372 and helped the Detapa Council escape, Gowron withdrew from the treaty. Klingon and Federation forces clashed along the border, and Gowron stripped the House of Mogh of its lands and Council seat after Worf sided with Sisko.
The split lasted about a year. After Cardassia joined the Dominion in 2373, Gowron restored the Accords, and the Klingons and the Federation became allies again in the coming war.