In 2372 the Klingon Empire invaded the Cardassian Union, claiming its new civilian government had been taken over by Changelings.
In 2372 a civilian uprising removed the Cardassian Central Command and gave power to the Detapa Council. Chancellor Gowron, encouraged by General Martok, claimed that the new government was controlled by the Founders and launched a full invasion of Cardassian space. The Federation condemned the attack.
Sisko, with Garak and Gul Dukat, rescued the members of the Detapa Council and brought them to Deep Space Nine. Gowron then attacked the station, but backed down after a fierce battle. In response to Federation opposition, he withdrew the Empire from the Khitomer Accords, and the Klingons held on to the Cardassian worlds they had seized.
The war continued through 2373 and badly weakened both powers, which suited the Dominion. It was later revealed that Martok had been replaced by a Changeling, who had urged the invasion to set the Alpha Quadrant powers against one another. The fighting ended when Cardassia joined the Dominion and Jem'Hadar forces drove the Klingons out of Cardassian space.