The 2371 Cardassian coup d'etat occurred in the wake of the near-annihilation of the Cardassian Obsidian Order by Dominion forces in the Gamma Quadrant. The coup was initiated by the leaders of the Cardassian dissident movement, a group of elite civilians who resented military rule and wished for power to be transferred to the Detapa Council. (DS9 episode: "The Way of the Warrior", DS9 novel: The Never-Ending Sacrifice)
With the elimination of the Obsidian Order, the dissidents moved quickly. Over the course of four days, through a combination of bribery, blackmail, and the assassinations of a Central Command legate and three guls, the dissidents secured the loyalty of the leaders of the various city constabularies on Cardassia Prime, while Alon Ghemor brought what remained of the Obsidian Order (now renamed the Cardassian Intelligence Bureau) to the table.
On the fifth day of the coup, the Detapa Council issued a Declaration of the Transference and Assumption of Powers, granting the Council all legislative and executive powers and stripping the Central Command of such powers entirely. The Central Command members were pressured to sign the Declaration, and all eventually did.
Once the coup ended, the new dissident government included Kotan Pa'Dar, who served as Cardassian Minister of Science; Erek Rhemet; Ithas Bamarek, chief commissioner of the constabularies; Alon Ghemor, head of the Cardassian Intelligence Bureau; and Meya Rejal, the new Chief Executor of the Detapa Council and Cardassia's new head of state. (DS9 novel: The Never-Ending Sacrifice)
By early 2372, Klingon Chancellor Gowron, son of M'Rel, had come to believe that the coup was instituted by the Founders of the Dominion, and ordered an invasion of the Cardassian Union. The Rejal government was saved by Gul Skrain Dukat, who relocated them to Federation Starbase Deep Space 9, which later fought off the Klingon invasion, indirectly inciting the Federation-Klingon War of 2372-2373. The Rejal government found itself fighting a prolonged war with the Klingons thereafter. (DS9 episode: "The Way of the Warrior")
The Rejal government later proved largely ineffectual, corrupt, and unpopular, and was overthrown in the 2373 coup by Gul Skrain Dukat and his allies in the Dominion. (DS9 novel: The Never-Ending Sacrifice)