In the mirror universe, the Cardassian Union was an interstellar political entity controlling Cardassia and its territories. For much of the 24th century, it was one of the two dominant powers in the Alpha Quadrant as part of the Klingon-Cardassian Alliance.
The Cardassians were a generally militaristic race. In the late 2270s, the Cardassian Union was engaged in numerous border conflicts with the Tholian Assembly. At Emperor Spock's order, the Terran Empire provided ships and small arms to the Cardassians in order to aid them in their wars against the Tholians.
By the early 2290s, the Cardassian Union, then led by Legate Renar, was an emerging power in the Alpha Quadrant which sought to increase its scope at the expense of the Terran, Klingon and Romulan Empires.
In 2293, Renar represented his people at the Khitomer Conference, a diplomatic conference held by the major Alpha Quadrant powers on the Klingon-held world Khitomer following the explosion of Praxis, one of the moons of the Klingon homeworld Qo'noS. While both his Klingon and Romulan counterparts offered Emperor Spock the opportunity to enter into an alliance with their respective empires at the conference, the Cardassians were more pragmatic as they were aware that they had comparatively little to offer the Terran Empire in comparison to the Klingons and the Romulans. Instead, they sought to extend their influence over the territory of the Terran Empire in a more direct manner.
Following the failure of the Khitomer Conference, Spock postulated that the Cardassians and the Klingons would meet to discuss a grand alliance between the Cardassian Union and the Klingon Empire, which would allow them to defeat the Terran Empire. This prediction was proven entirely correct. In 2295, the Klingon-Cardassian Alliance was formed. In a relatively short period of time, the Alliance was able to completely defeat the Terran Republic, the short-lived successor state of the Terran Empire, using an advanced fleet of Klingon birds-of-prey which had the ability to fire their weapons while cloaked. The Terrans, the Vulcans and other former subject species of the Terran Empire were massacred while the survivors were enslaved. (TOS - Mirror Universe novel: The Sorrows of Empire)
The Alliance remained the undisputed major power in the Alpha Quadrant until the early 2370s, at which time its stability was threatened by the success of the Terran Rebellion. (DS9 episodes: "Crossover", "Through the Looking Glass", "Shattered Mirror", "The Emperor's New Cloak")
In January 2379, the Terran Rebellion, with the assistance of Memory Omega and M'k'n'zy of Calhoun, was victorious in its war against the Alliance. The Terrans, the Vulcans and the other enslaved species were freed and the Galactic Commonwealth was founded. A neutral zone was subsequently established between Alliance and Commonwealth space. This effectively ended the unprecedented power and influence over galactic affairs which the Cardassian people had enjoyed for the previous 86 years as one of the two principle races in the Alliance. In 2380, the Alliance was officially dissolved. (ST - Mirror Universe novel: Rise Like Lions)
|States in the mirror universe|
|treaty of alliance and mutual defense||Galactic Commonwealth • Romulan Star Empire|
|Taurus Pact||Breen Confederacy • Gorn Hegemony • Tholian Assembly • Tzenkethi Coalition|
|non-aligned states||Borg Collective • Cardassian Union • Dominion • Ferengi Alliance • Grigari • Kazon-Ogla • Kinshaya • Klingon Empire • Talarian Republic • Thallonian Empire|
|defunct states||Klingon-Cardassian Alliance • Terran Empire • Terran Republic • Terran Rebellion • Terran Protectorate|