Earth in the mirror universe was the center and capital of the Terran Empire, with a history different from the primary universe's Earth. One historical difference arose in 2063, when Zefram Cochrane made first contact with the Vulcans. His colleagues attacked the Vulcans and stole their technology. (ENT: "In a Mirror, Darkly") The Terran Empire was in existence for centuries by 2155. ("In a Mirror, Darkly") The Klingon-Cardassian Alliance conquered the Empire sometime prior to 2370. (DS9: "Crossover")