The Terran Empire was the opressive interstellar government dominated by the Terrans from Terra in the mirror universe. The Empire ruled by terror, with its Imperial Starfleet acting as its iron fist. In Starfleet, officers promoted themselves by killing superiors that did not follow the rules of the Empire. Torture was a common form of interrogation. The Empire was the counterpart of the prime universe United Earth and the United Federation of Planets governments.
After the defeat of the Alliance and gaining back they're freedom; Terran rose back to power, but with Smiley O'Brien as Leader of the new Galactic Commonwealth. The goal was keep the peace in the galaxy and refrain from returning to their old, brutal days of spreading terror. His son James O'Brien and a group terrans including; Captain Mercury, Vice Admiral Solarmetric still believed that terror is still way to keep order in the galaxy. James O'Brian assassinated Smiley and took his place as Emperor and brought back the Terran Empire as a super power in the quadrant.
In early 2415 during the final events of the War of the Universes. Desiree Mendroza took over as Empress of the Terran Empire and issued major reforms. Unlike before when Spock made reforms with no allies. The Empire now had the Interspecies Republic providing protection and support from the United Federation of Planets. The Reformed Terran Empire worked more like the Federation and the Galactic Commonwealth. Every planet and species of the old Terran Empire were now liberated and were receiving relief supplies and rebuilding service.
Loyalist and reformist
During the events of War of the Universes, it was discovered that there was dissent in the ranks of the Empire.
Imperial officers who support the ideas of Smiley O'Brien's peaceful solution were known as reformists. Imperial officers who supported the ideas of James O'Brien's oppressive and terror solution were known as loyalists.
Even though hidden with the ranks the reformist were great in number more so than loyalist. Due to fear, the reformist continued to do the bidding of the empire. It was L'Tema that help gather the reformist, and when the time was right. They risen from the darkness and claimed the Empire.
- Terran Empire at Memory Alpha, the Star Trek wiki
- Terran Empire at Memory Beta, the non-canon Star Trek wiki
- Terran Empire at the Star Trek Online Wiki