| CONFLICT | |
| Terran-Klingon War | |
 A Klingon bird of prey fires a photon torpedo | |
| Belligerents: | Terran Empire vs. Klingon Empire |
| Date(s): | 2242-2294 |
| Location(s): | Alpha Quadrant |
| Scale: | Full-scale declared war |
| Result: | Terran victory, Klingons become slaves to the Terran Empire, and the destruction of Qo'noS |
| Casualties: | many Terran starships, many Klingon starships |
In the dark mirror universe, the Terran-Klingon War was a conflict between the Terran Empire and the Klingon Empire from 2242 to 2294, which brought the end of the Klingon Empire after the destruction of Qo'noS as well as other Klingon colonies, where a fleet of Imperial Starfleet vessels led by Fleet Admiral James T. Kirk, and the rest of the Klingons became slaves of the Terran Empire.
The war[]
In the mid 2260s, Imperial Starfleet were able to install modified cloaking devices on their vessels which allows them to fire on any enemy vessels while cloaked, and improved their weapon systems.