Dark Trooper Phase Zero project

The Dark Trooper Phase Zero project was a program run by then Lieutenant Rom Mohc of the Galactic Empire, to keep aging veteran clone troopers in the service by rebuilding them as cyborgs called Phase Zero Dark Troopers. The project was eventually shut down, but succeeded later by the Dark Trooper Project also headed by Rom Mohc.

The program was based on the Empirical, a hidden space station in the Dominus sector.

History
The Dark Trooper Phase Zero project was implemented by to deal with a shortage of experienced troops during the early years of the Empire. To return veterans of the Clone Wars to peak condition, their limbs and organs were removed and replaced with cybernetics using much of the same technology used to transform Darth Vader into a cyborg. In some case, over 70% of a clone's body was replaced. With their years of combat experience and cybernetic enhancements, the units that did make it onto the field were undeniably effective. However, as the subjects were forcibly recruited into the project, many Phase Zero Dark Troopers could not cope with the state of being more machine than man and attempted suicide. The project was eventually shutdown as the Empire grew in power and recruitment of non-clones improved greatly.

Behind the scenes
The Dark Trooper Phase Zero project could explain the appearance of cyborg dark troopers in Star Wars: Battlefront II, though Leland Chee, keeper of the Holocron Continuity Database, has already stated they should be considered as for gameplay purposes only.