Corulag was first colonized by Humans from Coruscant. This led to thousands of years of the residents complaining that it wasn't as nice as Coruscant. Actually, it was much nicer than Coruscant, because it had not been severely over-developed yet. The Republic had an academy built there for the study of physics and engineering, but it eventually just evolved into a military school. Corulag remained closely allied with Coruscant, and was loyal to the Empire.