Sometime before the events of the series, Jarre was conquered by the Galra Empire. It was ruled by a viceroy who administered the government and had his own guard, while swearing fealty to the Galran emperor. 
Jarre was liberated by Golion and its team in 1999. In the process, the incumbent viceroy was slain by Sadak.
A few months later, Prince Imperial Sincline made an attempt to retake Jarre and destroy Golion, using a duplicate of Golion. The attempt failed, and the duplicate Golion was destroyed.