The Imperial Republic was a powerful political entity that rose following the fall of Empress Talmerith Jael.
After the brilliant General Selkisto Horten overthrew the Empress Talmerith Jael, his People's Galactic Alliance ("PGA") had carte blanc to reshape the politics of the galactic core as they pleased. Leaving Coruscant to puppet Emperor Christopher Fel, the now Chancellor Selkisto moved the PGA Senate to Rhen Var.
Continuing his alliance with the powerful Velmoran Oligarchy, including Senator Tiffany Vandergraff, Chancellor Selkisto was in a position to dominate trade and politics all through the galactic core. With the backing of many powerful Senators, as well as the Coruscant Sector H-88 branch of the Intergalactic Banking Clan, the Imperial Republic was able to exert influence all the way from Bespin, Eriadu and Alzoc III along the lower Hydian, Taris and Dathomir on the Perlemian spur, and the entire Perlemian Trade Route from Coruscant to Mon Calamari.
The Imperial Republic was never able to satisfactorily resolve relations with Onderon, quell the independence movement on Kuat, or crush the Revenant Armada operating out of the Empress Teta system. These seeming minor failures would come back to haunt the Imperial Republic later in its history.
After the wounding of Emperor Christopher Fel during the ill-advised Nagai Expedition, Chancellor Selkisto placed his own daughter Calliope on the Imperial thorn, who reigned briefly as Empress Calli. As an Onderon Royal, and Senator from Talus, the brief reign of Empress Calli represents the zenith of the Imperial Republic, coming close to the Jedi ideal of a republic of wise representatives guided by a Jedi Council.
This ideal situation did not last long. Disturbed by Sith infiltration and an assassination attempt, First Empress Calliope proved unwilling to serve as Empress for a prolonged period of time. Amid the distraction caused by revelations of renewed Sith infiltration of the core worlds, PGA and Imperial forces allowed the Revenant Armada to slip free of the Empress Teta system and move on Nar Shaddaa, effectively cutting off the lower Corellian from the galactic core.
After ineffective posturing, PGA and Imperial forces were out maneuvered by the brilliant Revenant Admiral Takaki, who seized the capital, Coruscant. The Emperor and the PGA fled to fortified Antilles. A short time later, the Black Sun Pirate Armada under the command of Huttila the Hutt appeared in the Roche Asteroid Field, effectively cutting the Perlemian Trade Route. The Imperial Republic appeared doomed.
Under the energetic leadership of General Selkisto, Velmoran-PGA forces were able to invest and besiege Coruscant, but were unable to break the hold of the Revenant Armada. Local forces supported by small PGA flotillas managed to chase the pirate fleet from the Roche Asteroid Field, but were unable to bring about a decisive victory over the pirates, who remained at large under the command of the wounded Huttila the Hutt.
Seeking to break the deadlock, Revenant forces brokered a secret deal with Gromas 16, the infamous Blood Moon, who treacherously betrayed the PGA and the Velmoran oligarchy, allowing the Revenant Armada and the pirate fleets to increase their disruption of the Perlemian. Seeing their successes, Sith forces on Korriban and Ziost began to stir, looking for easy victories over the once powerful Empire.
As Imperial fortunes waned, more and more local systems were forced to look after their own affairs and self-protection. The PGA fell back on its core systems, Velmor,[=break in data-stream=] ;Mon Calamari and Talus, while scattered Imperial forces were forced to fend for themselves. This marks the end of the time of the Imperial Republic; the history of the PGA continues under the heading, "Rise of the Second Velmor-Onderon Dynasty."