In 1 BBY, during the Galactic Civil War, Imperial forces under the command of High Inquisitor Jerec subjugated the moon of Sulon.
Prior to 1 BBY, Sulon colonists who were opposed to the Galactic Empire and the SoroSuub Corporation's handling of the moon, quietly organized themselves in armed resistance. They constructed a geothermal energy distribution system called G-Tap to secure their independence from outside power sources and organized colonization efforts to the planet Ruusan.
Eager to clamp down on resistance activity, the Empire sent a small force supervised by the High Inquisitor Jerec to subjugate Sulon and eradicate the Rebel presence there. Only an Imperial I-class Star Destroyer was sent, as it was believed the operation would not require any larger vessel. The Inquisitor Jerec's flagship, Vengeance, was commanded by Captain Thrawn - assigned by Emperor Palpatine himself - while the ground forces were led by Major Noda.
The military operation was conducted with a dual purpose in mind, both destroying the Rebels on Sulon and at the same time lay the blame on the Rebel Alliance by making it out to be their doing. To this end, all soldiers and vehicles were marked with Rebel insignias, although the hoax was only partially successful.
Special elite soldiers from the Empire's Ghost Battalion attempted to track down the local Rebel leader, Morgan Katarn. They destroyed eleven homesteads including Katarn's and Danga's and massacred entire families in the process, all in an effort to discredit the Rebels further. Although the raid was successful, they failed to locate Katarn.
After surviving the initial assault, Katarn reunited with other Rebels who decided to get organized and resist further, thinking that the primary target was their G-Tap installation in order to force them purchase a and pay taxes. Katarn believed that they should keep hiding, because the attack was only a ruse to expose and destroy them; Skorg Jameson's voice overruled Katarn's saying that the Sulonese should protect their autonomy and prove their power in the Rebellion.
The Rebels voted for war and organized at the installation as highly modified Imperial probe droids espied on the participants, and reported their movements to Jerec.
AT-ATs and AT-STs made their way towards the G-Tap, supported by modified assault craft. The colonists lost two squads in the first thirty seconds. Katarn also lost most of his team.
After hours of fighting, the remaining Rebels barricaded themselves in the cavern, and attempted to hold out for as long as possible. Despite their efforts, the two contingents of stormtroopers pushed them in the main chamber and overwhelmed them after a brief fight. Most of the Rebels were killed, save the leaders who were brought on-board Vengeance to be interrogated. Katarn, who was Jerec's primary target, was finally brought before him; refusing to cooperate, the old man was executed by the Dark Jedi himself.
Kyle with a recording showing his father's fate.
Having removed all resistance from the moon, the Galactic Empire took direct control and the Inquisitor Jerec became Governor, having a Government House built in the center of the capital, Barons Hed.
Outside the city walls, the heads of Rebels were put on display, with Morgan Katarn's head being prominently displayed, impaled upon a spear made up of bones by one of Jerec's Dark Jedi minions, Maw.
Kyle Katarn received word of his father's death at the hands of Rebels, and became more dedicated to his role in the Empire. He would eventually learn the truth of the slaughter and defect to the Rebels, and eventually became a hero of the Alliance, the New Republic, and the New Jedi Order, in addition to avenging Morgan's death.