The Dark Galactic War, occasionally called the Dark War, was a war between the Sith Empire and the Galactic Republic Union lasting for a total of 24 years. The conflict was ultimately the result of an over 1000-year grudge held by survivors of the old Galactic Empire against the Republic for their defeat in the Second Imperial Civil War.
With the Galactic Empire defeat in the Second Imperial Civil War., the Galactic Alliance decided how to deal with their fallen enemy: theey ordered the Military to exterminate all remnants of the Sith. But one Sith Lord and a group of survivors escaped the Alliance's slaughter of their kind and fled to the Unknown Regions. There, he re-founded the Empire, assumed the title of Lord Emperor, and created a council of other Sith Lords to rule under him. Using the power of the dark side, the Emperor kept himself alive for over a thousand years after the Second Imperial Civil War, rebuilding the Empire's strength and promising his people revenge on the Alliance and the Jedi.
Believing the Sith to be gone for good, the Galaxy would establish a new government, known as the Galactic Republic Union.
Over a Thousand years of military build-up would happen before a shift to direct preparations for invasion. After such a lengthy build-up, the Sith fleet had grown to enormous numbers; and now Imperial agents had begun to operate in secret, arranging alliances both within and outside of Republic space.
Imperial operatives were successful in securing an alliance with the Chiss Ascendancy, also support from the Monarch of Bohan and as well as the financial backing from the Intergalactic Banking Clan. The Emperor secretly mad alliances with governments in key positions in the Republic's Outer Rim systems. Before a shot had been fired, the Empire had already secretly brought the Belkadan, Ruuria, and Sernpidal systems of the Dalonbian sector under its control. These would prove to be vital assets for the Empire in the early days of the war.
As invasion drew nearer, the Imperial Navy's war games would reach fever pitch—military exercises became a daily event. On the eve of war, the Imperial fleet gathered in key staging locations just outside of Republic space, the Lord Emperor ordered the invasion of the Republic.
For centuries, the ancient Sith homeworld Korriban had been guarded by a vigil of Jedi and a fairly small contingent of Republic troopers. At the onset of the war this garrison was overseen by Jedi Grand Master Jel Wilkins and two Jedi Knights.
In a move which caught the Republic defenders completely by surprise, a Sith fleet of over 30 warships launched a massive assault on their long-occupied holy world Korriban. The Republic and Jedi defenders quickly fell to the Imperial attack, while Sith Lord Shadow Council member Darth Prion battled the Grand Master Wilkins and the Jedi Knights on the orbital station.
With the Jedi Knights slain by the superior Darth Prion, Wilkins escaped the fighting, but not before leaving Darth Prion to die in a lightsaber duel. With a minimal effort due to overwhelming force, Korriban was captured by Imperial forces and brought under Imperial dominion once more. The attack was so successful that an extended period of time passed before the Jedi Council even learned of Korriban's loss. Darth Prion was brought back from the brink of death by the Emperor and the first time in centuries The Emperor took a new apprentice.
Fall of Klusage shipyard
With the capture of the Korriban, the Sith Empire turned its sights on a valuable new target: the Klusage sector. Klusage was the home of significant Republic starship manufacturing facilities which presented a tempting target for the invading Imperial forces. The Imperial naval forces quickly moved on Klusage, which was entirely undefended with the Republic forces still scattered. Various Sith starfighter squadrons attacked the shipyards and destroyed the orbital ring that made up the station.
The Sith forces continued to press, and conquered the world itself. Much as would continue to be the case as the war pressed on, the Imperial forces executed any civilian or government workers who refused to swear loyalty to the Empire. The Republic military personnel were not granted such mercy, they were simply hunted down and summarily executed as enemies of the Empire.