If you really want to know your Sith history, pick up the new essential chronology. It's pretty much a history lesson of Star Wars. First off, KOTOR happens 3995 Before Battle of Yavin (BBY). The first republic existed about 25,000 BBY. An group of dark-siders first created an army of Frankenstein-like monsters and waged war during the "Hundred-Year Darkness." They were defeated and they fled beyond Republic borders to uncharted space where they discovered the Sith species. They grew powerful and became the "Sith Empire" (around 5000 BBY) Some stuff happens and basically they come back to the Republic that sparks "The Great Hyperspace War" They fight, the Sith lose. Then some dark spirits come back and teach Exar Kun the dark side and he becomes uber-powerful. He creates many converts and they start another Sith War. Then the Mandalorian Wars (3995 BBY) occur leading to KOTOR and the second Sith war. All ends well. 2000 BBY, Some Jedi just break away from the council and decide to found a new order of the Sith. Lord Hoth's Army of Light fought a Brotherhood of Darkness. After the good guys win, a Darth Bane establishes a strict dictate that there can only be one master and one apprentice at any time. This way they could consolidate power until they were strong enough to re-emerge. 1000 BBY, a Chancellor Tarsus Valorum (not Finis Valorum, the one in TPM) make some reforms. Giving the Senate (and individual systems) more power, dismantling the army, and letting the Jedi Order become a judicial branch of government. Insert Star Wars movies here. Basically the "First Galactic Empire" probably means the first time the entire galaxy is together, with no wars. (Rebels did not count). And Ki-Adi Mundi was probably just referring to the war between the Army of Light and Brotherhood of Darkness. Maybe his dates were a bit off.