The war began when he, along with his friend and apprentice Darth Malak, led an invasion of the Galactic Republic in the year 3959 BBY, returning from the Unknown Regions with a massive Sith fleet, seizing control of Korriban, revitalizing the Sith Academy there and gaining access to the Star Forge early on during a mission to Rakata Prime. The Jedi Civil War, also known as the Second Sith War, the Old Republic Insurrection, the Malak War, and by the Mandalorians as the War of the Star Forge, was a devastating conflict that began when the Jedi Knight Revan, who had led the forces of the Galactic Republic to victory in the Mandalorian Wars, founded his own Sith Empire and declared himself the Dark Lord of the Sith.
To them, they are both Jedi-with different philosophies.' ― Mical ' The reason the Jedi Civil War was named such, was because few in the galaxy can recognize the difference between the Sith and the Jedi. Dark Lord of the Sith Darth Revan (early/mid war).