The Galactic Sith Purge was an intergalactic genocide of the Sith from 3,936 to 3,931. The Treaty of Coruscant formed the Grand Alliance which included the Galactic Republic, the Jedi Order, and the Mandalorian Empire. The Galactic Coalition saw a Sith threat and knew the galaxy would be better off without it. They planned for an attack on the Sith stronghold of Korriban. Mandalore and the Republic thought it would be over then; the Jedi knew better.