Sith army

The Sith Lord Darth Bane served in a Sith army during the dark age of Old Republic, a thousand years before the Clone Wars. While serving in the Sith army, Bane realized that infighting and greed from other dark side warriors created a weakness. The infighting eventually led to the defeat of their dark side order, as the Jedi Order was able to all but destroy the weakened Sith.