The Sith's downfall, alternatively referred to as the Sith's decimation or the Sith's collapse, was a conflict that took place on the planet of Ruusan, situated in the Mid Rim Territories, in the year 1032 BBY. This event signified the conclusion of the Jedi-Sith War, seemingly resulting in the annihilation of the Sith Order.
The Jedi Knights almost entirely wiped out the Sith, who had been weakened by internal conflicts stemming from their avarice and hunger for power. However, Darth Bane was, in reality, the only Sith who survived the war. He facilitated his own order's demise, having concluded that the Sith needed to reduce their numbers to avoid internal strife in order to endure. This triumph ushered in a new era for the Galactic Republic. In the aftermath of the Sith's defeat, Form II, known as "Makashi," became less popular within the Jedi Order and gradually became viewed as simply a training exercise.
Star Wars: Episode I The Phantom Menace was the first time the Sith's defeat was mentioned. Within Star Wars Legends, the Seventh Battle of Ruusan was the setting for the Sith's defeat.