Massacre at Ossus

The Galactic Alliance was absorbed into the Empire after the Sith-Imperial War, and the Emperor called for the Jedi to surrender as well, and subject themselves to the will of the Empire. The Jedi refused the Emperors demand and withdrew to the Jedi Academy at Ossus.

The Sith had no desire to let the Jedi survive, and Ossus was subsequently attacked. This attack is referred to as the “Massacre at Ossus,” where most of the Jedi Knights there were killed. Kol Skywalker sacrificed himself in the defense of Ossus, giving his son Cade time to escape during the confusion.