The Mandalorians had never forgotten their humiliating defeat at the Republic's hands during the Great Sith War. With his Neo-Crusader warriors prepared by a decade of conquest, Mandalore the Ultimate decided the time was right and launched an assault on the Republic. Several Zabrak colonies fell to the Mandalorian advance, under heavy blaster fire and the shadow of Basilisk war droids.
Finally provoked into action, the Republic appealed to the Jedi for military support, but the Council refused. The Masters believed there were greater forces at work behind the Mandalorian invasion than a simple lust for war. They wanted to remain apart from the conflict, believing the true threat would reveal itself in time.
However, some younger Jedi disagreed with the Council's edict. These Jedi would form a splinter group, the “Revanchists,” and answer the Republic's call for help.