Battle of Galidraan
The Battle of Galidraan was an event taking place in the year 956 ARR. For several years prior, a vigilante group called the True Mandalorians was active in the Outer Rim. The True Mandalorians traveled up and down the Outer Rim, defending planets from pirates and criminals. Motivated by honor, they would defend planets without even charging those they kept safe.
This, however, brought them to the attention of the Jedi Order. The Jedi had been actively destabilizing the Outer Rim, and saw the True Mandalorians as an obstacle to their schemes. A Jedi task force, command by Jedi Master Dooku, was deployed to eliminate this obstacle. Dooku's task force formed allied with the mercenary group Death Watch (who would later join Dooku's Separatist Alliance) and set a trap for the True Mandalorians.
Death Watch attacked the planet of Galidraan, hoping to lure the True Mandalorians to them. Sure enough, the True Mandalorians arrived on Galidraan to protect the local people. Dooku's Jedi wasted no time in springing the trap. Caught between the Jedi and Death Watch, the True Mandalorians were massacred and wiped out completely. Thus, the Jedi Order eliminated a threat to their destabilizing plans for the Outer Rim.