501st Legion

The 501st Legion, also known as the 501st Clone Battalion, and Vader's Fist, was a famous legion led by Anakin Skywalker, Clone Captain Rex, and later Commander Appo.

History
The 501st was along the battalions that the Republic deployed to reconquer Umbara from the Separatist Alliance. During the campaign, Anakin Skywalker was recalled to Coruscant by the Jedi High Council at the request of Supreme Chancellor Sheev Palpatine, leaving the 501st under the command of Jedi General Pong Krell. Although he was a recognized war hero with a distinguished record of service, Krell became a Separatist spy after turning to the dark side of the Force. He deliberately sabotaged his own strategies to undermine the clones, whom he regarded with contempt and disgust.undefined

Krell's betrayal was revealed after he tricked the 501st and the 212th into fighting each other, causing clones on both sides to kill each other by mistake. When the battalions mutinied against him, the fallen Jedi slaughtered many clones but was ultimately captured while attempting to escape. In response to his actions, Krell was summarily executed by his most loyal soldier, "Dogma," who was subsequently taken into Republic custody for killing an officer.