The four-part Umbara story arc in Star Wars: The Clone Wars was one of the show’s darkest plotlines, and it had the potential to create a new origin for Order 66. The Clone Troopers are introduced in the Star Wars prequels as being little more than organic automatons, but Clone Wars-era non-movie material from both the canon and Legends timeline establishes that all clones, from the standard grunts to elite ARC Troopers, have free will and a genuine belief in fighting for the people of the Republic. Their true purpose, however, was Order 66, which could have had a significantly different origin in the canon timeline, thanks to The Clone Wars’ Umbara arc.
While Clone Troopers enjoyed comradery with their Jedi generals in canon and Legends, their ultimate purpose was to kill them when Order 66 was issued, initiating the Jedi Purge as part of Palpatine’s master plan. In Legends, Clone Troopers were indoctrinated to follow the order, no matter how they felt about their Jedi allies, but canon takes it a step further, revealing that all clones have a brain implant that compels them to follow Order 66, changing their normally-friendly personalities in the process as well. As shown in Star Wars: The Bad Batch, however, the Order 66 effects of the control chips can eventually wear off.
Related: Order 66 Did More Than Just Make Clones Kill The Jedi
The Clone Wars’ four-part Umbara story arc gradually revealed that Anakin Skywalker’s temporary replacement, Jedi General Pong Krell, loathed clones and purposefully sent scores of troopers to their deaths against Umbaran Separatist forces. After orchestrating a deadly friendly-fire incident, Captain Rex and elements of both the 501st and 212th arrested and executed Krell for treason.
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