The Sith Order’s Rule of Two was known to the Jedi by the start of the Star Wars prequel trilogy, yet some viewers may wonder how they knew of the doctrine, given its creation after the supposed destruction of the Sith. The Rule of Two states that there can no more or less than two Dark Lords of the Sith, with the greater Lord, the Master, ruling the galaxy alongside the lesser Lord, their Apprentice. The Star Wars canon and Legends continuities each offer a different explanation for how the Jedi discovered the Rule of Two.
The Sith Order once rivaled the Jedi Order in size, and the two ancient enemies clashed in numerous, galaxy-spanning wars. The Jedi ultimately prevailed because the Sith Order was plagued by dark side-fueled betrayals, leading the Sith to fight amongst themselves as much as they did against the Jedi. The Rule of Two was created by Darth Bane in the aftermath of the Sith Order’s defeat (known in Legends as the Ruusan Campaign), placing a check on the Sith Lords’ knack for backstabbing and allowing them to continue their existence in secret, orchestrating galactic history and the fall of the Jedi from the shadows.
Related: Star Wars Canon Has The Jedi-Sith War All Wrong According To George Lucas
Following the Invasion of Naboo (and the subsequent death of Qui-Gon Jinn) in Star Wars: Episode I – The Phantom Menace, Yoda and Mace Windu ponder whether the Sith Lord who killed Jinn was the Master or Apprentice, referencing the Rule of Two. The Sith hadn’t revealed their existence until the events of the film, so the Yoda and Windu’s knowledge of the Rule of Two would appear to be a plot hole. Non-movie material from canon and Legends, however, explain their knowledge as being tied to the defeat of Darth
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