George Lucas' has previously explained how exactly the Sith Rule of Two has worked across generations in the Star Wars galaxy. Despite the two Force-wielding groups always being at odds with one another, the Jedi and the Sith have very different methods of training their respective warriors. As evidenced by eras like the High Republic and the prequel trilogy, the Jedi train thousands of people from across the galaxy in the ways of the Force.
The Sith, however, have a very different method. The Sith prefer to scheme, plan, and plot from the shadows, always consisting of only two Force-wielders - one apprentice and their master. This has been known as the Sith Rule of Two for a millennium, though Star Wars' core films in the Skywalker saga have offered little in the way of details about the concept. That being said, George Lucas sat down with Paul Duncan in the latter's book, The Star Wars Archives: Episode I-III 1999-2005, and explained how the Sith Rule of Two - which Palpatine potentially broke - works in the eyes of Star Wars' creator.
Lucas Understood The Rule Of Two As The Only Stable Sith Order
Lucas mentions the Rule of Two as the only way the Sith can maintain a stable order. According to Lucas, the Sith Lords were in control of the galaxy for a very long time. However, due to their greed and power-hungry ways, these dark side s began killing each other in a bid for power. As a way of seeing who can become the ultimate Sith Lord, they kill rather than vote, in an almost medieval feudal system.
In the book, Lucas also mentions that at one point there may have been thousands or even millions of the Sith at large in the galaxy, not unlike the Jedi before the rise of Darth Sidious. Although, after the killing started, centuries ed and resulted in only two Sith Lords being left alive. In Lucas' mind, this is when the Sith Rule of Two was born, which allowed the longevity of the evil Force-wielders, as opposed to the previously unstable method of rising the ranks through murder.
Every Sith Apprentice Naturally Strives To Become A Master
As Lucas goes on to explain, every Sith apprentice craves the power of their master. These last two Sith envisioned by Lucas were said to have been master and apprentice, though the former would keep a close eye on the latter. While Lucas views the Rule of Two as stable in that it has lasted for generations, it also did not last, as every apprentice looks to acquire their own learner to usurp their master. Similarly, every master is attempting to recruit another apprentice as a means of replacing their current one in order to preserve their own power.
How Darth Vader & Palpatine's Plans For Luke Fit With The Rule Of Two
Lucas' explanation of the Rule of Two is heavily evident in the original Star Wars trilogy through Darth Vader, Emperor Palpatine, and Luke Skywalker. As was shown in the prequel trilogy, Emperor Palpatine was the Sith master from before the Skywalker saga. Throughout the prequels, he had apprentices in Darth Maul, Count Dooku/Darth Tyrannus, and eventually Anakin Skywalker/Darth Vader.
Palpatine and Vader were, therefore, the Sith master and apprentice of the original Star Wars trilogy. In Return of the Jedi, both Sith Lords showcased how their plans fit into the Sith Rule of Two. Beginning with Vader, Return of the Jedi centered on the dark Lord attempting to recruit Luke as his apprentice. While Luke was attempting to bring Vader back to the light side of the Force, Vader was equally attempting to convert Luke to a Sith. This would have undoubtedly ended in the death of Palpatine should Vader's attempts have succeeded, with Vader taking his place as decreed by the Rule of Two.
Similarly, Return of the Jedi's final act centers on Palpatine swaying Luke to the dark side, resulting in a duel between Vader and Luke. After Luke defeats Vader, the Emperor implores Skywalker to kill his father and take his place as Palpatine's Sith apprentice. Luke refuses, which ends in Vader's redemption and the defeat of Palpatine in the name of the light side of the Force. If either Vader or Palpatine had succeeded, the Sith Rule of Two would have been followed, rather than broken, until the time of the sequel trilogy as shown in the Skywalker saga.
Not All Sith Are Fallen Jedi (According To Lucas)
One of the other interesting elements Lucas divulges about the Sith in Duncan's book is that not all Sith are fallen Jedi. Lucas mentions Count Dooku, who eventually fell to the dark side and became Darth Tyrannus, as shown in Tales of the Jedi. Lucas explains that these Jedi that fall to the dark side are then scooped up by Palpatine. Because the apprentices are already strong in the Force due to being former Jedi, they require less training than others.
However, there are some instances across the Skywalker saga of Sith that were not originally Jedi. The likes of Darth Maul and Savage Opress were not Jedi before becoming Sith, unlike Darth Tyrannus, who succeeded Maul as Palpatine's apprentice. Despite characters like Anakin, Dooku, Asajj Ventress, and Ben Solo all being Jedi before falling to the dark side, Lucas has made it clear that Sith can come from anywhere, rather than simply being fallen Jedi warriors.
Do All Sith Have To Be Force-Sensitive?
An interesting question to ponder is whether all Sith need to be Force-sensitive. As per some quotes from Lucas in Duncan's book, this may not be the case. Lucas mentions that Anakin fell to the dark side during Star Wars: Episode III - Revenge of the Sith after killing Mace Windu. Interestingly, Lucas then remarks that Anakin asked Pé to him and together they could become more powerful than the Emperor.
This seems to hint that, if Pé had chosen to Anakin in his quest for power, she would have served as his apprentice, despite not being Force-sensitive. Anakin/Vader would have been the master after replacing Palpatine, with Pé his underling and replacing what Vader had become. While no instances of non-Force-sensitive Sith have been mentioned in Star Wars besides this, the concept is interesting to ponder.
