Darth Bane created the long-standing 'Rule of Two' when he took his apprentice, Darth Zannah; one master, one apprentice. This strategy maintained the order for many years until the deaths of Darth Sidious and Vader aboard the Second Death Star.

Around 130 A.B.Y. Darth Krayt put into effect the 'Rule of One': one master. It is acknowledged that Darth Krayt founded this rule. However, is it not possible that the 'Rule of One' existed in all but name under Darth Sidious?

Take into consideration that:

1. Darth Sidious has had, at least, three apprenices (not counting Luke

Skywalker) and ran through them like water on a desert.


2. Darth Sidious created clones of himself to facilitate his return in the

event of an apprentice's betrayal (*coughs overtly* Darth Vader).


3. Darth Sidious never actually trained Darth Vader as an apprentice but an

enforcer.

All this considering, I think that Darth Sidious kept Vader for the tradition of the 'Rule of Two' rather than for the purpose of succession. In fact, the wole of my arguement is summarized in a Palpatine quote from the Telos Holocron:

"Choose someone as a successor and you will inevitably be succeeded.

Choose someone hungrier and you will be devoured.

Choose someone quicker and you won't dodge the blade at your back.

Choose someone with more patience and you won't block the blade at your throat.

Choose someone more devious and you'll hold the blade that kills you.

Choose someone more clever and you'll never know your end.

Despite these cautions, an apprentice is essential. A Master without an apprentice is a Master of nothing."

--Darth Sidious


I would also like to invite anyone who likes Darth Sidious/Palpatine visit my You Tube channel for quite a few Darth Sidious music videos; I hope you enjoy them:

Electricboa's You Tube Channel