Quote Originally Posted by LordK9 View Post
I don't believe (but have no way of confirming or disproving) that they are treated as one entity. Why? If you look closely, rebels are marked differently on the map. Sometimes several provinces are marked the same but others will be marked differently.
There is a simple proof. When you attack the rebels first, you are asked if you are sure you want to attack this province belonging to rebels. Before attacking every next rebel province this question does not pop up, so you may assume you are at war with all/any rebels. The only exception is when you get an auto cease-fire with rebels (for the conditions of it see elsewhere). Then any new invasion of the rebel province is preceded by the above-mentioned message.