Further questions:
If some form of vassal was attempting the military takeover of his lieges land, what sort of things we he do? just take as much land as possible, steal weapons, just find the biggest army of the enemy and attack?
What would enable a smaller force to overcome the larger force of their former lords?
Were these conflicts generally settled through intrigue or warfare?
Say a general had a good sized army at his disposal, what would he do? Raid villages? attack castles? steal from armories? steal supplies or attack supply lines?
I fear video games and movies may have spoiled some of my views, and I'm sure you could see that in my questions. I realize my questions are a bit general (1000 years is a long time) so if you could share facts about specific incidents and rebellions from throughout this time period that would be great. If the questions are TOO general I can remove this and rephrase.
A reply to /u/Asevio
Hate to reply in this fashion to an enthusiastic post, but you are correct that this is too general. And as such, either you can expect a comprehensive survey, or a series of anecdotes that can be both illuminating and misleading.
All that said, let me recommend several topics to read up on.
The Swiss. Not only about their military prowess in late medieval / early modern era. But on how they formed in the first place, in the 14th century, and how their relationship with the Habsburgs and the French evolved up to the 1600s.
The Albigensian crusade. They formed a schismatic branch of latin Christianity in the 13th century, which led to a rebellion, which then led to a crusade against them. This plays into the French political system at the time.
Get started with those, and at the risk of getting yelled at by other AH flairs, start with the Wikipedia pages. I don't know your level of interest nor commitment, so I won't waste anybody's time with a list of formal references.
Cheers.