Yes but the problem is that it works only one way, against you.
In my experience the enemy lords seem to always come back with huge armies made of trained troops.
Take the Khuzait for example, in every playthrough that I tried to overthrow them and take over their cities, they just kept coming back with endless armies, and each time a huge chunk of their army was horse archers.
How can they come back everytime with horse archers like nothing happened is beyond me.
Cutting their heads off like somebody suggested is not really an option because:
1) If you want them later on as your vassals you gotta keep them alive
2) Even if you don't need them and don't mind executing them, doing so, for some odd reason will upset your vassals and in no time you will have -100 relation with every single one of your vassals.