Following on from my question on the previous page...
When I retook the county that my duke liege taken from me (without me having the opportunity to resist), he instantly took the county of the other vassal count in the duchy as his own.
So what is going on here? If a duke has no counties in his duchy, he is able to immediately seize the county of a vassal of his without their consent and without opportunity to resist?
This would have the potential to instantly end one's game? If I had not had a second county, it would have been game over for me when the duke seized my primary county, and there would have been nothing I could do about it.
I'm playing with half-demesne rules, which may make such episodes more likely to happen.
To my knowledge: Yes. If the holder of a Duchal or Kingdom title loses all their holdings (i.e. county- or barony-level titles) they will usurp one within the de jure area of their title.