Help! I've got a duchy in my realm I don't want.

[POemil]

Hi everyone,

So I need some help. I am playing as the ERE, and one of my overly eager vassals usurped the duchy of Brunswick. While I appreciate my vassal's effort, I like to have 'clean' borders. Hence I would like to lose these holdings.
Unfortunately this appears to be more difficult than I anticipated. My first thought was to revoke the title and give it to a king not part of the ere. However to give the title away the heir has to be in my realm, and I can't seem to invite any heir.
My second plan was to imprison him and have him revolt. This worked at first, the vassal revolted, however even when I surrender the duchy remains part of my realm.
I then reloaded and crushed his armies hoping nearby neighbours would invade and take the land. This worked partially; denmark took one county. This was however in a timespan of 15 years and there were no signs of any other neighbours attacking them.

So tell me how do I get rid of them? And why is it so difficult to lose land?

 

[Hetzerr]

Reload your game as a muslim ruler, declare holy war for the duchy then save the game and reload as your original country and surrender.

 

[Cymsdale]

Revoke the titles and assign them to a courter with no holdings. Then bring up the diplomacy window with the leader of the realm you want to transfer the territory to and choose transfer vassalage.

 

[Octavio]

You could convert to catholicism and grant the titles to the pope...

No, seriously, no idea. Did you check if the war with your vassal was one about independence? Never thought it would be so difficult to lose territory...

 

[Yenzen]

You could try inviting the heir of a neighboring realm of the same or a higher level than you and grant him the land.*

Otherwise you could use cheats to use the "give_title" cheat to turn it over the the neighbor king.

* Won't work if you have High CA

 

[Isaios]

Your only viable option would be inheriting it out of the realm, but that's dependent on CA.