So what do you do with a 100% warscore?

[grumbold]

Playing as Scotland, Duke Maél-Snechtai revolts when I try to imprison him for being the head of a plot to usurp the throne. 1 year later I've occupied all his holdings and defeated his armies. He owns nothing. Warscore is 100%. Yet I cannot enforce demands and end the war. What on earth is going on?

 

[nyah]

Is he at war with somebody else? If he is and they are occupying one of his holdings you won't be able to force peace until the other war ends, or the holdings are no longer held by his enemy.

 

[grumbold]

I own everything.

 

[grumbold]

He's now offered to surrender completely to me, but there was no way it was letting me enforce it myself. Looks like the typical Paradox snafu, each patch fixes 50 things, breaks 10 and introduces something new to make the game harder for the casual player... I suppose I should be used to it after 13 years.

 

[Prime624]

You have to go into diplomacy and ask him to surrender. He will say yes and the war will end immediately. You won't even need to wait for him to respond.

 

[Mutineer]

he could been in war with somebody else and lord of some abscure barony outside his main counties. you migth miss that.

 

[Ravenous.BE]

If you hoover your mouse over the greyed out "send" button in the diplomacy screen, it will tell you why you can't send it.
In case that doesn't work, I suggest making a bug thread about it with a save game file.