You want the three regions? Try having Barca ask for them, Mendicant might be more inclined to listen. Demanding gold just to open peace talks is a sure fire way to kill any chance of peace stone dead.
It's been all an awful misunderstanding, it seems Barca forgot to ask for them before the declaration of war. Would Mendicant get deposed by their servants for not sending them to destroy the enemy realms, but they would be willing to give back these regions? Mendicant can pretend to be "more inclined to listen", but what does it mean?
Maybe last time he was inclined to listen while being absolutely sure he would keep them. What Barca got was time wasted in useless negotiations and an enemy army at the gates of the capital. I'm more inclined to think that the only peace talks will start by the renounce of Barca to the stolen regions. Please correct me if I'm wrong.
