Quote Originally Posted by Xdeathfire
I actually have done this with all of the Catholic nations and has essentially made every Catholic nation allied with every other Catholic nation creating a peace within Europe that I have never seen before. All the computers do is to build up cities and train tons of stacks that patrol their borders which lead me to believe that with some careful diplomacy, I may be able to incite a huge war in Europe.
Unless you are using a mod I believe they will eventually attack you. There are some triggers in the game that mean even your closest, bestest ally will eventually attack you if he has noone else to fight...

Still, interesting...