Is the Ai always guaranteed to break aliances?

[oz_wwjd]

I was playing as the Byzantines. I've had an alliance with the Papacy and the Hungarians among others for about 20 years now,until the hungarians decided to invade Wallachia with 2,500 men against my 600 man garrison and the pope decided hitting Naples with Urban Militia,spearmen and Feudal Spearmen was a good idea,when I had a Jedi 8-star general leading a mix of Varangian Guard and byzantine infantry was a good idea.Needless to say,both invasions were crushed quickly with many losses to them,but can I depend on them to do this,whenever they feel like it? I'd hoped XL 3.0 would be a bit better in this respect.