Ditz: Yes, vassalage basically is an alliance on steroids. You get a certain amount of money from your vassals and their lands count as your own. Everything else is just like a normal alliance. Vassals will still act on their own; heck, I had it happen that two vassals of mine (Denmark and Poland, while I was playing France) went to war with each other, which, of course forced me to choose which one to keep as my vassal.
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