Understanding the theory and practice behind earning a CB will ensure that you never have to be at peace for long. What I’m going to be focusing on instead is how you actually go about earning these CBs. If that’s the information you’re looking for, take a look at the Casus Belli section of the CK2 Wiki. Far too many for me to go through them and explain what they all do. Although it might not seem like it when you start as a Catholic ruler, there are a lot of Casus Bellis (CBs) in Crusader Kings 2.