De Jure boundaries are fundamental to determining who gets what land at the end of some wars in Crusader Kings II, and understanding the mechanics may save you some heartache ahead of time.
Holy Wars and de jure:
When declaring a holy war on an infidel state, you will be asked a holy war… for what?
Holy Wars for Leon, Toledo, Valencia, and Cordoba, that’s what for! But Leon, Toledo, Valencia, and Cordoba, are many things. Each is a county, a Duchy, and a de jure Duchy.
However, we can tell that the casus belli is not related to counties, because in this case the county of Cordoba isn’t a part of the Realm we are declaring war on. The Emirate of Valencia does however hold lands in Each of the de jure duchies listed in the various casus belli.
Looking at the tooltip of one of the casus belli choices will verify that de jure Duchies are the focal point of the casus belli, and should thus be the focal point of your war as well.
So, in a holy war for Leon, we would compare the realm map with the de jure map and see that there are two counties that are 1) owned by the Emirate of Valencia, and 2) de jure part of the Emirate of Leon, Those being Leon and Zamora. If Aragon defeats Valencia in this war, it will (almost certainly) gain both of these counties. If Valencia happens to be in another war, or gets in one, and the counties Leon and Zamora are captured by a third party, then you could win the war, and yet not end up with the counties you sought. It can happen, but it doesn’t happen very often.
Since you will be able to expand along de jure lines, you will want to take a long look at the de jure map, and decide which region you wish to contest in your holy wars. Your opponent may only hold one county in one de jure duchy, and all five in another. If you are confident you can win the war, you may as well go big. If you don’t, your opponent will.
De Jure and Crusades
With patch 1.05, the role of de jure in Crusades has changed slightly. Instead of looking at the lands held by a ruler in a de jure duchy, you will instead be battling the opponent over all the lands in a de jure Kingdom. Compare the Realm and de jure Kingdoms maps to see which lands are contested.
De Jure and War Score
Once you have chosen the de jure Duchy you wish to claim via a holy war casus belli, make sure to focus your efforts their when besieging your enemy. While any captured holdings will add to your warscore, the contested holding will count for more in War Score calculations. Taking and holding the contested territories will be a faster path to victory than uncontested enemy territory.
De Jure Topics: