What is a Holy War
Holy Wars are special wars that are started with one of the Holy War Casus Bellis. This type of War differs from other Wars as Rulers of the same Faith. It allows a Casus Belli to be just based on the defending ruler’s faith in comparison to your own. For instance if you are a Catholic you will be able to use a Holy War Casus Belli towards someone of the Asatru or Muwalladism.
These Holy Wars have a lot of unique differences compared to other Casus Belli Claims. The first major difference as they don’t cost Prestige, but cost Piety instead. The second is that there are only three (3) Holy War Casus Bellis to choose from; Kingdom, Duchy and County. The third main difference is that anyone of the defenders faith can join in as a defender and does not have to have an alliance to do so. The fourth main difference is that if you are the defender you will have a decision option to convert to enemy attacker’s faith, and in cases this can save you losing some or all of your realm if you are in a bad position.
To Declare War and use a Holy War Casus Belli you will need to be a neighboring ruler and meet the requirements for the Casus Belli. The base requirements are below and of course can be modified depending on innovations, culture, and faith tenets.
Casus Belli Requirements
| Casus Belli | Piety Cost | Level of Devotion |
| Holy War for Kingdom | 750 | Paragon of Virtue (4) |
| Holy War for Duchy | 200 | Faithful (2) |
| Holy War for County | 100 | Dutiful (1) |
You can declare a Holy War if you do not have the Piety cost at a Devotion Penalty that will put you down a Level of Devotion. I would not recommend going this option, but certainly is available. Another piece to note is that you can only do one (1) Holy War for Kingdom during your life time, so make sure to choose carefully.
The winner of the Holy War typically seizes All Counties in the targeted area for themselves. However, if the attacker’s Faith is has the Pluralist Doctrine or the defender has Vassals of the attacker’s own Faith in the targeted area, some or all Vassal Rulers in the targeted area may simply be transferred to the attacker instead.
Lastly, Holy Wars may be allowed or restricted between different Religious Families. A Religious Family is a group of Religions in the same branch. An example would be the Abrahamic Family (Christianity, Dualism, Islam, Judaism, Milete Tawuse Melek) condones Holy Wars against everyone. Religions are susceptible to Heresy or leaving a Faith for another when Fervor is low.