Each Christian or Muslim denomination can have one Defender of the Faith. It costs 500 ducats for a country to claim the title. Countries with female rulers, regencies or which are subject nations cannot claim the title. Being Defender of the Faith gives the following modifiers (without ):
|+5%||Morale of armies|
|+5%||Morale of navies|
|−0.03||Monthly war exhaustion|
|+1||Yearly papal influence|
Additionally, all other countries of the same religion get a +10 “Defender of Faith” relations boost with the title holder.
Countries automatically call the Defender of the Faith of their religion to arms if attacked by a nation of another religion. Since patch 1.8, it seems the Defender of the Faith gets a call to arms only for countries on the same continent or sharing their border. The Defender of the Faith doesn't get a call to arms if the country attacked is a co-belligerent (e.g., if France is the Catholic Defender of the Faith and Venice (Catholic) is allied with Serbia (Orthodox), then if Ottomans (Sunni) attack Serbia and make Venice co-belligerent, France doesn't get a call to arms).
Catholic countries that hold the Defender of the Faith title cannot be excommunicated by the Papacy, regardless of relations.
The Defender of the Faith loses the title, but no prestige, if they refuse or lose the war.
If Defender of the Faith refuses a call to war, it gets a 5-years truce with the country that was calling. Therefore, if your ally is Defender of the Faith and you have a common enemy of the "defended" religion, this ally will not be able to join you in an offensive war against this enemy, as AI wouldn't break a truce.
Note: If the title holder ends any war with a result other than a white peace or victory, the title will be lost.
|Available only with the Emperor DLC enabled.|
Depending on the strength of the Faith (based on number of countries), multiple tiers of Defender of the Faith are available:
|Amount of countries||Effect|