- For information on individual religions, see religions and denominations.
The religion that a nation follows and how tolerant it is of other faiths is an important aspect of gameplay in EUIV. The religion of a nation will confer specific benefits, enable different mechanics, and affect diplomatic actions as nations of mutually accepted religions have a better chance of reaching agreements with one another. Religion is also connected to unrest and provinces of non-tolerated religions are more rebellious. The player has some control over religion by having the option to change the state religion, send missionaries to convert heathen or heretic provinces to the state religion, and carry out religious decisions.
- 1 Religion map
- 2 Religious unity
- 3 Tolerance
- 4 Defender of the Faith
- 5 Conversion
- 5.1 Province conversion
- 5.2 National conversion
- 6 Strategy
- 7 Achievements
- 8 Footnotes
Religious unity is the percentage of a country's development provided by provinces that follow the state religion or a positively tolerated heretic or heathen religion, excluding any assigned to trade companies.
- Provinces of the state religion always contribute 100% unity regardless of tolerance.
- Provinces of a heretic or heathen religion contribute a percentage determined by how tolerated they are.
The effects of tolerance on religious unity per province are as follows:
For example, suppose a Catholic country has a 10 development Catholic province, a 4 development Protestant province, and a 16 development Sunni province. If heretic tolerance is +1 and heathen tolerance is -2, the country's religious unity will be (100% * 10 + 50% * 4 + 0% * 16) / (10 + 4 + 16) = 40%
Ideas and policies which increase religious unity:
Religious unity directly affects the following:
- for each percentage point of religious unity:
- for each percentage point of religious unity below 100%:
|+1.0%||Stability cost modifier|
Countries have three tolerance values. These tolerance values are national, but have provincial effects depending on the province's religion, relative to the state religion.
Each point of positive tolerance gives:
Each point of negative tolerance gives:
|−10%||Local tax modifier|
|−10%||Local goods produced modifier|
Additionally, positive tolerance of heretics and heathens allows those provinces to contribute to religious unity (see above).
Note that there are some national ideas which remove all penalties for having negative tolerance.
Tolerance of the true faith
This refers to the state religion. For example, if the state religion is Catholic, Catholic provinces will use this tolerance value. The base value of tolerance of the true faith is +3, and there is no maximum value.
- +0.5 for ‘Trading in’ incense
- –2 for ruler with ‘Sinner’ personality
Tolerance of heretics
This refers to different religions within the same religious group. For example, if the state religion is Catholic, the religion group is Christian, and provinces that are Protestant, Reformed, Coptic, Orthodox, or Anglican will use this tolerance value. The base value of tolerance of heretics is −2. The possible maximum value is +3.
Heretic conversion events
Tolerance of heretics of ≥ 2 will allow provinces to randomly convert to those heretic religions. The mean time to happen is 5000 months, lowered by Innovative Ideas and having a neighboring province with the new religion while increased by having the Theocracy government type. Provinces with the "Religious Zeal" modifier will not receive these events at all.
A province is more likely to convert via event to a particular religion if a neighboring province has that religion. Adjacency is not required for most conversions. However, the following conversions only occur if a neighboring province has the new religion:
- Orthodox ↔ other Christian
- Buddhist, Shinto → Confucian
In addition, only Japanese-culture provinces can convert to Shinto as the result of a event.
Tolerance of heathens
This refers to religions of other religious groups. For example, if the state religion group is Christian, provinces that are of Muslim, Eastern, or Pagan religious groups will use this tolerance value. The base value of tolerance of heathens is −3. The possible maximum value is +3.
Ideas and policies that affect Tolerance of heathens:
Defender of the Faith
This section may contain outdated information that is inaccurate for the current version of the game. The last version it was verified as up to date for was 1.24.
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 or regencies cannot claim the title. Being Defender of the Faith gives the following modifiers:
|+5%||Morale of armies|
|+5%||Morale of navies|
|−0.025||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.
The most common way to convert provinces is the use of missionaries, but there are also several other methods. If you have the Cradle of Civilization DLC , you have the ability to directly convert your subjects' provinces to your subjects' State religion.
Missionaries are envoys that can convert a province to a nation's official religion. Missionaries slowly convert provinces over time: each month, the effective missionary strength in that province is added as ongoing progress, and when it reaches 100% the province is converted. If strength is insufficient (less than 0%), the province will never convert (although the missionary will not lose progress). An active missionary in a province will increase the unrest there by +6%. 
Ideas and policies:
Decisions and events:
|+2||Counter-Reformation||Decision: “Embrace the Counter-Reformation”||until one of the four “The Counter-Reformation Ends” events.|
|+1||Melchior Klesl||Austrian event: “Melchior Klesl”
||until ruler changes.|
The player can adjust the missionary maintenance cost by a slider on the economy interface between zero and full funding. Reducing the funding reduces missionary strength linearly, up to −5% missionary strength without funding. At full funding the costs of an active missionary per month is calculated based on the development and local autonomy of the province as follows:
The following ideas reduce missionary maintenance cost:
Base missionary strength is 2%. Modifiers that increase strength include:
- Advisors: +2% from an Inquisitor advisor
- Stability: +0.5% for each point of positive stability
- Piety: Up to +3% for Muslim states that are inclined towards Mysticism
- Patriarch Authority: Up to +2% for Orthodox states that have Patriarch Authority.
- Coptic Blessing: +1.5% for Coptic states that have the Send Monks to Establish Monasteries blessing. ( Rights of Man only)
- Building: +3% for a Cathedral
- Decisions: A number of national decisions increase (or decrease) missionary strength.
- Events: Many events give a temporary bonus (or penalty) to missionary strength.
- Province's current religion: +2% in pagan provinces.
- Holy Roman Empire: +1% for being the dominant religion in the Holy Roman Empire
- Estate: +2% in provinces controlled by the clergy estate if clergy loyalty is above 60%.
- Converting religions through the Religion tab gives a +10% "Religious Zeal" bonus for ten years, but only to converting heretics, not heathens.
- Several ideas also affect missionary strength:
In addition, a few ideas specifically affect missionary strength when converting heretics, but have no effect when converting heathens.
Things that decrease this speed include:
- Province's current religion: −2% in Coptic, Muslim and Shinto provinces.
- Province's current religion: −1% in Orthodox and Sikh provinces.
- Culture: −2% for non-accepted cultures.
- Trade company provinces get −100%
- Provincial development: −0.1% for each point of a province development level.
- Religious Centers: Rome, Mecca, the initial Sikh province and all Protestant and Reformed Centers of Reformation get −5%.
- Recently converted provinces get −100%, called Religious Zeal for 30 years.
Centers of reformation
The first three European nations to convert to Protestant, the first three to convert to Reformed, and a British nation if it takes one of the appropriate choices to convert to Anglicanism, have a random European province designated as a Center of Reformation. These centers of reformation will automatically convert nearby provinces to their religion. Provinces converted by a center of reformation get the −100% religious zeal modifier to missionary strength in that province for 30 years. Missionaries can't work in the same province that is being converted by a center of reformation. Each center of reformation can only convert one province at a time. Players will receive a notification if all provinces within the center's range have been converted to its religion.
A center of reformation is destroyed if its province is converted to another religion. The primary method for a Catholic nation to slow or stop the spread of the reformation is to conquer and convert a province with a center of reformation, thereby eliminating its missionary effect on neighboring provinces.
A center of reformation will cease to convert provinces after start of the Age of Absolutism.
Conversion using trade policy
|Available only with the Cradle of Civilization DLC enabled.|
Muslim nations can enable "Propagate religion" policy in trade nodes inside a trade company region, provided that they control at least 50% of trade power in this node. While this policy is active, it will work the same way as a center of reformation.
There are several different ways a country may change religion.
By direct action
Some religions may convert among certain heresies/sects via the Religion panel, at a cost of 100 prestige. This is true for Catholic, Protestant and Reformed Christians, Hindus and Sikhs once Sikhism is unlocked, as well as all Buddhists. Conversion by this method will give a whopping 10% missionary strength against heretics for ten years, making conversion of provinces of the old faith quite rapid, unless it is entirely blocked due to local Religious Zeal modifiers. Sikhs can also convert to Sunni or Shia Islam this way.
Conversion is also possible through decisions in some cases, which causes a -4 stability hit (except for Sikh or Sunni/Shia conversion, which only reduces it by 2). With the Sword and Crescent DLC, Sunni and Shiite (but not Ibadi) Muslims may convert to the other denomination if both their capital and the majority of their province development follows the other denomination. Japanese daimyos, but not the Shogun or Japan itself, may convert to Catholicism by decision if the majority of their territories are Catholic, which can happen following certain events in the 16th century. Pagan nations that are not Tengri may convert to any non-Pagan faith if they control a province of that faith; Tengri nations are limited to Vajrayana Buddhism. Muslims owning a Sikh province may also decide to convert to Sikhism - this decision probably mostly exists to allow Punjab to easily follow its historical religion.
Totemist and Animist pagans get events to convert to Catholic, Protestant, or Reformed Christianity if they have neighbors of the appropriate denomination and a sufficient positive opinion with that neighbor. Tengri pagans with a dominant secondary faith may be prompted to change to it or face a -3 stability hit; they also have event chains that end in conversion to their secondary religion.
A nation in the British region, typically England, can get an event, based on the wives of Henry VIII, to convert to Anglicanism with the Rule Britannia DLC.
Some nations, for example Sweden, have unique events enabling them to change religion.
Countries that have the Indian Sultanate government by default, but are neither Muslim nor were forcefully converted to another religion, will quickly be forced to choose by event between conversion to the appropriate branch of Islam, or facing a large amount of rebels and a stability hit. This generally only is the case if they have been released as a vassal or in a peace deal, which will likely make them Hindu initially, because Indian sultanates rarely convert the local religion, and indeed have no need to due to their large bonus to heathen tolerance. AI will always choose to convert.
Forced conversion by other nations
A nation can force a heretic country to change their state religion as part of a peace deal. The revolutionary target may also do this to heathens. Without an appropriate casus belli such as "Cleansing of Heresy" or "Religious Conformance" (unique to the Holy Roman Emperor against HRE members), this will have the same war score cost as annexing the nation. When a country is converted this way, only the state religion and the capital province's religion change.
Once the religion of the Holy Roman Empire has been locked, the emperor can also request a prince to change their state religion depending on their opinion of the Emperor. Similarly to when forcing a religion of an enemy country, the prince has its capital converted while the rest of the provinces remained unaffected.
With the Common Sense DLC, suzerains may force their subject nations to change religions if they follow a different faith. If heretic, this gives +50 liberty desire, and if heathen +100 liberty desire, both gradually ticking down.
Forced conversion by rebels
Nations can support religious zealots in other countries. These rebels convert a province's religion to the one they represent when occupation is achieved.
Supporting religious zealots is only possible if the desired religion is present in the target nation and is the likely rebel type in a province with unrest above 0. If there are no such provinces in the target nation, one way to achieve it is to sell the target a province of the correct religion.
Generally the nation will be able to overpower the rebels if left to its own devices, so it is critical to support them militarily. This can be done by declaring war against the target nation using the "Support Rebels" casus belli.
A nation that is broken by religious rebels, or that accepts their demands, will convert to the rebels' religion provided that the rebels' religion is the plurality religion in terms of development. For most countries, giving in to religious rebels is the only way to change between religious groups.
However, only Animist rebels, not other types, can convert a non-Pagan nation to a Pagan faith. Thus Animism must serve as a springboard to conversion to other pagan faiths.
- Base missionary strength is very small compared to modifiers, both positive and negative. This means that conversion can be very fast or impossible. Religious ideas are sometimes essential to make any progress conversion work.
- Provinces that do not have the state religion generally suffer from low tolerance and also lower the nation's Religious Unity. With that, nations that are challenged with large numbers of wrong-religion provinces will have to choose between dealing or not dealing with them, and with the 1.26 update the main way of dealing with them as a large nation is to be highly tolerant (usually by using the Humanist idea group).
- Several Triggers for Religions give bonuses or penalties. You should keep in mind these Triggers to optimize your religious conversion. See Triggered modifiers
- See in Static modifiers#Religious unity). (
- See in Static modifiers#Inverse religious unity). (
- See in Static_modifiers#Tolerance). (
- See in Static modifiers#Intolerance). (
- See in Static_modifiers#Active missionary). (
- See patch 1.28.