
Converting from Orthodox to Catholic in Europa Universalis IV can be done through several methods. One way is to have a Catholic vassal, bring them into the fold, and start converting them to Orthodoxy. Then, lower the missionary maintenance and allow revolts to begin, controlling the rebels that pop up. Another method involves having an Orthodox human ally force convert a neighbouring AI One Province Minor (OPM) within Catholic Europe. Once the capital of the OPM is sieged, transfer control of that province to the ally, who will then force convert them to Orthodoxy. The player can then re-siege the OPM and annex them. Additionally, in multiplayer games, a Catholic player can gain an Orthodox province and spawn religious rebels to achieve conversion. It's worth noting that Orthodox Christianity typically cannot convert to other forms of Christianity, and players may need to wait for specific historical events or utilize workarounds, such as playing as a country with the desired religion and sending missionaries.
| Characteristics | Values |
|---|---|
| Orthodox Christianity conversion to Catholicism | Possible via rebels or AI heretic nation |
| Conversion via rebels | Yield to Catholic Zealot rebels by accepting demands or allowing enforcement; stability and prestige will be impacted |
| Conversion via AI heretic nation | Player must have 100% war score against enemy AI by sieging all their provinces, then offer to be converted by the enemy |
| Alternative methods | Have a Catholic vassal and start to convert them to Orthodoxy; control the resulting rebels |
| Alternative methods | Take over Catholic territories, let them take some territories in return, and accept their demands of changing the state religion |
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What You'll Learn

Have a Catholic vassal and convert them to orthodoxy
Converting from Orthodox to Catholic in Europa Universalis IV can be done in several ways. One method is to have a Catholic vassal that can be as large as you, bring them into the fold, and start converting them to Orthodoxy. Here's a detailed guide on how to execute this strategy:
Have a Catholic Vassal
Begin by finding or developing a Catholic vassal that is comparable in size to your nation. This step is crucial as it forms the foundation of your strategy. The larger the Catholic vassal, the more significant their impact on your nation's religion.
Convert Them to Orthodoxy
Once you have established a suitable Catholic vassal, it's time to initiate the conversion process. Start by actively converting them to Orthodoxy. This step may involve sending missionaries or utilizing religious influence. It is important to note that converting a nation requires time and resources, so be prepared for a long-term commitment.
Manage Missionary Maintenance
As you progress with the conversion of your Catholic vassal, intentionally lower your missionary maintenance. This action will stimulate revolts and rebellions within your nation. While it may seem counterintuitive, managing these revolts is a crucial aspect of the strategy.
Control the Rebels
When the rebellions inevitably arise due to the lowered missionary maintenance, exercise control over the rebels. Allow them to complete their siege, but ensure you are present to manage the aftermath. This delicate balance between revolt and control is essential to executing this strategy effectively.
Yield to the Rebels' Demands
After the rebels have completed their siege, it's important to yield to their demands. Accepting their terms will result in a hit to stability and prestige, but it is a necessary step in the conversion process. Ensure that you are attentive during this phase, as neglecting it could lead to undesirable outcomes.
Wait for Catholic Zealots
Following your acceptance of the rebels' demands, the final step is to wait for the emergence of "Catholic Zealot" rebels. These rebels are crucial to your strategy, as their siege of a province will ultimately trigger the switch to the Catholic religion. This process may take some time, so patience is key.
By following these steps, you can effectively convert from Orthodox to Catholic in Europa Universalis IV using the "Have a Catholic Vassal" strategy. Remember that each step requires careful execution and a deep understanding of the game's mechanics.
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Allow Catholic Zealot rebels to enforce demands
Converting from Orthodox to Catholic in Europa Universalis IV can be a tricky process. One way to achieve this is by allowing Catholic Zealot rebels to enforce their demands. Here's a step-by-step guide on how to do this:
Step 1: Acquire Catholic Land
Begin by acquiring some Catholic land. This can be done through various means, such as conquering or purchasing provinces that follow Catholicism. This step is crucial as it provides the foundation for the next steps.
Step 2: Manage Missionary Maintenance
Once you have Catholic provinces, start managing your missionary maintenance. Lower the missionary maintenance in your newly acquired Catholic provinces. This will lead to unrest and eventually revolts as the provinces start converting back to Catholicism.
Step 3: Control the Rebels
As revolts break out, you'll need to carefully manage the rebels. Allow the Catholic Zealot rebels to rise and start sieging your provinces. It's important to let them complete the siege. Remember that these rebels are more likely to appear in provinces that follow their religion, so focus on your newly acquired Catholic territories.
Step 4: Yield to the Rebels
After the Catholic Zealot rebels have completed their siege, you have the option to yield to their demands. Accepting their demands or allowing them to enforce their religion will lead to a switch in the province's religion. This step may impact your stability and prestige, so it's essential to be cautious and manage any potential fallout.
Step 5: Wait for the Effect
Keep in mind that the religious conversion of the province may take some time to occur even after the siege is completed. A short delay is expected, so be patient and allow the process to unfold.
Additional Tips:
- If you're playing as an Orthodox nation, consider joining the Holy Roman Empire (HRE). By joining the HRE, you can achieve religious unity and potentially avoid the need to convert through rebels.
- Alternatively, you could consider converting to Protestantism during the Reformation. This option may save you the hassle of first converting to Catholicism.
- Keep in mind that rebels can be unpredictable, and their behaviour might vary. They may teleport or take some time to move between provinces.
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Join the HRE and accept religious unity
As per the mechanics of the game, Orthodox Christianity cannot be converted to any other kind of Christianity. However, there are some events that allow you to do so. One such event is joining the Holy Roman Empire (HRE). The HRE is a decentralised political power in Central Europe, comprising several member states that act with great autonomy. The power of the Emperor is still considerable, as he has the power to intercede in the wars and affairs of the member states of the Empire. If the Emperor can enact the reforms, he can eventually centralize all the separate nations of the Empire under his own banner, and turn the Holy Roman Empire into a unified powerhouse.
The Emperor can appoint up to twelve Free Imperial Cities, which give the emperor more authority in exchange for trading bonuses. The Emperor can also impose religious unity on the HRE members. If the target is an elector, free city, or Defender of the Faith, they will refuse to convert peacefully, and the Emperor will suffer a prestige hit and gain a casus belli against the target. If the target accepts the request, they convert to the Emperor's state religion and one random province becomes converted automatically. The Emperor suffers a relations hit with other Princes with the heretic religions of all denominations. An appropriate casus belli such as "Cleansing of Heresy" or "Religious Conformance" will lower the cost significantly.
Another way to convert from Orthodox to Catholic is to have a Catholic vassal. Bring them into the fold and start to convert them to Orthodoxy. Next, slide the missionary maintenance down and let the revolts start coming. Control the rebels that pop up and let them complete the siege. You can then wait for Catholic Zealots to pop up and let them enforce their demands. This will result in a hit to stability and prestige.
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Take over Catholic territories and give into their demands
One way to convert from Orthodox to Catholic in Europa Universalis IV (EU4) is to "take over Catholic territories and give into their demands". This strategy involves taking control of Catholic territories and allowing religious rebels to enforce their demands, ultimately leading to a conversion to Catholicism. Here's a detailed guide on how to execute this strategy:
Taking Over Catholic Territories
The first step is to acquire territories that follow the Catholic faith. This can be achieved through various means, such as military conquest, diplomatic negotiations, or strategic alliances. Target Catholic nations or regions that you can feasibly incorporate into your realm. Keep in mind that the size and strength of the Catholic territories you aim to take over will depend on your own nation's capabilities and resources.
Managing Unrest and Rebels
As you take over Catholic territories, it is essential to understand the mechanics of unrest and rebels in EU4. Provinces of non-tolerated religions, such as Catholicism in an Orthodox nation, will have higher unrest. This unrest can lead to the emergence of religious rebels who aim to enforce their religious demands. To facilitate the conversion process, you should allow these religious rebels to flourish and avoid suppressing them. However, be cautious as rebels can break a country prematurely if they control more than 50% of the country or have controlled the capital for an extended period (typically 24 months).
Controlling the Rebels
While allowing religious rebels to operate, it is crucial to control and protect them. Set your vassals to "snooze" within your territories to avoid accidental engagements with the rebels. Ensure that allies or other armies do not have access to your country during this time, as they might inadvertently fight the rebels. Manage your borders and straits to prevent rebels from wandering into neighbouring countries, where they could be destroyed.
Yielding to Rebel Demands
Once the Catholic religious rebels have gained a foothold and controlled a significant portion of your country, you can start thinking about yielding to their demands. The rebels' demands will include changing the state religion to Catholicism. By accepting their demands or allowing them to enforce their will, you will initiate the process of converting your nation from Orthodox to Catholic. Keep in mind that yielding to rebel demands may result in a temporary hit to stability and prestige, so time this step carefully.
Post-Conversion Considerations
After successfully converting to Catholicism, there are a few additional considerations. You may now have better diplomatic relations with other Catholic nations, so consider forming alliances or exploiting this improved relationship for strategic gains. Additionally, keep an eye on religious leagues and the potential declaration of Catholicism as the official faith of the Holy Roman Empire (HRE). Joining the HRE as a Catholic nation can provide benefits, such as accepting religious unity.
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Convert by being forced to by an AI heretic nation
Converting from Orthodox to Catholic in Europa Universalis IV can be achieved through various methods, one of which involves being forced to convert by an AI heretic nation. Here is a step-by-step guide on how to accomplish this:
First, it is essential to understand that this method involves interacting with another AI nation that follows a heretical branch of your current faith. In your case, as you are looking to convert from Orthodox to Catholic, you would need to interact with a Catholic nation.
To initiate the process, start a war with the desired Catholic nation and aim to achieve a 100% war score against them by sieging all their provinces. It is crucial that your overall country size is less than the 100% war score you have achieved against the enemy AI.
Once you have achieved the desired war score, instead of demanding concessions from the enemy AI, you will offer yourself to be force-converted to their religion as part of the peace deal. This is done through the subject interaction screen, where you can propose your nation's conversion to Catholicism.
It is important to note that this method relies on the specific mechanics of the game, where you can only forcibly convert heretics, who are nations following a different faith within the same denominational group. In this case, Orthodox and Catholic are both forms of Christianity, making this strategy applicable.
Additionally, keep in mind that this method may not always be available, depending on the circumstances and mechanics of the game. For instance, some religions, like Judaism, do not have the option to forcibly convert other nations. Furthermore, primitive nations cannot perform such "reverse" force conversions until they are reformed.
By following these steps and understanding the underlying mechanics, you can successfully convert from Orthodox to Catholic by being forced to do so by an AI heretic nation in Europa Universalis IV.
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Frequently asked questions
There are a few ways to convert from Orthodox to Catholic in Europa Universalis IV. One way is to have a Catholic vassal, bring them into the fold, and start to convert them to Orthodoxy. Then, lower your missionary maintenance and allow revolts to begin. Control the rebels that pop up and let them complete the siege.
You can get Catholic zealots to help you convert by having an Orthodox human ally force convert a neighbouring AI One Province Minor (OPM) within Catholic Europe. Once the capital of the OPM has been sieged, transfer control of that province to your ally. Your ally can then force convert them to being Orthodox, and you can annex them fully. From there, you can spawn religious rebels to convert your country.
Yes, you can wait for the reformation and then take religious zealot Protestant lands, saving yourself the hassle of being Catholic. You can also play as a country with the desired religion, send missionaries to convert the target, and then switch to playing the target.
Yes, you can switch your state religion through the administrative tab and the religious tab.
Converting to Catholicism can help you gain allies, as nations of mutually accepted religions have a better chance of reaching agreements with one another.









































