In Europa Universalis IV, few nations carry the same historical weight and legendary ambition as Byzantium. Starting as a weakened remnant of the Eastern Roman Empire, players who choose Byzantium often pursue grand restoration goals, from reconquering the old Roman lands to restoring Orthodoxy to its former glory. One of the more complex and lore-rich decisions available to a resurgent Byzantine Empire is the ‘Union of Churches’ event. This decision, steeped in religious and political significance, can reshape your empire’s path and its interactions with the Catholic and Orthodox worlds. Understanding the mechanics, consequences, and strategic implications of the Union of Churches in EU4 is essential for any player looking to dominate as Byzantium.
The Historical and Religious Context
Background of the Union of Churches
The Union of Churches refers to a historical attempt to heal the schism between the Roman Catholic and Eastern Orthodox Churches. In real history, the Council of Florence (1439) aimed to unite the two branches of Christianity under papal authority. For Byzantium in EU4, the event is reimagined as a critical choice that blends theology with realpolitik, allowing the emperor to embrace Catholicism in exchange for diplomatic and military opportunities often at the cost of religious unity within the empire.
Religious Tensions in Byzantium
When playing as Byzantium in EU4, your nation starts as Orthodox Christian surrounded by hostile Sunni and Catholic powers. While Orthodoxy offers unique mechanics such as Patriarch Authority and Metropolitans, it lacks the global diplomatic benefits enjoyed by Catholic nations, especially those tied to the Holy See. The Union of Churches offers a path to potentially stronger alliances and papal favor, but at significant cost to internal stability and identity.
How to Trigger the Union of Churches
Conditions and Requirements
The Union of Churches decision in EU4 is not available by default. To unlock this decision, you must meet the following conditions:
- You must be playing as the Byzantine Empire (tag: BYZ).
- Your country must be Orthodox.
- The Papal States must exist and be Catholic.
- Your nation must be stable enough to enact major reforms (usually meaning positive stability and no recent major rebellions).
- You must not already be Catholic or have enacted the decision previously.
Once these criteria are met, you will see the option to form the Union of Churches in your decisions tab, triggering an important fork in your religious path.
Effects of the Union of Churches Decision
Immediate Outcomes
Upon choosing to enact the Union of Churches, the following consequences are applied:
- Your religion changes from Orthodox to Catholic.
- All Orthodox provinces gain a significant penalty to religious unity (due to heresy).
- You lose all Patriarch Authority and Orthodoxy-specific benefits.
- You gain access to the Papal Curia system and the potential to become the Papal Controller.
- You may improve relations with Catholic nations, especially the Papal States and major Western European powers.
While this can immediately boost your diplomatic standing, it also makes you vulnerable to religious revolts and reduced income from Orthodox provinces until you can convert them or stabilize the realm.
Long-Term Strategic Implications
In the long term, the Union of Churches opens new doors. You can more easily ally with powerful Catholic nations like Austria, France, or Spain, and you can benefit from Catholic events and papal bonuses. However, unless you invest heavily in converting your provinces, you may suffer from reduced unity and persistent unrest. Balancing short-term instability with long-term gains is the key challenge when making this decision.
Strategic Considerations for Byzantium
When to Take the Union
The best time to take the Union of Churches is after you’ve secured your early survival, typically once you’ve pushed back the Ottomans, regained control of Constantinople, and have solid military and economic footing. Taking the Union too early may cripple your internal stability and open you up to rebellion. After stabilizing your core territory, the diplomatic advantages of becoming Catholic can help you expand westward or defend against powerful European rivals.
Alternatives to the Union of Churches
Some players may prefer to remain Orthodox and leverage Patriarch Authority for its manpower and unrest bonuses. By spreading Orthodoxy and building strong national ideas around religious unity, it’s possible to remain a highly effective Orthodox powerhouse. You may also convert Catholic nations by force or use Religious ideas to expand into Muslim territories more effectively. The Union of Churches is not mandatory to succeed, but it offers a different flavor and route for imperial growth.
Gameplay Tips for Managing the Transition
Stabilizing After Conversion
After enacting the Union, your primary goal should be stabilizing your empire. This involves:
- Raising your stability to +2 or +3 to minimize unrest.
- Boosting your missionary strength through Religious ideas or advisers.
- Focusing on converting your most rebellious Orthodox provinces first.
- Using autonomy strategically to lower unrest until conversions are complete.
It may take several decades to fully convert your empire, but the improved diplomacy and papal interactions can make it worthwhile.
Leveraging Papal Influence
As a Catholic nation, you now generate Papal Influence based on your number of Catholic provinces and church power. Use this influence to become Papal Controller when possible, giving you bonuses to diplomats, stability, and even free claims. These bonuses are particularly valuable during wars with Muslim nations or during European diplomacy where legitimacy and prestige are essential.
Roleplaying and Flavor
Immersion and Narrative
For players who enjoy immersive, lore-based campaigns, the Union of Churches offers a dramatic narrative shift. You can roleplay a pragmatic emperor choosing unity over tradition to save the empire, or a controversial ruler risking rebellion to modernize and westernize Byzantium. This decision adds emotional weight to your campaign and makes internal politics just as engaging as external conquest.
Impact on National Identity
Adopting Catholicism often distances Byzantium from its Orthodox heritage. Some players may feel it betrays the spirit of the Eastern Roman Empire. Others see it as a tactical move that echoes historical desperation. Either way, the choice is rich with consequences, both mechanical and symbolic, enhancing the depth of any Byzantium run.
The Union of Churches in Europa Universalis IV represents a major crossroads for the Byzantine Empire. It forces players to weigh tradition against opportunity, stability against diplomacy, and identity against power. Whether you embrace Catholicism to unlock new alliances and influence in Western Europe or remain a bastion of Orthodoxy resisting outside pressure, the path you choose shapes the destiny of your empire. Mastering the mechanics and timing of this decision is crucial for any player seeking to rewrite history and restore Byzantium to its rightful glory.