Diplomacy Guide
Master international relations in Europa Universalis V - alliances, vassals, and coalition management
Alliance Systems
Alliances are your primary defense against aggression. Choose allies wisely based on their strength and your strategic goals.
🤝 Forming Alliances
- • Improve relations to +100 or higher
- • Check alliance acceptance tooltip
- • Royal marriages boost acceptance
- • Common rivals increase acceptance
- • Distance and size affect willingness
⚠️ Alliance Considerations
- • Allies can drag you into wars
- • Breaking alliances costs stability
- • Great powers have limited ally slots
- • Check ally's other alliances
- • Consider ally's military strength
💡 Pro Tip
Ally nations that share your rivals but won't compete for the same expansion targets. This maximizes defensive value while minimizing conflicts of interest.
Vassalization
Vassals provide military support and can be diplomatically annexed. They're an efficient way to expand without direct conquest.
Diplomatic Vassalization
Offer vassalization to small nations. Requires high relations and significant power difference.
Force Vassalization
Demand vassalization in peace deals. Costs more warscore but bypasses diplomatic requirements.
Annexation
After 10 years, you can begin annexing vassals. Requires high relations and diplomatic points.
Vassal Benefits
- • Provide troops in your wars
- • Pay you a portion of their income
- • Can be fed conquered provinces
- • Reconquest CB for their cores (low AE)
- • No direct governing cost
- • Buffer states for defense
Coalitions & Aggressive Expansion
Aggressive Expansion (AE) is the opinion penalty other nations get when you conquer territory. Too much AE triggers coalitions - defensive alliances against you.
📊 AE Factors
🛡️ Coalition Prevention
- • Keep AE below 50 with major powers
- • Improve relations with outraged nations
- • Expand in different directions
- • Wait for AE to decay (2/year base)
- • Use claims to reduce AE
Coalition Warning
Nations with -50 or worse opinion from AE can join coalitions. A coalition war against you means fighting multiple nations at once. Avoid at all costs in early game!
Royal Marriages & Personal Unions
💒 Royal Marriages
- • +25 relations with married nation
- • Increases alliance acceptance
- • Chance for Personal Union on ruler death
- • Breaking marriage = -1 stability
- • Only available to monarchies
👑 Personal Unions
- • Junior partner under your dynasty
- • They fight in your wars
- • Can be inherited after 50 years
- • Claim throne CB if same dynasty
- • Most powerful diplomatic tool
Key Diplomatic Actions
Improve Relations
Cost: Diplomat
Increase opinion over time. Essential for alliances and preventing coalitions.
Fabricate Claim
Cost: Diplomat + 20 spy network
Create casus belli for conquest. Reduces AE and warscore cost.
Support Independence
Cost: Diplomat
Help subjects break free. Gain a grateful ally.
Guarantee
Cost: Diplomat
Protect a nation from attack. Useful for blocking rivals.
Subsidies
Cost: Monthly ducats
Pay another nation monthly. Improves relations and helps allies in wars.
Sell Province
Cost: Province
Transfer province for gold. Useful for reducing overextension.
📖 Related Guides
Diplomacy Discussion
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