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File:Diplomatic interface other.png
The diplomacy interface, as the player England, viewing Scotland

Diplomacy in EU4 operates using a bilateral system. For example, the player country may have positive relations with another country while that country might have negative relations with the player. Relations can be increased by having alliances, being in the same coalition, fighting a common war, having a common rival, decisions, events and placing a diplomat in their capital. Relations are decreased by declaring war, being rivals, sending insults, having a different religion, breaking/dishonoring an alliance, events and decisions.

Reasons for a nation liking/hating another are displayed in tooltips wherever opinion is shown. The total is capped at +200/-200.

Diplomacy is conducted by diplomats, and the diplomatic options available to diplomats depends on a country's technology and ideas. Diplomatic options are split in seven categories: alliance, influence, relations, dynastic, covert, economy and access. The emperor of the Holy Roman Empire has an extra category: emperor actions. The Papal controller has an extra category: Papal actions. The declare war and sue for peace diplomatic options are found outside of these categories.



A diplomat is required to perform most diplomatic actions. Some actions - improving relations, annexing a vassal, and all covert activities - will tie up a diplomat until the task is completed, although they may be recalled earlier. Actions that will tie up a diplomat will display a diplomat icon (Diplomat.png) on their button. Other actions are immediate. After completing a mission, a diplomat will be unavailable while he travels back home, which can take anywhere from a few days to several months depending on the distance between one's capital and that of the target country. The precise travel speed of diplomats is 20 distance per day.

Gaining diplomats

Each country starts with 2 Diplomat.png diplomats by default. The following give more:

Diplomat.png Traditions Ideas Bonuses Policies
  • Aachen traditions
  • Ajami traditions
  • Hausan traditions
  • Kurdish traditions
  • Mori traditions
  • Samtskhe traditions
  • Sligonian traditions
  • Thüringian traditions
  • Westphalian traditions
  • Aristocratic idea 6: International Nobility
  • Diplomatic idea 1: Foreign Embassies
  • Diplomatic idea 3: Grand Banquets
  • Espionage idea 2: Agent Training
  • Aq Qoyunlu idea 5: Expansive Diplomacy
  • Assamese idea 7: Ahom Diplomacy
  • Asturian idea 3: Asturian Aristocracy
  • Ayutthayan idea 4: Embassies
  • Baden idea 3: Active Diplomacy
  • Bosnian idea 6: Flexible Diplomacy
  • Butuan idea 7: Long Range Diplomacy
  • Cherokee idea 7: Cherokee Emperor
  • Chagatai idea 6: Scheming Nobility
  • Cilli idea 3: Political Maneuvering
  • Circassian idea 6: Steppe Diplomats
  • Gelre idea 1: Feudal Elevation
  • Iroquois idea 4: Keepers of the Fire
  • Karamanid idea 4: Seize the Opportunity
  • Krakowian idea 7: The Free City
  • Lorraine idea 4: Flexible Diplomacy
  • Luxembourg idea 7: Rivals On All Sides
  • Manx idea 1: The Stanleys
  • Medri Bahri idea 3: Diplomatic Flexibility
  • Moluccan idea 7: Pragmatic Diplomacy
  • Mushasha idea 6: Outward Pragmatism
  • Nanbu idea 3: Connection With Kyoto
  • Odoyev idea 2: Dynamic Diplomacy
  • Ragusan idea 3: Patronage
  • Rostov idea 6: Political Influence
  • Saxon idea 1: Albertine and Ernestine lines
  • Shawnee idea 6: Far−Reaching Relations
  • Shiba idea 3: Consolidation of the Kanrei Position
  • Shoni idea 3: Diplomacy through Tsushima
  • Siddi idea 5: Siddi Diplomacy
  • Trebizondian idea 4: Komnenoi Princesses
  • Tyrone idea 5: Catholic Diplomacy
  • Utsunomiya idea 1: Fujiwara Descendant
  • Venetian idea 2: Printing Industry
  • Vijayanagar idea 6: Adroit Diplomacy
  • Yamana idea 1: Descendant of Nitta
  • Yemeni idea 7: Foreign Embassies
  • Antemoro ambition
  • Mapuche ambition
  • West African ambition
  • Administrative-Diplomatic: The Recordkeeping Act
  • Diplomatic-Aristocratic: The Tenures Abolition Act
  • Diplomatic-Defensive: The Diplomatic Defense Act
  • Espionage-Economic: The Foreign Support Act
  • Espionage-Offensive: The Black Chamber Act
  • Innovative-Espionage: The Espionage Act

Diplomat.png Triggers

Diplomatic relations.pngDiplomatic relations cap

A nation may only form diplomatic agreements with a limited number of other nations before overextending its diplomatic corps. Each relation over the cap costs 1Diplomatic power.png diplomatic monarch point per month. The limit is on the number of countries, not the number of deals, so having multiple agreements with a single nation only counts once.

Agreements that count towards the cap include:

  • Alliances
  • Royal marriages
  • Guarantees
  • Having a vassal or junior PU partner
  • Getting military access
  • Supporting independence
  • Transferring trade power (including enforced 'transfer trade' as part of peace agreement)

Agreements that do NOT count toward the cap include:

  • Giving military access
  • Getting or giving fleet basing rights
  • Getting or giving loans
  • Coalitions
  • Federations
  • Embargoes
  • Warnings
  • Giving subsidies
  • Having a colonial subject, protectorate or client state
  • War reparations
  • Vassals of the Holy Roman Emperor who are members of the empire, if the third to last imperial reform has been passed

Increasing the diplomatic relations cap

The base for each country is 4 diplomatic relations.[1] It is affected by the following:

Diplomatic relations.png Conditions
+4 Shogunate government
-2 Duchy rank Tribal government Duchy

Ideas and policies:

Diplomatic relations.png Traditions Ideas Bonuses Policies
  • Provençal idea 5: Public Weal
  • Antemoro traditions
  • Brunswicker traditions
  • Burgundian traditions
  • Isshiki traditions
  • Jaunpuri traditions
  • Ladakh traditions
  • Kiwi traditions
  • Milanese traditions
  • Muscovite traditions
  • Nubian traditions
  • Palatine traditions
  • Savoyard traditions
  • Timurid traditions
  • Diplomatic idea 2: Cabinet
  • Expansion idea 5: Additional Diplomats
  • Influence idea 4: Buffer States
  • Asakura idea 1: Hidden Diplomacy
  • Austrian idea 6: Austrian Court
  • Berber idea 6: Dual Diplomacy
  • Bosnian idea 4: Italian Connections
  • Butuan idea 1: Indianized Society
  • Colognian idea 6: Shifting Alliances
  • Danziger idea 1: Danzig Law
  • Desmondian idea 5: Fierce Independence
  • English idea 3: Secretaries of State
  • French idea 1: French Language in All Courts
  • French ducal idea 6: French Enlightenment
  • German idea 6: Thurn und Taxis
  • Goslar idea 7: Joining the Leagues
  • Greek idea 6: Philhellenism
  • Hanoverian idea 6: Hanoverian Chancery
  • Hausan idea 1: Heirs of Bayajida
  • Herzegovinian idea 7: Shifting Allegiances
  • Hormuz idea 4: Far-reaching Diplomacy
  • Imagawa idea 5: Triple Alliance
  • Italian idea 6: Italian Diplomacy
  • Knights Hospitaller idea 3: The Tongues of Knights
  • Krakowian idea 7: The Free City
  • Kurdish idea 4: Active Diplomacy
  • Lan Na idea 7: Dynastic Spread
  • Leinster idea 6: The Geraldine League
  • Lur idea 7: Foreign Trade Ties
  • Luxembourg idea 6: The Grand Duchy of Luxembourg
  • Lüneburger idea 6: Adroit Diplomacy
  • Manipur idea 6: Bengali Influence
  • Mantuan idea 6: Mantuan Royal Ties
  • Mazovian idea 3: Between Monk, Eagle and Purse
  • Mori idea 3: Diplomatic Intrigues
  • Orleanaise idea 7: French Language in All Courts
  • Polotskian idea 6: Diplomatic Initiative
  • Québécois idea 3: Relations with the First Nations People
  • Sardinian-Piedmontese idea 1: Diplomatic Flexibility
  • Satake idea 5: Eastern Coalitions
  • Saxon idea 5: Corpus Evangelicorum
  • Swabian idea 4: The Swabian League
  • Swahili idea 7: Familiar Presence Abroad
  • Three Leagues idea 1: The League System
  • Thüringian idea 7: Expansive Marriage Policy
  • Transylvanian idea 7: Anti-Habsburg Policies
  • Tunisian idea 2: Dual Diplomacy
  • Wurzburgian idea 1: Legacy of the Imperial Diets
  • Uesugi idea 1: Kanto Kanrei
  • Ulmer idea 2: Schwäbischer Bund
  • Yamana idea 3: Mediate Succession Disputes
  • Aachen ambition
  • Ajami ambition
  • Imperial German ambition
  • Kikuchi ambition
  • Kuban ambition
  • Mossi ambition
  • Native ambition
  • Diplomatic-Defensive: The Diplomatic Defense Act
  • Humanist-Influence: The Foreign Aid Act
  • Influence-Offensive: Foreign Conscription Centers

Certain events give a temporary increase in the relations cap.

Diplomatic reputation.pngDiplomatic reputation

A nation's diplomatic reputation represents its overall diplomatic ability and credibility; it replaces the diplomatic skill of EU3. Diplomatic reputation is visible in the diplomacy window of one's own country.


Each point of diplomatic reputation gives a +5% chance to inherit lesser partner in a personal union, +1 Diplomatic power.png diplomatic power used per month while annexing vassals or union partners, -3% to the Liberty desire.png liberty desire of all subject nations, and the following bonuses to other countries accepting diplomatic proposals:

Action Bonus
Offer Alliance 5
Offensive Call to Arms 5
Royal Marriage 5
Offer Vassalization 3
Transfer Trade Power 3
Ask for Military Access 3
Ask for Fleet Basing Rights 3

Gaining diplomatic reputation

The following modifiers increase diplomatic reputation:

Diplomatic reputation.png Traditions Ideas Bonuses Policies
  • Holy Roman traditions
  • Diplomatic idea 5: Experienced Diplomats
  • Influence idea 5: Diplomatic Influence
  • Aachen idea 7: Congresses of Aachen
  • Austrian idea 4: Habsburg Dominance
  • Kiwi idea 7: Pokarekare Ana
  • Roman idea 2: Legacy of Rome
  • Jerusalem idea 7: Cosmopolitan Nobility
  • Ansbach traditions
  • Cilli traditions
  • Date traditions
  • Delhian traditions
  • French traditions
  • Goslar traditions
  • Hessian traditions
  • Iroquois traditions
  • Novgorodian traditions
  • Odoyev traditions
  • Papal traditions
  • Provençal traditions
  • Rajput traditions
  • Ryukyuan traditions
  • Silesian traditions
  • Sukhothai traditions
  • Yamana traditions
  • Afghan idea 4: Afghan Diaspora
  • Ajami idea 4: Persian Language and Court Culture
  • Antemoro idea 4: Ombiasa
  • Arakanese idea 5: Buddhist Sultans
  • Arawak idea 6: Enemy Of My Enemy
  • Armenian idea 3: Border Nation
  • Athenian idea 3: Athenian Pragmatism
  • Ava idea 6: Keep the Shan in Line
  • Bahmani idea 5: Takht-e-Firoza
  • Barbary Corsair idea 4: Mazmorras
  • Bayreuther idea 1: Hohenzollern Margrave
  • Berg idea 4: The Seat of the Electorate
  • Betsimisaraka idea 7: European Diplomacy
  • Brandenburg idea 5: Seat of the Old Emperors
  • Bremish idea 1: Lex Saxonum
  • Breton idea 6: League of the Public Weal
  • Brunswicker idea 1: The Welfian Dynasty
  • Butuan idea 4: Butuan Goldwork
  • Castilian idea 5: Infantas
  • Chachapoyan idea 4: Women Diplomacy
  • Chiba idea 1: Taira Lineage
  • Chinese idea 7: Middle Kingdom
  • Clevian idea 4: Strategic Marriages
  • Creek idea 6: Muscogee Neutrality
  • Cypriot idea 4: Lusignan Diplomacy
  • Deccani idea 6: Jewels of the Nizams
  • Dhundhari idea 2: Seek the Protection of Great Powers
  • Dortmund idea 4: The Emperor's Favorite
  • Ethiopian idea 4: Diplomatic Demeanor
  • Ferraran idea 4: Margraves of Este
  • Frankfurter idea 2: Seat of Imperial Elections and Coronations
  • Genevan idea 2: Neutral Grounds
  • Georgian idea 7: Georgian Embassies
  • German idea 3: Reichskreis
  • Great Shun idea 2: The Dashing King
  • Greek idea 6: Philhellenism
  • Gujarati Princedom idea 4: Rajput Dynasties
  • Herzegovinian idea 4: Accommodation with the Ottoman Turks
  • Holstein idea 2: Between a Kingdom and the Empire
  • Hormuz idea 4: Far-reaching Diplomacy
  • Huron idea 5: Missionary Welcome
  • Isshiki idea 3: Bridge of Heaven
  • Khorasani idea 1: Land of the Rising Sun
  • Kievan idea 2: Heritage of the Rus'
  • Kildarean idea 1: Lords Deputy
  • Kitabatake idea 3: Supporters of the Emperor
  • Kongo idea 4: Diplomacy With European Monarchs
  • K'iche idea 4: The Ball Game
  • Liège idea 5: The Prince-Bishop's Palace
  • Luban idea 7: Prestige of the Mulopwe
  • Luxembourg idea 1: Imperial Legacy
  • Lüneburger idea 2: The Welfian Dynasty
  • Manipur idea 7: Far-Reaching Diplomacy
  • Mantuan idea 1: Free Imperial City of Mantua
  • Mapuche idea 6: Peace Parliaments
  • Maravi idea 2: Mlira Cult
  • Meath idea 2: Foreign Nationals
  • Mesoamerican idea 3: The Ball Game
  • Montferrat idea 1: Cousins to Kings and Emperors
  • Moravian idea 1: Margraviate of Moravia
  • Muscovite idea 7: Descendants of Byzantine Emperors
  • Münster idea 4: Cities of peace
  • Mysorean idea 7: Dynamic Diplomacy
  • Nepali idea 1: The Divya Upadesh
  • Ormond idea 2: The Courts of Europe
  • Ouchi idea 1: Descendant of Baekje
  • Pacific Northwest idea 3: Totem Poles
  • Palatinate idea 1: Imperial Vicar and Archsteward
  • Pegu idea 7: Mon Diaspora
  • Rigan idea 5: Free City of Riga
  • Saxon idea 3: The Zwinger
  • Shoni idea 1: Vice-Minister of Dazai-fu
  • Sinhalese idea 4: Centre of Learning
  • So idea 5: Tough Negotiators
  • Swahili idea 7: Familiar Presence Abroad
  • Theodorian idea 3: Russian Aristocracy
  • Thomondian idea 1: Fierce Rivalry
  • Three Leagues idea 3: The Grey League
  • Tibetan idea 5: Potala Palace
  • Trebizondian idea 4: Komnenoi Princesses
  • Ulster idea 3: Civilist of the Irishry
  • Urbinate idea 5: The Book of the Courtier
  • Vindhyan idea 1: Rajput Connections
  • Wallachian idea 1: Cunning Diplomacy
  • West Indies idea 6: Interconnected Relations
  • Wurzburgian idea 2: Duke in Franconia
  • Yarkandi idea 3: Tarikh-i-Rashidi
  • Yaroslavlyian idea 2: Third Option
  • Assamese ambition
  • Epirote ambition
  • Medri Bahri ambition
  • Nuremberger ambition
  • Pisan ambition
  • Rostov ambition
  • Sadiyan ambition
  • Tirhuti ambition
  • Diplomatic-Expansion: Commercial Embassies
  • Diplomatic-Offensive: The Underhanded Diplomacy Act
  • Diplomatic-Quality: Professional Diplomatic Corps
  • Diplomatic-Quantity: The Pen Relies on The Sword Act
  • Humanist-Influence: The Foreign Aid Act
  • Innovative-Diplomatic: The Diplomatic Cooperation
  • Legitimacy.png Legitimacy: -1 to +1
  • Overextension.png Overextension: -2 per 100%
  • Trading in Ivory.png Ivory: +1
  • Statesman advisor: +1
  • Annexed Vassals: -3 for 10 years
  • Institute Reichsregiment (HRE reform): +1 for the Emperor
  • Having Ganesha as patron deity (as Hindu): +1
  • Buddhist state with balanced karma: +1
  • Reformed state with stability focus: +1
  • Tengri state with Catholic syncretic faith: +1


See also: Warfare

Declare war

This will declare war on the target country. See warfare for more information on wars.

Casus belli

Main article: Casus belli

A reason for war, each casus belli represents a valid reason for one country to declare war on another. A casus belli is required to avoid a stability drop when declaring war. Valid casus belli include:

  • Reconquest (Take some land where the country has a core)
  • Conquest (Take some land where the country has a claim)
  • Claim Throne (The ruler has a chance to force a personal union if the target nation heir has a weak claim or if there is no heir, provided the country has a royal marriage and has the same dynasty)
  • Diplomatic Insult (They have insulted the country)
  • Trade Dispute (They have embargoed the country (and the country hasn't embargoed them), or both countries are merchant republics)
  • Trade Conflict (Both countries are competing for dominance in a trade node)
  • Coalition (The target has at least -50 aggressive expansion towards the attackers, who have formed a coalition against them. Can only take or return cores)
  • Colonialism (Take an enemy's colonies near the country's own)
  • Support Rebels (When supporting rebels, the country can get this casus belli to declare war on its foe and enforce the rebels' demands)

Sue for peace

Main article: Ending a war

This option will open the peace negotiation screen where the player will negotiate their demands, the terms of their surrender or simply a white peace. The leader of each war alliance can make peace separately with each independent country on the other side (except any that joined as part of a coalition), in which case only individual warscore against that country and its subjects is taken into account (battles only count towards overall score). This can be essential to get the desired peace deal - the overall warscore may be lower than against a single participant, so the player can get more out of the war by picking off participants one by one.

Call to arms

See also: Alliance

Ask an ally to join a war. This action does not require a diplomat. An ally called into a war cannot call in his allies, unless it is a defensive war and the ally was named a co-belligerent by the attacker (note that the Emperor defending the empire and coalition members are always considered co-belligerents). The factors that influence an AI nation's proclivity for accepting a call to arms are

Factor Effect
Caller diplomatic skill +2 per ruler Diplomatic power.png diplomatic skill
Caller diplomatic reputation Positive: +5 per point
Negative: -5 per negative point
Trust Positive: +1 per point
Negative: -1 per point
Attitude towards caller (on offense) Defensive attitude Defensive: -30
Threatened attitude Threatened: -120
Hostile attitude Hostile: -150
Attitude towards caller (on defense) Hostile attitude Hostile: -20
Threatened attitude Threatened: -20
Attitude towards enemy (on offense) Rivalry attitude Rivalry: +40
Hostile attitude Hostile: +20
Neutral attitude Neutral: 0
Unknown attitude Unknown: 0
Threatened attitude Threatened: -40
Friendly attitude Friendly: -60
Attitude towards enemy (on defense) Neutral attitude Neutral: 0
Friendly attitude Friendly: -20
Defender is part of the empire and nation is the emperor
(calling emperor to defend HRE member)
Defensive war +30
Would be called into multiple wars -1000
Allied with target in another war -1000
Fighting in another war together -1000
Has a truce with enemy -1000
Nation is allied with target -1000
Not willing to join another offensive war until date -1000
Nation is the Holy Roman Emperor
(calling emperor against HRE member)
Emperor's opinion about HRE member (on defense) Negative: -1 per point
Accepting would destabilize nation -50 per point of Icon stability.png stability hit
Nation is in debt Offensive call to arms: -10 per month of income needed to pay off all loans
Defensive call to arms:
Defender of the Faith call to arms:
Fighting in another war -20
War exhaustion -10 per point
Manpower low
Army strength low
Distant war

†: Actual monthly income may differ from amount reported in ledger

Among the factors that influence the AI's behavior above, nation is in debt is generally the easiest one for human players to manipulate. If an AI ally is reluctant to join a war due to debt, establishing a maximum subsidy can significantly reduce this negative factor once the ledger registers the increased income. This allows one to quickly drag the AI ally into war, and the subsidy can be cancelled immediately if there is no concern over the ally's war enthusiasm. Sending a gift before establishing the subsidy may be helpful as well, though there is no guarantee that the AI will use the gift to pay down its debt.

Alliance actions

See also: Alliance

Offer alliance

Propose to form an alliance with the target nation. Both nations must have a positive opinion of the other one.

AI nations will only accept alliance offers if they have more positive than negative reasons for doing so:

Factor Effect
Proposer army strength +20 max
-20 min
Proposer navy strength
(if target nation borders any sea)
+10 max
-10 min
Attitude towards proposer Friendly attitude Friendly: +50
Protective attitude Protective: +50
Threatened attitude Threatened: +20
Neutral attitude Neutral: -20
Hostile attitude Hostile: -100
Rivalry attitude Rivalry: -130
Common rival +10
Nation's opinion about proposer +0.25 per positive relation
Trust +0.5 per point
Allied to proposer's rival -50
Proposer allied to rival -50
Proposer diplomatic reputation +5 per positive point
-5 per negative point
Proposer is at war -1000 per offensive war, -50 per defensive war
Not the same religious group -20
Distance between borders
(only if attitude is neutral)
-0.2 per distance between borders greater than 30
Proposer is threatened by nation's rival +20
Proposer already has a powerful ally -50

†: Distance between borders can only be seen in debug mode. It is possible to estimate distances using the fact that diplomats travel at a speed of 20 distance per day between capitals.

Dissolve alliance

Dissolves an alliance with the target country if one exists. Performing this action during peace time will lower relations by -50 with said country. Breaking an alliance during wartime will incur an additional Icon stability.png -2 stability hit on top of the relation penalty.

Coalition.png Form/join coalition

Main article: Alliances#Coalition

Coalitions are special alliances directed against a particularly threatening nation. AI nations will only join coalitions against nations that have incurred large amounts of Aggressive expansion impact.png aggressive expansion. If the coalition target declares war on a coalition member, all members automatically join the war, even if they have a truce with the target. In an offensive war against the target, all members without truces join. Members of coalitions cannot sign separate peaces. A nation may only be in one coalition at a time. Nations cannot belong to a coalition against a nation they have a truce with.

Invite to Federation

Federations are multilateral defensive alliances available only to natives with the tribal council government. If a federation member is attacked, all members are called in. Federations are not mutually exclusive with regular alliances. The leader of a federation gets a bonus to diplomatic reputation and morale.

Support independence

Join the independence war of the target country's side if this country as a subject declares war against its overlord. The target must accept the offer of independence, and is unlikely to do so if it likes its overlord. If war breaks out, the support is converted to a regular alliance for the duration of the war.

Influence actions

Enforce peace

Demand that the leading attacker in a war make peace with the leading defender. Refusal will bring the player into the war on the side of the defender. The following conditions must be met in order to enforce peace:

  • The player must not have a truce with the leading attacker.
  • The player must have at least +100 relations with the leading defender.
  • The attacker must have -25% warscore or better.

Enforce peace is a useful method for entering wars at the player's discretion without triggering any automatic defensive call to arms from the opponent. European powers outside the Holy Roman Empire can use enforce peace on empire members to enter wars against them without drawing the emperor's wrath for example.

Offer vassalization

Main article: Vassal

Attempt to peacefully vassalize the target country. The requirements are:

  1. Must have at least +190 relations with the target country.
  2. Must be allied to the target country.
  3. Target country must be at peace.
  4. The tech group difference between the player and the target country must be less than 50% (otherwise the target can be made a protectorate instead).
  5. The target is willing to accept vassalization. See the vassal page for details.

The factors that influence an AI nation's desire to accept a vassalization offer are:

Factor Effect
Attitude towards proposer Friendly attitude Friendly: +10
Threatened attitude Threatened: +10
Neutral attitude Neutral: -20
Hostile attitude Hostile: -100
Outraged attitude Outraged: -100
We have a royal marriage +10
Trust +0.2 per positive point
Proposer diplomatic reputation +3 per positive point
-3 per negative point
Difference in government ranks +10 per difference in rank
Nation has a religion not in the same religious group -20
Nation has a different religion withing the same religious group -10
Nation is a merchant republic -30
Proposer is a merchant republic -30
Nation is member of the empire -20 if proposer is also member
-30 if proposer is not member
Nation is an elector -1000
Nation has vassals of their own -1000
Nation is the Papal State -1000
Distance between borders -0.5 per distance between borders
Nation has more than 100 total development -1000

†: Distance between borders can only be seen in debug mode. It is possible to estimate distances using the fact that diplomats travel at a speed of 20 distance per day between capitals.

Break vassalization

Free a vassal as an independent nation. Costs Prestige.png -25 prestige and -200 relations penalty with the former vassal.

Designate as March

Main article: March

Designate a vassal as a March icon.png march, granting it substantial military bonuses but making it pay no taxes and preventing it from being annexed.

Rescind March

Revert a march to normal Vassal.png vassal status, allowing it to be annexed. Costs Icon stability.png -1 stability and gives a substantial relations penalty.

Annex vassal

The diplomat will begin peacefully annexing the vassal. This action can only be initiated during peace time, but war will not interrupt the progress once it has begun. (If annexation finishes while at war, be sure to find the armies and fleets formerly owned by the subject.) The requirements are

  1. Vassalage has lasted at least 10 years. The vassalization date can be found in the vassal's diplomacy screen on the tooltip for the vassalage icon Vassalage.png.
  2. Vassal opinion of overlord at least 190.
  3. Liberty desire is below 50%

Note: If during annexation the subject's liberty desire rises above 50%, annexation will pause and continue when liberty desire drops below 50% again.

The total cost of integration is 8 Diplomatic power.png per development of the vassal. This cost increased by any hostile core-creation cost modifiers any of the vassal's provinces may have, and decreased by administrative efficiency and modifiers that reduce annexation cost:

Diplomatic annexation cost Traditions Ideas Bonuses Policies
  • Influence idea 3: Integrated Elites
  • Influence-Administrative: Vassal Integration Act
  • Austrian idea 1: Imperial Ambition
  • British idea 1: The Acts of Union
  • Chagatai idea 3: Sons of Chagatai Khan
  • Cilli idea 1: Dynastic Marriages
  • Clevian idea 5: United Duchies
  • Gelre idea 7: Land Negotiations
  • Manx idea 7: The Act of Revestment
  • Zambezi idea 6: Wealth of the Shire Valley
  • Naxian ambition

. The full formula is

dip point cost = floor( sum[province]( 8 * (1 - administrative efficiency) * (1 + annexation cost modifiers) * (1 + local coring cost modifiers) * dev ) )

Note that there currently (1.13) is a bug that makes the tooltip in the diplomacy window display an incorrect cost prediction, as if rounding were applied for every point of development rather than after summing everything up. This may lead to significantly higher actual annexation costs than may usually be expected.

The overlord will invest diplomatic power into the integration process each month at the following rate:

  • Base: +1
  • Same religion: +1
  • Same culture group: +1
  • Diplomatic reputation: +1 per positive point, -1 per negative point

When the process ends, the overlord will gain +5 prestige, receive ownership of all the vassal's provinces, and gain cores on all provinces that the vassal had cores on at the time of completion. Local autonomy.png Local autonomy levels will be set to 60% for all integrated provinces unless the overlord already had a core on them.

Annexing a vassal will result in a 10 year penalty of -3 diplomatic reputation to the overlord. The penalty does not stack if multiple vassals are annexed. All other vassals of the overlord will have their opinion reduced by -30 as well, which will stack. If the annexed vassal was a member of the HRE, then the opinion penalty will also be extended to all members of the HRE. The annexation progress of foreign nations will appear in the diplomacy interface as a small vertical progress bar next to the shield icon of its overlord or vassal.


When target country is minor partner in a personal union, this will integrate it.


  1. Has been partner for at least 50 years.
  2. Relations of at least 190.
  3. Liberty desire is less than 50%

Note: If during annexation union partner liberty desire will rise over 50% annexation will pause and continue when liberty desire drops below.

The time to integrate a vassal or union partner depends on the vassal's total province development, the amount of diplomatic reputation overlord has, and other modifiers . The diplomatic annexation halts if the overlord does not have sufficient Diplomatic power.png diplomatic power. It costs 10 points/development to integrate lesser partner, modified by the following:

Diplomatic annexation cost Traditions Ideas Bonuses Policies
  • Influence idea 3: Integrated Elites
  • Influence-Administrative: Vassal Integration Act
  • Austrian idea 1: Imperial Ambition
  • British idea 1: The Acts of Union
  • Chagatai idea 3: Sons of Chagatai Khan
  • Cilli idea 1: Dynastic Marriages
  • Clevian idea 5: United Duchies
  • Gelre idea 7: Land Negotiations
  • Manx idea 7: The Act of Revestment
  • Zambezi idea 6: Wealth of the Shire Valley
  • Naxian ambition

Establish protectorate

Main article: Protectorate

The target country will become a protectorate. Protectorates are technologically inferior subject stations that retain more autonomy than vassals but do not occupy a relations slot; they grant much of their trade power to their overlord.


  1. The tech group difference between the player's country and the target country must be at least 50%.
  2. The target country is not at war.

Request protectorate

Ask the target country to become a protectorate or it.


  1. The tech group difference between the player's country and the target country must be at least 50%.
  2. Player is not at war.

Proclaim guarantee

Will call the player into the war if someone declares war on the guaranteed country. Uses a diplomatic relations slot and lasts until revoked or when a call to arms from the target is declined (which does not cause a loss of prestige). Can be revoked at will, which gives the former guarantor a truce on the formerly guaranteed country (but not vice versa). Only valid for countries that are significantly weaker.

Send warning

This will give the warner a defensive call to arms if the target country attacks one of the warner's neighbors. Rejecting this call to arms will incur all the same penalties as that for rejecting a normal defensive call to arms. The list of neighbors for any nation can be found in its diplomacy tab by filtering its relation list to neighbors only. A country cannot warn a country that has already warned it, or that is not significantly smaller. Warnings last for 20 years.

Threaten War

Threaten War is a new Diplomatic Action added in the Cossacks DLC. This diplomatic option lets a country demand a province that it has a claim or core on. If the demand is accepted, the province changes hands, otherwise war ensues as if declared using the Casus belli.png "Conquest" casus belli. War cannot be threatened over a country's Capital.png capital (therefore it is not possible to threaten war on a one province minor) or if a truce exists with that country. Threaten War will cause the threatening country to gain Aggressive expansion impact.png Aggressive Expansion and make the other nation lose Prestige.png Prestige, both based on the province Development.png development. Demanding a province will also create a 5 year truce. A country will give up their province if relative strength of the demanding country's alliance outweighs the relative worth of the province. The AI is more willing to give up provinces that the demanding country has a core on, and much less willing to give up provinces if that country has recently demanded another province.

Relations actions

See also: Relations

Improve relations

This sends a diplomats to the target country to improve relations over time. Relations can be improved up to +100 for independent realms, and up to +200 for subjects (vassals, lesser partners in personal unions). Improved relations decay by -3 on the first day of each year if there is no diplomat currently improving relations with the target country. The rate of relation improvement is highest when overall relations are near neutral.

When sending a diplomat to improve relations for the first time or when previous improvements already decayed (current improved relations value to that country opinion is 0 ) the player will gain double improved opinion on the first tick. The rest improvements will take place on the end of every month. In previous patches there was an exploit that helped to raise opinion quicker than normal by resending Improve Relations. This was fixed in 1.12.

Several ideas increase the rate relations can be increased. This bonus is called "Improve Relations", not to be confused with "Better relations over time", which makes bad relations decay more quickly.

Improve relations.png Traditions Ideas Bonuses Policies
  • Italian traditions (cU)
  • Yaroslavlyian idea 7: Russian Ambition
  • Iroquois ambition
  • Moldavian traditions
  • Holy Roman idea 3: Imperial Diplomacy
  • Antemoro traditions
  • Austrian traditions
  • Luban traditions
  • Humanist idea 6: Benevolence
  • Georgian idea 2: Georgian Isolation
  • Hadramhi idea 7: Distant Diplomacy
  • Liège idea 4: Wittelsbach Bishops
  • Montferrat idea 4: Savoyard Loyalty
  • Satake idea 7: Honorable Reputation
  • Saxe-Lauenburg idea 4: Claiming the Electorate
  • Takeda idea 4: Kurokawa Gold Mine
  • Veronese idea 5: Ending the Strife
  • Great Ming ambition
  • Kongo ambition
  • Mainzian ambition
  • Palatine ambition
  • Württemberger ambition
  • Wurzburgian ambition
  • Offaly traditions
  • Sardinian-Piedmontese traditions
  • Savoyard traditions
  • Swabian traditions
  • Diplomatic idea 4: Benign Diplomats
  • Jurchen idea 6: Generosity of the Warlord
  • Romanian ambition
  • Cham idea 5: Che Man's Legacy
  • Chiba idea 4: Sakura Kadan
  • Farsi idea 3: Diplomatic Prudence
  • Khivan idea 7: Great Power Diplomacy
  • Kildarean idea 2: Silver Tongues
  • Thüringian ambition
  • Humanist-Diplomatic: Multilingual Diplomats
  • Bremish idea 3: Deep Pockets
  • Frankfurter idea 4: Frankfurter Postzeitung
  • Khmer idea 2: Theravada Buddhism
  • Lan Xang idea 3: Court History Of Lan Xang
  • Sienese idea 6: The Saints of Siena
  • Silesian idea 1: Under the Influence
  • Imagawa idea 1: Claim to the Shogunate

Send an insult

This will give the target country a casus belli on the insulter for 1 year and lower relations by -50, decaying by +5 per year. Insults are useful for negating the -1 stability hit of declaring war on nations that have +100 relations with the aggressor. Insulting a rival will also grant +5 power projection, decaying by -1 per year, provided that the insulter neither has a truce with the nor already has power projection from a previous insult.

Dynastic actions

Royal marriage

For the dynastic effects of royal marriage, see Ruler#Royal marriage
For information on how to get more chance to obtain a personal union, see personal union

Countries ruled by monarchs may arrange royal marriages with others. This will improve relations by +25 while in effect. Attacking a country with an active royal marriage results in a -1 stability drop. The ties can be severed at the cost of -1 stability and -75 relations with the target country. The Papal controller can invoke divine dispensation and forgo the stability hit. Unlocking all Diplomatic ideas also removes the stability hit. The death of the ruler who proposed the marriage will end it without penalty.

On the death of a Christian monarch with no heir, a ruler from the dynasty of a more prestigious country with a royal marriage may come to the throne. If those countries already share a dynasty, a Personal union.png personal union may result instead. The higher a country's Prestige.png prestige when establishing a royal marriage, the higher its dynasty's chance of gaining the crown, independently or as a personal union.

Royal marriages are unavailable to republics (with the exception of Noble Republics and the Dutch Republic) and theocracies. Christians may only marry other Christians. All non-Christians may marry each other, but cannot get into personal unions.

The factors that influence an AI's decision to accept a royal marriage proposal are:

Factor Effect
Attitude towards proposer Friendly attitude Friendly: +40
Protective attitude Protective: +40
Threatened attitude Threatened: +10
Neutral attitude Neutral: -20
Hostile attitude Hostile: -100
Rivalry attitude Rivalry: -130
Nation opinion about proposer Positive: +0.25 per point
Negative: -0.25 per point
Same culture group +20
Same religion +5
Neighbors +5
Proposer's diplomatic reputation +5 per point
Distance between borders -0.1 per distance between borders

†: Distance between borders can only be seen in debug mode. It is possible to estimate distances using the fact that diplomats travel at a speed of 20 distance per day between capitals.

Break Royal Ties

This interaction breaks a Royal Marriage relation. This results in a -75 relations penalty with that country, a loss of -1 Prestige.png prestige, and a loss of -1 Icon stability.png stability. It does not affect relations with other countries. The stability loss is waived if the country target country is a rival, or the country breaking ties has completed the Diplomatic idea group or is Papal controller.

Attacking a country with whom the player has a Royal Marriage results in a -1 Icon stability.png stability hit, +1 Icon war exhaustion.png war exhaustion, and an additional penalty to their relations with that country.

Claim throne

For information on how to get a better chance of obtaining a personal union, see personal union

Claiming a throne is possible if one has royal marriage with the target country, shares a dynasty with the target, and the target has either no heir or a weak heir. Noble Republics, while able to marry, cannot claim or be claimed. The result of claiming the throne depends on whether or not the current ruler dies before producing an heir, and on the claimer's prestige. If either has rivals with higher prestige than the claimant, they get the option to start a succession war.

By claiming the throne of a country that has no heir and a king of a claimant's dynasty, the claimant will gain a casus belli to create a Personal union.png personal union, requiring 84% warscore regardless of the target's size. If the ruler dies on his own without an heir, the claimant will become the senior partner in a personal union, assuming no one with higher prestige has claimed the throne. However, a succession war can start if either country has a rival with higher prestige than the claimant, or another country has also claimed the throne. A succession war can start even while the claimant is at war.

Note that, unless the player shares a dynasty and intends to go to war, this makes claiming the throne on a ruler who already has a weak heir a bad idea, as both the heir and the ruler will need to die for the player to get anything.

Regardless of the result, claiming the throne of a country will reduce relations by -50 with other countries the claimant has a royal marriage with and by -100 with the target country, and incur a loss of Prestige.png -20 prestige. The casus belli lasts until the target country produces an heir with a strong claim.

Only Christians can claim the thrones of other nations (since non-Christian nations almost never entered personal unions historically).

Support heir

Supporting an heir is an action that replaces 'claim throne' in the diplomacy screen for nations that have a elective monarchy (which can only be gained by event for Flag of Poland Poland and the Flag of Commonwealth Commonwealth, or by using a custom nation). Any nation that has a royal marriage with the elective monarchy may support heir.

In an elective monarchy, each nation that the elective monarchy has a royal marriage with (and also the elective monarchy itself) has an heir to the throne. Each heir also has a certain amount of support. A nation may thus send a diplomat to support their own heir in the elective monarchy, which has a certain chance of increasing the heir's support every month (the exact probability is dependent on the nation's relations with the elective monarchy and the nation's [diplomatic reputation]). The elective monarchy may also choose to support its own heir by 5 points by taking a loss of Legitimacy.png -10 legitimacy. After the death of the elective monarchy's current monarch, the heir with the most support becomes monarch and the nation that controls the heir gains a legitimacy and prestige boost, some monarch points and a relations boost with the elective monarchy.

Covert actions

See also: Espionage

Fabricate claims

A diplomat can be sent to fabricate a claim on a neighboring province, or a province that shares a sea zone with an owned province. Once a claim is established, the claimant now has a legal reason to start a war and gains the conquest casus belli. Claimed provinces allow a nation to select them as a wargoal when declaring war. Provinces with a claim cost less warscore in peace deals and have -10% coring cost, as well as only having 40% autonomy, instead of the usual 50% for unclaimed conquered provinces.

A fabricated claim lasts for 25 years, and will only be removed if its time runs out or the province is cored by the claimant. Claims cannot expire naturally if the claimant and the owner of the province are at war or have a truce, and their duration will automatically be extended to account for this. Despite the listed expiration dates on claims, the game only checks for their removal on the first day of each month. This gives the claimant a small window of opportunity to declare war again if the claim was extended by a truce: while truces are normally removed on the first day of each month as well, one can force them to expire on time by saving and reloading the game. See truce for more details.

Claims that are granted by missions behave just like fabricated claims, although their duration may be different depending on mission parameters.

Fabricating a claim takes 1 year, modified by the following:

Cost to fabricate claims.png Traditions Ideas Bonuses Policies
The modifier “time to fabricate claims” was renamed with patch 1.16.

Being at war with the target nation will increase the fabrication time by +50%. If the war concludes while the fabrication is still in progress, the fabrication time will return to normal, and may result in it being completed immediately. It is not clear how this war penalty stacks with bonuses to fabrication time yet. The fabrication progress will also be paused if the targeted province comes under siege by a force other than the fabricator, but it will resume once the siege is resolved.

Justify trade conflict

This action sends a diplomat to fabricate a trade conflict casus belli at the target country. The target must have at least 20% of the trade power in a trade node in which the fabricating country has at least 10% trade power and a Merchants.png merchant present. Once a trade conflict casus belli is established, the fabricating country now has a legal reason to start a war. Trade conflict casus belli last 2 years. If the diplomat is discovered during the fabrication process, it will result in a -7.5 Aggressive expansion impact.png aggressive expansion penalty.

The time required to justify a trade conflict is 270 days—slightly short of 9 months—and is affected by the following modifiers:

Justify trade conflict cost.png Traditions Ideas Bonuses Policies
The modifier “time to justify trade conflict” was renamed with patch 1.16.

Justifying a trade conflict is often the best way to get a casus belli on a distant nation whose provinces cannot be claimed.

Support rebels

Main article: Rebellion#Support rebels

Send a diplomat to a nation to support the local rebels. This will increase the unrest of that rebel faction in the target country. The player may choose to support any rebel faction that has a greater than zero National unrest.png unrest anywhere within the target nation.

Supported rebels will be treated as allied units, regardless of when the support them began. If the rebel faction has spawned rebel units in multiple countries, then all those units will be treated as allies once support is given to that faction anywhere.

Allied rebels that are sieging a province that is an objective of theirs will not transfer leadership of the siege to the player in a war. If allied rebels cannot complete their objectives because the province they are trying to occupy is under another nation's control, they will instead wander the countryside and may engage enemy units.

Rebel support efficiency.png Traditions Ideas Bonuses Policies
  • Full Espionage
  • Espionage-Economic: The Foreign Support Act
  • Samtskhe traditions
  • Piratical idea 7: Life of Liberty
  • Humanist-Espionage: Cultural Understanding
  • Leinster idea 3: The Subject of My Enemy is My Friend
  • Palatinate idea 3: Center of Reformation in Southern Germany

May infiltrate administration.png Infiltrate administration

If a nation wants to infiltrate the administration of another country they will need to have the Espionage spy idea to take this covert action. So long as a diplomat is present in the enemy capital, the fog of war is lifted over their country, revealing everything within their territory. As soon as the diplomat is discovered, he is sent home and the fog is returned.

May sow discontent.png Sow discontent

If a nation wants to sow discontent in another country they will need to have the 'Destabilizing Efforts' spy idea to take this covert action. So long as a diplomat is present in the enemy capital, the target country gets more expensive stability costs, and a higher chance of revolt. A country can only be targeted by either one sow discontent at once.

May sabotage reputation.png Sabotage reputation

If a nation wants to sabotage the reputation of another country they will need to have the 'Rumourmongering' idea, the third available in the Espionage idea group. So long as a diplomat is present in the enemy country, all neighbours, enemies and rivals of the targeted country gets an opinion penalty towards the target. This will make it more difficult for the target to recover its reputation from recent expansions or betrayals, to make alliances and to enter other diplomatic agreements. A country can only have one sabotage on them at the same time.

Study technology

Gives +1 monarch point per level behind in technology, up to +2 per category.

Agitate for Liberty

Give a subject nation bonus liberty desire, up to +25%.

Economy actions

See also: Economy

Transfer trade power

Ask a target non-subject nation to transfer a percentage of its trade power to the player. While a transfer of trade power is active, the two nations involved cannot declare war on each other, and will also receive a mutual relation bonus of +20 per 100% of power transferred. The agreement counts towards each country's diplomatic relations limit.

The factors that influence an AI nation's desire to accept a request to transfer trade power are

Factor Effect
Proposer military power compared to nation +80 max
Proposer base tax compared to nation +20 max
Attitude towards proposer Threatened attitude Threatened: +20
Friendly attitude Friendly: +10
Hostile attitude Hostile: -100
Proposer is not allied with or guaranteeing nation -50
Nation opinion of proposer +0.1 per positive relation
Diplomatic reputation.png Diplomatic reputation Positive: +1 per point
Negative: -2.5 per point
Trust +0.2 per positive point
Amount of power asked for Starts at +20 with 10% power. For each percentage increment between
10–40%: -1
41-60%: -3
61-80%: -5
81-100%: -7
Number of countries transferring trade power to proposer -10 per transfer trade power agreement
Distance between borders

Issue embargo

Reduces the Trade power.png trade power of the target country in any trade node the embargoing country has trade power in, depending on several factors. Embargoing a rival grants power projection. Embargoing a non-rival gives a penalty to trade efficiency, but can give a net gain in trade power share (and hence income) if the other country is very dominant in an important node.

The following bonuses apply to embargo efficiency:

Embargo efficiency.png Traditions Ideas Bonuses Policies
  • Espionage idea 6: Privateers
  • Vermont idea 2: The Boston Tea Party
  • Betsimisaraka idea 2: Pirate Ports
  • Cebu idea 5: 'The Place for Trading'
  • Cypriot idea 7: Raid Turkish Commerce
  • Malagasy idea 3: Pirate Ports
  • Mindanao idea 7: Pirates of Mindanao
  • Montenegrin idea 4: Balkan Gusars
  • Naxian idea 3: Archipelago Of Opportunities
  • Pomeranian idea 1: Legacy of Pirates

Send gift

Allows the player to send money to improve relations with a country, up to a maximum of +25. The gift amount can be adjusted in increments of Gold Icon.png 25 ducats. The effect of the gift is

relation bonus = 2.4 * ducats gifted / monthly income of target country

The final value is rounded down to the nearest integer. The relation bonus will last for 5 years. Additional gifts sent during this time will have no effect unless they

Loan offer

Allows the player to loan out money to other countries for interest. When the loan is due to be repaid, the loan-taker can instead choose to keep the ducats. This will give the loan-giver a casus belli. This is disabled for any AI countries, as it was basically a "free CB" button, due to the AI's misuse of loans.

Give subsidies

Transfer a specified amount of money each month to the target country for a certain duration. The sender may transfer between Gold Icon.png 0.1 ducats and +50% of its monthly income to the target country each month, adjustable in increments of 1% of its monthly income. The duration of the subsidy can be set between 10 and 400 years, adjustable in increments of 10 years.

Maintaining subsidies will improve the target country's relations with the subsidiser each month, up to a maximum of +15. The accumulated relation bonus is completely removed when the subsidy is cancelled or expires. Since there is otherwise no penalty for terminating a subsidy early, it is generally good practice to set a long subsidy duration unless diplomat time is severely constrained. The relation bonus is

yearly relations increase = 12 * monthly subsidy / target country's total monthly income

All monthly income mentioned in this section refers to the monthly income as reported in the ledger. Be aware that the target country's total monthly income will therefore include this monthly subsidy once the ledger is updated after the establishment of the subsidy. This imposes significant diminishing returns on the relation benefits of a large subsidy, and encourages one to maintain smaller subsidies over a longer time frame instead.

Example: Country A has a monthly income of 10 ducats, and country B provides it with a monthly subsidy of 5 ducats. The reported yearly relations boost will start at +6 per year (B's subsidy is 1/2 of A's income), then immediately drop to +4 per year after the first month (the subsidy is now 1/3 their income).

Subsidies do not consume a diplomatic relations slot. This makes them a valuable tool for blandishing future targets of diplomatic vassalization or annexation.

Subsidizing a nation at war with a rival grants Power projection.png power projection.

Sell province

A province can be sold to an another nation for a price of 0 to 2,000 ducats at a cost of Prestige.png -10 prestige. Both the buyer and seller must be at peace, and neither can be rivals of the other party. Only one province can change hands in a single transaction. The AI will sometimes offer to sell isolated provinces to the player, particularly if it is unable to core them.

When attempting to sell a province to an AI nation, it will consider a list of positive and negative reasons listed below, in order of precedence:

A province can always be bought as long as the price is affordable if:

  • Buyer is a subject and seller has a core on the province
  • Buyer has core on province

A provinces will never be bought due to a -1000 modifier if:

  • Province is priced above current treasury of buyer
  • Buyer has no core or claim on province that is of a different culture group
  • Buyer has no core or claim on province that is of a different religious group
  • Buyer has no core on province and is currently overextended by any amount
  • Buyer has no core on province that is part of the Holy Roman Empire
  • Buyer cannot core province due to limited colonial range, or because the province is landlocked and not adjacent to buyer

Additionally, it is not possible to sell a province to a colonial subject if the province is not in its colonial region.

Other minor modifiers that merely affect the price of the province are:

  • Provinces are valued at 100 ducats per base tax in most instances where a sale is possible
    • Adjusting the sale price from this baseline value will give a +0.1/-0.1 modifier per ducat per base tax.
    • Selling a province for 0 ducats will therefore give a +10 modifier per base tax.
    • If the province is particularly undesirable to the buyer, then its base value and associated price modifier will both be halved.
  • A -1 modifier is applied for every 1% that the sell price exceeds 50% of the treasury of the buyer.
  • Province is adjacent to buyer grants +10.
  • Province has the same culture as buyer grants +10.
  • Province has the same religion as buyer grants +10.

Selling provinces to a vassal is one method of vassal feeding. It is useful for avoiding overextension in the short term, and exchanges immediate Administrative power.png administrative coring costs for Diplomatic power.png diplomatic annexation costs later. The Cossacks DLC enables giving provinces to vassals directly via the subject interactions interface, making selling provinces to them unnecessary.

As AI nations place a very high priority on core creation, one can delay their research progress in administrative technologies by selling them provinces with a high Administrative power.png coring cost. This can be particularly useful if the next administrative technology would otherwise unlock a troublesome idea group (e.g. AI Portugal's first idea group is always exploration).

Access actions

Ask for military access

Request military access from the target country, allowing the requester's land armies to pass through its territories. Acceptance will raise the requester's opinion of the host country by +10, while rejection will decrease it by -10. Declaring war on a country that is granting the aggressor military access causes a major -5 hit to stability.

AI nations will only grant military access if they have more positive than negative reasons for doing so. The relevant factors are

Factor Effect
At war with neighboring rival +150
Has alliance +50
Requester army strength +100 max
Attitude towards requester Friendly attitude Friendly: +20
Defensive attitude Defensive: +20
Protective attitude Protective: +20
Threatened attitude Threatened: +20
Neutral attitude Neutral: 0
Unknown attitude Unknown: 0
Hostile attitude Hostile: -100
Rivalry attitude Rivalry: -100
Requester diplomatic reputation Positive: +3 per point
Negative: -3 per point
Nation opinion about requester Positive: +0.2 per point
Negative: -0.5 per point
Trust 0.5 per point

Military access is shared for all participants in a war. For example, if France and Brittany are in a war against Burgundy and France requests military access from Savoy, then Brittany will also have military access to Savoy. Similarly Burgundy, and all of its war allies, would also gain military access to Savoy.

Subject nations always give military access to their overlord. All participants in a war automatically grant military access to their allies, as well as being able to march into their enemies' territory. An army in non-allied land when war is declared, or in territory without military access when war ends, will be exiled.

Offer military access

Offer military access to the target country, allowing their land armies to pass through the requester's territory. Acceptance will raise the target country's opinion of the requester by +10. AI nations are typically uninterested in obtaining military access unless they are the country's ally or subject, or the country is a large and sprawling. Countries automatically gain military access to countries that grant military access to someone they are at war or allied with.

A country can't revoke access to someone if they, or someone they are at war with, still has troops inside the country's borders.

Fleet basing rights

Acquiring fleet basing rights from a nation will give the following benefits:

  • Naval supply range will now extend from the ports of that nation.
  • Trading range will now extend from the ports of that nation.
  • The requester may dock and repair ships in the ports of that nation.
  • The requester may disembark ground troops in that nation by docking loaded transports at its ports. These land troops will not be exiled, and may move into any adjacent province that they would normally be able to enter.

The cost of purchasing fleeting basing rights is as follows:

  • The base cost is Gold Icon.png 0.1 ducats per month per port, with a minimum of Gold Icon.png 0.5 ducats and maximum of 2.0 ducats. This fee is based on the count of permanent ports.
  • Non-city colony ports are usable and count toward the fee.
  • Ports that reside in a province which are terra incognita to the receiving country also count toward the fee.
  • Occupied ports only charge a fee if they can be docked at.
  • The fee can be seen in the economy window under Harbor Fees.

Fleet basing rights no longer extend colonial range as in past versions of the game. They can still be used to great advantage by distant fleets however. With El Dorado.png El Dorado active, they are no longer useful to explorers since they no longer take attrition while exploring. Only nations that have diplomatic technology level 2 or higher can grant fleet basing rights.

The following factors will influence an AI nation's decision to grant fleet basing rights:

Factor Effect
Nation is allied to requester +50
Nation opinion of requester Positive: +0.2 per point
Negative: -0.5 per point
Attitude towards requester Friendly attitude Friendly: +20
Defensive attitude Defensive: +20
Protective attitude Protective: +20
Unknown attitude Unknown: 0
Neutral attitude Neutral: -20
Threatened attitude Threatened: -30
Hostile attitude Hostile: -100
Outraged attitude Outraged: -150
Rivalry attitude Rivalry: -150
Trust +0.5 per positive point
Requester diplomatic reputation Positive: +3 per point
Negative: -3 per point
Requester is embargoing nation -1000
Asked nation is embargoing requester -1000

Once fleet basing rights have been obtained, AI nations will generally not revoke them unless there is a drastic change in relationship.

Papal actions

These actions are available to the Curia controller.

Call for crusade

Main article: Curia#Call_a_crusade

The Curia controller can call a crusade against a single target.


Main article: Curia#Excommunicate

The Curia controller can excommunicate any Catholic nation that the Papal States holds a negative opinion of. This action can only be performed once every 3 years.

Emperor actions

These actions are available to the Emperor of the Holy Roman Empire.

Grant electorate

Grant the electorate to an independent nation within the Empire. This action is possible when the Empire has fewer than 7 Electors.

Demand unlawful territory

Main article: Holy_roman_empire#Unlawful_Imperial_territory

Unlawful Imperial territory is a province that is in the HRE, but is owned by a country that does not have a core on it (even if the owning country is in an HRE member). If the target country accepts the request, the province will return to a rightful owner. If the target country refuses, the emperor will receive a casus belli against the target country and its relationship with him will decrease by -25.

Bestow imperial grace

This action gives the Emperor a +40 relationship modifier with another nation within the Empire at the expense of Imperial authority.png -1 Imperial Authority. This relationship bonus will disappear if the country stops being emperor.

Demand religious conversion

Demand that the nation adopt the Emperor's religion; refusal gives a casus belli. Gives a relations penalty with all other member states of the target's current religion. Electors will never agree to change religion. This is only possible if the Empire has an official religion.

Remove electorate

Remove an elector at the expense of worsened relations with other electors and Imperial authority.png -10 Imperial Authority. This action is not available unless the HRE has an official religion.

Grant Free City status

Grant Free City status to nations in the HRE that only own one province. Free Cities get a special republican government, a bonus to Tax income.png tax income and will always be able to call in the Emperor when they are attacked, even in internal HRE wars. The Emperor gets a bonus to Tax income.png tax income, Manpower.png manpower and Imperial authority.png imperial authority for each Free City in the HRE, but there can only be 8 Free Cities in total at any given time. A Free City that gains a second province or leaves the HRE will lose their Free City status. Free Cities cannot be Electors. Monarchies get a -50 penalty to accepting and theocracies get -100, so getting one-province republics released may be necessary to create more free cities.


These actions are not in the main list, but are also conducted via the Diplomacy panel.

Select rival

The Rival Mechanic added in Wealth of Nations DLC

Up to three countries may be selected as rivals at any time. Rivals may be only selected from countries that are comparable in power; if a rival becomes too weak or too strong it will cease being a valid rival. Nations must be relatively near to be eligible rivals, with more powerful countries able to have rivals at greater distance. In order to be rivals both countries must have each other discovered. Selecting a rival has the following effects:

  • The country is an enemy of their rivals, with its attendant effects on diplomacy.
  • +25% Prestige.png prestige from defeating a rival in battle.
  • No Trade efficiency.png trade efficiency penalty from embargoing the rival.
  • +20% Spy network construction.png spy offense against the rival.
  • -33% Diplomatic power.png Diplomatic Power cost for demanding unjustified provinces from the rival in peace deals.

Having a rival and taking actions against it grants Power projection. Not having enough rivals gives a penalty to Power projection

Create vassal

This releases a country as a Vassal.png vassal. The released country gets all of their core provinces that are owned by the releasing country, except for the releasing country's capital if applicable. Nations can only be released if at least one owned province is both a core of the nation and has its primary culture.


  1. See in /Europa Universalis IV/common/static_modifiers/00_static_modifiers.txt (Static modifiers#Base values).