Diplomacy

The diplomacy interface, as the player nation, viewing France

Diplomacy in EU4 is the system that involves all relations and actions with other nations. Relations can be increased through alliances, coalitions, common wars, common rivalries, decisions, events and having a diplomat improve relations. Relations are decreased by declaring war, being rivals, sending insults, having a different religion, breaking/dishonoring an alliance, events and decisions. Diplomacy is a bilateral system and will affect relations on both sides of an agreement.

Reasons for a nation's opinion of 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. Three additional categories are available to any nation that qualifies for them:

• The emperor of the Holy Roman Empire has an extra category: Emperor actions.
• The Papal controller also has an extra category: Papal actions.
• The leading 8 powers of the world have an extra category: Great Power actions.

The declare war and sue for peace diplomatic options are found outside of these categories.

Diplomats

A diplomat is required to perform most diplomatic actions. Some actions - improving relations, annexing a vassal, building up a spy network and counterespionage - will occupy a diplomat indefinitely or until completion of the task, unless the diplomat is manually recalled. Actions that will occupy a diplomat for a period of time will display a diplomat icon () on their button. Other actions are immediate.

When initiating a mission, a diplomat takes one day to reach the target country and begin its mission. After completing a mission, a diplomat will be unavailable while he travels back home, the time which scales based 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 has 2 diplomats by default. Additional diplomats may be gained through the following triggers, ideas and policies:

	Triggers
+1	As Kingdom or Empire As Curia Controller As Holy Roman Emperor after ‘Institute Reichsregiment’ reform As Emperor of China after ‘Reform Seaban’ reform As Shogunate With parliament and ‘Expand the Diplomatic Corps’ as active issue for 10 years. As Tengri country and Theravada as secondary religion As AI-controlled country (reserved for short-term actions)

	Traditions	Ideas	Bonuses	Policies
+1	Aachen traditions Ajami traditions Hausan traditions Kurdish traditions Mori traditions Samtskhe traditions Sligonian traditions Thüringian 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 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 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

Diplomatic relations cap

The number of other countries a nation can have diplomatic agreements with is limited. Each relation over the cap costs 1 diplomatic monarch point per month. The limit only counts for the number of different countries with whom an agreement has been closed, not the number of agreements. Having multiple agreements with a single nation only counts as one diplomatic relation.

Agreements that count towards the cap include:

• Alliances
• Royal marriages
• Guarantees
• Having a vassal or junior personal union partner
• Receiving military access
• Supporting independence
• Having a client state

Agreements that do not count toward the cap include:

• Granting military access
• Receiving or granting fleet basing rights
• Receiving or granting loans
• Coalitions
• Federations
• Embargoes
• Warning other nations
• Giving subsidies
• Having a colonial subject or protectorate
• War reparations
• Transferring trade power (including enforced 'transfer trade' as part of a peace agreement)
• Having vassals who are members of the empire as the Holy Roman Emperor, if Revoke the Privilegia has been passed.
• Receiving conditional military access (e.g. within the HRE due to being in a war with the Emperor, or with someone else who has access)

Increasing the diplomatic relations cap

The base diplomatic relations cap is 4 diplomatic relations. It is affected by the following:

	Conditions
+1	Holy Roman Emperor Nahuatl after Extend Pochteca Obligations reform Player bonuses AI (reserved for diplomacy with the player)
−1	Temples faction for Celestial empire Native council government Tribal government Kingdom
-2	Tribal government Duchy

Ideas and policies:

	Traditions	Ideas	Bonuses	Policies
+2	—	Provençal idea 5: Public Weal	—	—
+1	Antemoro traditions Burgundian traditions Isshiki traditions Jaunpuri traditions Ladakh 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 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 Greek idea 6: Philhellenism Hausan idea 1: Heirs of Bayajida 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 Manipur idea 6: Bengali Influence Mazovian idea 3: Between Monk, Eagle and Purse Mori idea 3: Diplomatic Intrigues Orleanaise idea 6: French Language in All Courts Polotskian idea 6: Diplomatic Initiative Québécois idea 3: Relations with the First Nations People Satake idea 5: Eastern Coalitions Saxon idea 5: Corpus Evangelicorum Swahili idea 7: Familiar Presence Abroad 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 Yamana idea 3: Mediate Succession Disputes	Aachen ambition Ajami 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 may also give a temporary increase in the relations cap.

Diplomatic reputation

A nation's diplomatic reputation represents its overall diplomatic ability and credibility. Diplomatic reputation is visible in the diplomacy window of the country screen.

Effects

Diplomatic reputation positively affects both subject relations and relations with sovereign nations.

With subject nations, each point of diplomatic reputation gives:

• +5% chance to inherit lesser partner in a personal union
• +1 diplomatic power used per month while annexing vassals or union partners
• -3% to the liberty desire of all subject nations

With other countries, each point of diplomatic reputation gives the following bonuses when 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
Request to share maps	5
Demand unlawful territory	3
Grant free city status	3

Gaining diplomatic reputation

Diplomatic reputation can be increased by completing certain missions, as well as by the following modifiers and ideas:

Modifiers

• Legitimacy: -1 at 0 legitimacy to +1 at 100 legitimacy
• Overextension: -2 per 100%
• Trading in Ivory: +2
• Statesman advisor: +1
• Subjugation of the Papacy (Triggered Modifer for Catholic Nations): -2
• The Occupation of Rome: -1
• Being a member state of the HRE: +1 for non emperor HRE members
• Institute Reichsregiment (HRE reform): +1 for the Emperor
• Enact Gemeiner Pfennig (HRE reform): +1 for non emperor HRE member
• Hindu state with Ganesha as patron deity: +1
• Buddhist state with balanced karma: +1
• Catholic state with Papal Influence spent on the "Send papal legate" option: +1 for 20 years
• Reformed state with stability focus: +1
• Tengri state with Catholic syncretic faith: +1
• Fetishist state: +1
• Austrian Diplomacy (available only to Austria) during Age of Revolutions (requires Mandate of Heaven DLC):+5
• Annexed Vassals: -3 for 10 years
• Dishonored alliance: -1 for 5 years
• 'Foreign Contacts' modifier triggered by Diplomatic missions: +1 for 10 years
• 'Offices of Maritime Trade' faction of the Celestial Empire government: +1
• 'The Jacobins' faction of the Revolutionary Republic government: -2
• 'The Imperials' faction of the Revolutionary Republic government: +1
• Native council Native diplomatic idea 2: Smoke Ceremonies: +1
• Diplomatic idea 'Improved Reputation' modifier: +1 for 10 years
• Diplomatic idea 'Babbling buffoons' modifier: -1 for 10 years
• Expansion idea 'Enhanced Reputation' modifier: +1 for 10 years
• Expansion idea 'Diplomatic Faux Pas' modifier: -1 for 10 years
• Influence idea 'Popular Noble' modifier: +1 for 10 years
• Reichshofrat - an event for Austria: +1 for the rest of the campaign
• Internal Conflicts National Instability: -5 for 10 years
• Diplomat advisor Excellent Diplomacy: +1 for 10 years

National ideas and traditions, idea groups and policies

	Traditions	Ideas	Bonuses	Policies
+2	—	Diplomatic idea 5: Experienced Diplomats Influence idea 5: Diplomatic Influence Aachen idea 7: Congresses of Aachen Austrian idea 4: Habsburg Dominance Roman idea 2: Legacy of Rome Jerusalem idea 7: Cosmopolitan Nobility	—	—
+1	Date traditions Delhian traditions French traditions Hessian traditions Iroquois traditions Novgorodian traditions Odoyev traditions Papal traditions Provençal traditions Ryukyuan traditions Silesian traditions Sukhothai traditions Yamana traditions	Afghan idea 4: Afghan Diaspora Ajami idea 4: Persian Language and Court Culture Ansbach idea 3: Plassenburg 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 Betsimisaraka idea 7: European Diplomacy Bremish idea 1: Lex Saxonum Breton idea 6: League of the Public Weal 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 Ethiopian idea 4: Diplomatic Demeanor 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 Hanoverian idea 6: Hanoverian Chancery 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 Manipur idea 7: Far-Reaching Diplomacy Mapuche idea 6: Peace Parliaments Maravi idea 2: Mlira Cult Meath idea 2: Foreign Nationals Mesoamerican idea 3: The Ball Game 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 Tibetan idea 5: Potala Palace Trebizondian idea 4: Komnenoi Princesses Ulster idea 3: Civilist of the Irishry Vindhyan idea 1: Rajput Connections Wallachian idea 1: Cunning Diplomacy Wurzburgian idea 2: Duke in Franconia Yarkandi idea 3: Tarikh-i-Rashidi Yaroslavlyian idea 2: Third Option	Assamese ambition Medri Bahri 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

Diplomatic actions

War

Main article: Warfare

Declaring war initiates a military conquest against the target country. A casus belli can be selected and the allies of both sides are shown in the declare war screen. Winning battles, achieving the wargoal, and occupying provinces accumulates war score for both parties, by which peace terms may be agreed upon. At war a country can offer a peace deal (sue for peace) or an unconditional surrender.

Alliance actions

Form coalition against

Main article: Alliance#Coalition

A coalition is an alliance of nations who have bonded together against a common enemy because of this enemies' very high aggressive expansion. Coalitions members will automatically be offensively and defensively called to arms in any direct war between a coalition member and the coalition target.

Offer alliance

Main article: Alliance

An alliance is a military agreement of mutual support in wars between two nations. The strength of an alliance is based on trust and favors with the alliance partner.

Support independence

Nations may support the independence of a nation if the target nation is a subject nation and has a liberty desire of over 50%. If the target nation declares a war of independence, all nations supporting its independence will automatically ally the target nation and join the war against the former overlord of the now (temporarily) independent nation.

Offer condottieri

Main article: Condottieri

A nation may rent out their armies to another nation in exchange for payment, while maintaining manual control of the army. A maximum of 20 regiments can be rented out simultaneously.

Trade league

Main article: Trade league

Trade leagues are a group of small countries banded together to boost trade and provide defensive protection to each other. Only single province countries can join a trade league. A trade league must be lead by a Merchant republic or Veche republic.

Influence actions

Enforce peace

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

• The enforcer must not have a truce with the leading attacker.
• The enforcer 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 without triggering any automatic defensive call to arms from the opponent. For example, European powers outside the Holy Roman Empire can use enforce peace on empire members to enter wars against them without having to fight the Emperor. Enforce peace can also turn the tides against a rival's offensive war.

Offer vassalization

Main article: Vassal#Offer vassalization (diplomatic)

Vassalization makes the target nation a subject nation of the country that offered it. Vassals are automatically called to their overlord's wars and pay a portion of their tax income.

Break vassalization

Breaking vassalization cancels a subject nation's vassalage and makes them independent. This action costs -25 prestige and -200 relations penalty with the former vassal, and results in a truce of 5 years with the former overlord. Vassalization cannot be cancelled when a truce exists with the target.

Designate march

Main article: March

Designating a vassal as a march grants it substantial military bonuses. Marches do not pay tax income to their overlord, and cannot be diplomatically annexed or peacefully released.

Revoke march

Main article: March

Revoking a march changes it to normal vassal status, allowing for it to be annexed. This action costs -1 stability and results in a -50 relations penalty with the subject.

Annex vassal

Main article: Vassal#Annexation

Diplomatic annexation incorporates a client state or vassal into the overlord's domain, resulting in direct control of the former subject's territory and military. This action occupies a diplomat for its duration and costs diplomatic power.

Integrate

Main article: Personal Union#Integration

Diplomatic integration incorporates a junior parter of a personal union into the senior partner's realm. Like diplomatic annexation of vassals and client states, completion results in control of the junior partner's territory and military, but also gains control of the junior partner's vassals and colonial nations. Diplomatic integration of a junior partner in a personal union follows nearly the same principles for requirements, cost, speed, and effects as diplomatic annexation of a vassal.

Proclaim guarantee

Guaranteeing a nation calls the guarantor to war if the target nation is directly attacked by another nation. The guarantor will not be called to war if the guaranteed nation is called into another war as an ally, unless they are called in as a co-belligerent. The relation uses a diplomatic relations slot and lasts until revoked or a call to arms from the target is declined. A call to arms from a guarantee functions identically to a defensive call to arms in an alliance and carries the same penalties if declined. Guarantees can be revoked at will, which gives the former guarantor a truce on the formerly guaranteed country (but not vice versa). It is only possible to guarantee countries that are significantly weaker than the guarantor - protection from a weaker nation will not be taken seriously.

Send warning

Sending a warning to a target country results in a defensive call to arms if the target attacks one of the warner's neighbors. Rejecting this call to arms only incurs a penalty to trust with relevant nations. 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 another country it is already warned by, or that is not significantly weaker. A warning lasts for 20 years and can be issued again once it expires.

Threaten war

Threaten war is a diplomatic action which lets a nation demand a province that it has a claim or core on. If the demand is accepted, the province is transferred to the demanding nation. If the demand is not accepted a war is declared with the Conquest casus belli for said province. War cannot be threatened over a country's capital (it cannot be targeted at an OPM) or if a truce exists with the target country, and nor can a subject nation (other than Tributaries) threaten war. Successfully demanding a province will cause the threatening country to gain aggressive expansion as if the province had be conquered in a peace deal and the target nation to lose -10 prestige. This also creates a 5-year truce between the two nations. A country will relinquish a province if the relative strength of the demanding country's alliance outweighs the relative worth of the province and the alliances of the threatened nation. 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.

Factors that influence the AI's willingness to giving up a province are:

Factor	Effect
Base value:	-20
Province is not a core of the threatening nation:	-20
Relative strength of alliances:	-100 to +100
Relative worth of province to target's entire development:	-1 to -200
Recently gave in to threat:	Base of -120, increasing by +1 per month after truce ended

Relations actions

See also: Relations

Improve relations

Improving relations sends a diplomat to the target country to improve relations over time. Relations can be improved up to +200 for subjects and up to +100 for all other nations. 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 at which relations improve is highest when relations are 0, and decreases as the difference increases. This rate can be further improved by the improve relations modifier. Any bonus to the improve relations modifier also affects how fast any accumulated aggressive expansion will decay.

When sending a diplomat to improve relations for the first time or when the improved relations value has decayed to 0 doubly improved opinion is gained on the first tick. The rest of the relations improvements take place at the end of each month.

Send an insult

Sending an insult gives the target country the ‘Diplomatic Insult’ casus belli on the insulter for 1 year. The target country also gets the opinion modifier “Insulted” towards the insulter for 10 years, worth −50 opinion with a yearly decay of +5. Insults are useful for negating the −1 stability hit of declaring war on nations that have +100 relations of the aggressor. Insulting a rival also grants +5 power projection, decaying by −1 per year, provided that the insulter neither has a truce with them nor already has power projection from a previous insult.

Scornful insult

A scornful insult will double the loss of opinion – the opinion modifier “Insulted” is replaced by the opinion modifier “Scornfully Insulted”, worth −100 opinion – at costs of 5 prestige (only possible with a positive prestige). Scornfully insulting a rival gains +10 power projection. Rivals of the target country get the opinion modifier “Scornfully Insulted Enemy” towards the insulter for 10 years, worth +25 opinion with a yearly decay of −2.5.

Dynastic actions

Royal marriage

For the dynastic effects of royal marriage, see Ruler#Royal marriage

For information on personal unions, see personal union

Countries ruled by monarchs may arrange royal marriages with others. This improves relations by +25 while in effect. Attacking a country with whom a nation has a royal marriage results in -1 stability and +1 war exhaustion. Note that this penalty will not occur except through a standard declaration of war; to circumvent it, the player may find it useful to Threaten War over a province that the target will refuse to cede.

Upon the death of a Christian monarch with no heir, a ruler from the dynasty of a more prestigious country that shares a royal marriage may rise to the throne. If the countries already share a dynasty, a personal union may result instead. Personal union partners function militarily like vassals. They do not pay a portion of their tax income but may be inherited. Higher prestige increases chances of gaining the crown of a royal marriage partner for a country's dynasty, either independently or as a personal union.

Royal marriages are unavailable to theocracies and republics, with the exception of the Dutch Republic. Christians may only marry other Christians. All non-Christians may marry each other, but personal unions will only occur for Christian nations.

The factors that influence a nation's acceptance of a royal marriage proposal are:

Factor	Effect
Attitude towards proposer	Friendly: +40
	Protective: +40
	Threatened: +10
	Neutral: -20
	Domineering: -980
	Hostile: -1000
	Outraged: -1000
	Rivalry: -1000
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.

Break royal ties

Breaking royal ties ends a royal marriage. This results in -1 stability and -1 prestige. Furthermore, the relation with the target country is decreased by -75. The stability cost may be negated by completing Diplomatic ideas or being the Curia Controller. The death of the ruler who proposed the marriage will also end a royal marriage without penalty. Breaking royal marriages with rivals also does not incur a stability cost.

Claim throne

For information on improving chances of obtaining a personal union, see Personal Union

Claiming a throne gives the "claim on throne" CB, a military means of forcing a personal union.

The requirements to claim a throne are as follows:

• Target has a royal marriage
• Target shares the same dynasty as claimant
• Target has a weak claim heir or no heir
• Claimant has more prestige than target

Claiming the throne of a country results in the following diplomatic effects:

• -50 relations with other royal marriage partners
• -100 relations with the target country, and incur a loss of -20 prestige.
• Claimant gains "Claim on Throne" casus belli against the target. The war score cost to enforce a personal union is 84% regardless of the target's size.

Note that while some allies may be willing to join a conquest war, they will not join a claim on throne war or succession war, due to opposition to a successful personal union. The gained casus belli lasts until the target country produces an heir with a strong claim or a new heir rises to the throne or the royal marriage is ended.

The claim throne diplomatic action is only possible for Christian nations as no other religious group allows personal unions. While the Dutch republic, oligarchic republic, and elective monarchy can have royal marriages, their thrones cannot be claimed as they do not have heirs.

Support heir

Supporting an heir is an action that can be initiated on nations with an elective monarchy (which can only be gained by event for Poland and the Commonwealth, or by using a custom nation). Any nation that is in the same religious group as the country with elective monarchy can support an heir.

In an elective monarchy, each nation that has supported its heir in the current election cycle has a possible heir to the throne with an associated amount of support. A diplomat must be sent in order to support a nation's own heir in an elective monarchy,

The probability of increasing the heir's support every month by 1 is as follows:

$\%{\text{ probability of increase}}=5\cdot {\text{diplomatic reputation}}+5\cdot {\frac {\text{relations}}{100}}$

The elective monarchy may also increase support for its own heir by 5 points at the cost of -10 prestige. Upon the death of the elective monarchy's ruler, the heir with the most support rises to the throne in the elective monarchy.

If a foreign heir arises, the country that provided the heir gains:

• +25 prestige
• +10 legitimacy
• +24x administrative, diplomatic, and military power of the new ruler

If a local noble rises to the throne, the elective monarchy loses -20 relations with all countries that supported an heir in the election.

Covert actions

Main article: Espionage

Diplomats can be send to other nations to build up a spy network, or to practice counterespionage and increase the chance of catching spies sent by the target nation. When a spy network has grown enough, espionage actions can be undertaken, which do not require sending a diplomat. Most of the espionage actions require certain ideas from the espionage idea group in order to become available. Actions that do not need this group are fabricate claim, support rebels and justify trade conflict. Completing the espionage group will give access to various powerful actions. One example is the vetting idea, the first of the idea group, which grants a discount to technology cost depending on the difference in technology level between the home country of the spies and the target country, as well as the size of the spy network there. Covert actions are described in more detail on the Espionage page.

Economy actions

See also: Economy

Transfer trade power

Ask a target non-subject nation to transfer a percentage of its trade power to the proposer. While a transfer of trade power is active, the two nations involved cannot declare war on each other, and will also receive a mutual, scaling relation bonus (+20 if 100% of power is transferred). The agreement does not count towards each country's diplomatic relations limit. Even without , AI can be demanded to transfer trade power in a peace deal. Colonial nations automatically transfer trade power to their overlord.

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: +20
	Friendly: +10
	Hostile: -100
Proposer is not allied with or guaranteeing nation	-50
Nation opinion of proposer	+0.1 per positive relation
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. Increases for each percentage point 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

Steer trade power

Ask a target non-subject nation to use their merchants to steer trade toward the proposing nations trade capital. While a transfer of trade power is active, the two nations involved cannot declare war on each other, but unlike transfer trade power, there is no relations bonus. This effectively hi-jacks trade power in as many nodes as the target has merchants, where their merchants can be placed for the maximum benefit of the proposer. Technically, no trade power is transferred, so the values for each nation in each trade node remain the same, and if both share the same home node, then the target will still collect with their trade power, effectively wasting the value of the diplomatic agreement. The agreement does not count towards each country's diplomatic relations limit.

Issue embargo

Reduces the trade power of the target country in every 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:

	Traditions	Ideas	Bonuses	Policies
+25%	—	Espionage idea 6: Privateers	—	—
+10%	—	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	—	—

Knowledge Sharing

Gives the other country +1 monthly progress in its capital state towards the oldest institution the sending country has embraced that the other one hasn't embraced. This costs 10% of the receiving country's monthly income and lasts for 10 years, or until all the sending country's institutions are present everywhere in the receiving country's capital state.

This diplomatic option is not available for subject nations other than tributaries; only the overlord can share knowledge with them, and then only via the Knowledge Sharing subject interaction.

Send gift

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

${\text{relation bonus}}={\frac {2.4\cdot {\text{ducats gifted}}}{\text{monthly income of target country}}}$

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 it would increase relations more than previous gifts did.

Loan offer

Allows a nation 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. AI rulers will always decline unless they have one of the correct personalities.

Give subsidies

Transfer a specified amount of money each month to the target country for a certain duration. The sender may transfer between 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 per year. 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

${\text{yearly relations increase}}={\frac {12\cdot {\text{monthly subsidy}}}{\text{target countrys total monthly income}}}$

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.

Sell province

A province can be sold to an another nation for a price of 0 to 2,000 ducats at a cost of -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 only offer to sell isolated provinces, particularly if it is unable to core them. When the sell province button is clicked, the province to be sold can be chosen together with the price that will be asked for it.

Factors that influence an AI nation's willingness to buy a province:

Factor	Effect
Province is priced above current treasury of buyer	-1000
Buyer has no core or claim on province that is of a different culture group	-1000
Buyer has no core or claim on province that is of a different religious group	-1000
Buyer has no core on province and is currently overextended by any amount	-1000
Buyer has no core on province that is part of the Holy Roman Empire	-1000
Price	-1 for every 1% above above 50% of buyer's treasury
Province is adjacent to buyer	+10
Province has the same culture as buyer	+10
Province has the same religion as buyer	+10
Price	-100 to +100 based on development of target province

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

Additionally, it is not possible to sell a province to a colonial subject if the province is not in its colonial region. If the province is particularly undesirable to the buyer, then its base value and associated price modifier will both be halved.

Selling provinces to a vassal is one method of saving administrative power by letting the vassal core the province. It is useful for avoiding overextension in the short term, and exchanges immediate administrative coring costs for diplomatic annexation costs later. The 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 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).

Sell ships

Navies can be sold to other nations for a price of 0 to 1000 ducats. If the target nation accepts the proposal, the fleet in question will transfer its allegiance to the buyer. In order to be able to sell ships to a nation, both sides have to be at peace and cannot be rivals of each other. After pressing the button, the fleet that is to be sold can be chosen together with the asking price. When offered to buy a fleet, the AI will want to hold on to a certain ratio of ships (for example, most countries on the Atlantic coast don't want to buy galleys) and will never go above their naval force limit. In order to be able to sell ships, the buyer has to have a fleet within supply range of the target nation. Fleets outside of the receiving country's supply range are not available to sell. The mouse-over on the YES/NO bar will give the factors for their decision (shown below), and if the fleet being offered is too large, it specifies how many less they desire, allowing the player to exit diplomacy and structure a fleet that meets the target countries desired profile.

The factors that influence an AI nation's willingness to buy ships:

Factor	Effect
Attitude towards proposer	Friendly: +10
	Threatened: -20
	Loyal: +10
	Neutral: -10
Price	+50 to -200 depending on treasury of buyer and value of the ships
Buyer wants x fewer ship types	-10 per ship of undesired type
Diplomatic reputation	+1 per positive point, -1 per negative point

The AI will at times purchase obsolete ships. This makes it possible to get friends, allies, and subjects, as well as other non-rival countries to pay for upgrading the player nation's vessels when new models become available through advances in diplomatic technology. An aggressive nation may have trouble finding willing buyers and could potentially arm subsequent targets/victims, albeit with obsolete weapons.

Request to share maps

This allows a nation to ask another nation if they want to share the map of a region. If the nation accepts, the proposer will, at a cost of -15 prestige, discover all provinces that were not yet discovered in the specific region. The nation giving the map will receive 10. Nations can't be rivals of each other. In order to be able confirm the map exchange, the receiving nation has to have a unit stationed in a region adjacent to the specific region.

The factors that influence an AI nation's willingness to share maps are:

Factor	Effect
Distance between borders	+20 max
Easy	+10
Prestige of target nation	+0.25 per negative prestige
Rival's interest in region	50 max
Target nation's interest in region	-100 max
Target nation is a colonizer	-1000
Not the same religious group	-20 max
Attitude towards proposer	Friendly: +25
	Threatened: +20
	Hostile: -1000
	Unknown: -50
Nation opinion of proposer	+0.25 per positive relation
	-0.25 per negative relation
	-1000 if opinion -25 or lower
Diplomatic reputation	Positive: +5 per point
	Negative: -5 per point
Trust	+1 per point above 50 trust
	-2 per point under 50 trust
	-1000 if trust 30 or lower

Charter Company

This option allows a nation to purchase a province in a Trade Company region from another nation. Both nations must be at peace in order to negotiate the transaction. The player selects a non-capital province to purchase and moves the slider to increase the cash offered until the reasons to sell is one or more higher than the reasons not to sell. The more important the province to the owning nation the more reasons not to sell. Some of the factors are listed below.

• Base Reluctance -3
• Alliance +5
• Trust
• Diplomatic Reputation
• Province Development
• Province share of development
• Other provinces nearby 0 to -100

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: +20
	Defensive: +20
	Protective: +20
	Threatened: +20
	Neutral: 0
	Unknown: 0
	Hostile: -100
	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 empire. They will also seek access if they need to travel through a nation to fight in a war. 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.

Ask for 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 0.1 ducats per month per port, with a minimum of 0.5 ducats and maximum of 2.0 ducats. This fee is based on the amount 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 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: +20
	Defensive: +20
	Protective: +20
	Unknown: 0
	Neutral: -20
	Threatened: -30
	Hostile: -1000
	Outraged: -1000
	Rivalry: -1000
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

Main article: Papacy

Some diplomatic actions require control of the Curia and are also discussed on the papacy page. One of the diplomatic actions, call for crusade, allows the curia controller to call a crusade on a heathen nation. This will give every Christian nation bonuses if they are fighting in a war against the crusade target. The other action, excommunication, will grant every neighbor of the excommunicated ruler of a nation a free casus belli.

Emperor actions

Main article: Holy_Roman_Empire#Powers_of_the_Emperor

The Emperor of the Holy Roman Empire has several special diplomatic options available. These action are each explained in more detail on the Holy Roman Empire page.

Great Power actions

Main article: Great power

The top 8 high-scoring nations receive the Great Power status. For being a great power, you will unlock the following actions:

• Take on Foreign Debt – Pay off all the loans of the target independent non-great power country. Gives +10 relations bonus for every standard size loan of the target you clear, capped at +200, decaying -2/year. Also grants +5 trust and +2 favours (if The Cossacks is enabled). Requires enough money to pay off target’s loans.
• Influence Nation – Pay 1 year of target income to increase relations and grant +1 monarch points in their weakest category for 10 years in a target non-great power nation. This raises their opinion of the great power by +25 for the 10 years, also gives +5 trust. Going to war with them cancels this bonus.
• Intervene in War – If there is an ongoing war between three or more great powers but an imbalance in the number of great powers involved on each side, you can make it your business to intervene. For example, if great power England is singlehandedly fighting the great powers of France and Spain, you as a great power Commonwealth can intervene on England's side to balance out the number of great powers involved.
• Break Alliance – This will force a nation to break its alliance with another. They will accept if the target nation is sufficiently afraid of the player and you will gain a 10-year truce with the nation you forced this upon. Useful for stripping the war target of pesky roadblocks. The former ally gets a "Forced ally to break alliance" CB against the great power for 10 years. Both the target country and the former ally get a -50 relations modifier with the great power.

Note: nations who lose the status have access to the above actions for a grace period of 5 years.

Other

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

Select rival

The rival mechanic was added with patch 1.6.

Rivals are countries that a nation expects to come into conflict with in the future. Rivals are usually very comparable in military and diplomatic power and have interests in the same regions and thus will often clash with each other. Rivals may be only selected from countries that are comparable in power. When in the rival selection screen, the nations that are available as rivals and their corresponding opinion of the country and their relative army and navy strength can be seen. A country can have up to 3 rivals at the same time. If a rival becomes too weak or too strong it will cease being a valid rival. When selecting possible rivals, the game will take the relative army strength into higher account than the relative navy strength. Relative development and technology levels are also taken into accord. Nations must be relatively near to be eligible rivals, with more powerful countries able to have rivals at greater distance. Setting a nation as a rival will greatly decrease the amount of diplomacy that can be exchanged between the two nations. Rivals rarely accept diplomatic requests from their nemeses. In order to be rivals both countries must have each other discovered. Selecting a rival has the following benefits:

• A nation is more likely to sign alliances with the enemies of their rivals.
• +25% prestige from defeating a rival in battle.
• No trade efficiency penalty from embargoing the rival.
• +25% spy network build rate against the rival.
• −33% 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.

Changing a rival is possible after 25 years for 100 diplomatic power. The cost to change a rival may be reduced by 50% with the ‘Flexible Rivalries’ ability during the ‘Age of Absolutism’.

Release subject

This releases a country as a 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; the releasing country does not need to have cores on any of the provinces. Nations can only be released if at least one owned province is both a core of the nation and has its primary culture. This action can not be done while at war.

This is far more useful of an action than it looks like at first:

• Annex one or two provinces with cores of an extinct, but formerly large nation, and release that nation as a vassal. Then, you can slowly retake all their former land with the Reconquest CB, at no diplomatic point cost and only 25% of the Aggressive Expansion penalty.
• You should also do this if the nation is merely near death, but cannot be diplomatically vassalized for whatever reason. It causes more AE than forced vassalization, but the difference will not be significant if the country is small, and you will immediately have a vassal with low liberty desire and a good opinion of you, instead of large penalties from forced vassalization and aggressive expansion.

Achievements

Subsidize my Love Subsidize 3 different allies at least 50% of their monthly income without running a deficit.

The Continuation of Diplomacy Successfully use Threaten War to gain a province from another nation.

Until death do us apart Secure a Royal Marriage with another country.

Footnotes

Diplomacy