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EU4 Beginner Tutorial #4 - War. A complete beginner tutorial with MordredViking looking at how warfare works in the game.

Warfare is one of the primary ways to obtain territory and other concessions from other nations. The technical aspects of maintaining a military machine and its employment on the field is discussed in-depth in the articles land warfare and naval warfare.

Starting a war[edit | edit source]

Like most diplomatic actions, declaring war requires a diplomat. War may not be declared on an ally, a subject, a guaranteed nation or a nation transferring you commercial power without first breaking that relation.

Casus belli[edit | edit source]

Main article: Casus belli

The aggressor may pick a casus belli when declaring war. This determines the wargoal, the options available in the subsequent peace deal, and their associated costs in warscore, aggressive expansion, and diplomatic power.

Declaring War with a Casus belli

No casus belli[edit | edit source]

Declaring war without a casus belli will result in -20 Aggressive expansion impact.png aggressive expansion, a -2 drop in Stability.png stability, and +2 War exhaustion.png war exhaustion. These penalties are halved with full Diplomatic ideas.

Good relations[edit | edit source]

A country declaring war on another whose opinion of them is higher than 100 will cause -1 stability and +1 war exhaustion. If opinion is higher than 150, penalty increases to -2 stability and +2 war exhaustion.

Co-belligerence[edit | edit source]

If a country is not marked as a co-belligerent:

  • That country can't call its allies to arms in that war (but its subjects are called as normal). Beware that the Holy Roman Emperor defending the empire is always a co-belligerent.
  • Taking that country's provinces in a peace incurs Aggressive expansion impact.png +50% aggressive expansion and costs War score.png +100% warscore.

If a country is marked as a co-belligerent:

  • That country can call on its own allies to fight as well
  • If that country has a guarantor, it is also called to war
  • Taking that country's provinces will cost the same as the war leader's provinces

Note: If a nation is marked as a co-belligerent, but are also a tributary of another nation, neither the tributary overlord, nor the co-belligerent's allies will be called in. A similar loophole also applies in the HRE. If a free city or an HRE member is marked as a co-belligerent neither the Emperor nor the Emperor's allies will be called in. But in this case the allies of the co-belligerent will be called.

Things you cannot do while being at war[edit | edit source]

Note that while your country is at war you cannot do quite a lot of things:

Following diplomatic actions are no more possible to use with countries that become your war enemies until war ends:

Also, when your country is fighting offensive war AI will reject any alliance offers from you.

Sides in a war[edit | edit source]

A war consists of two opposing sides of one or more countries. A side may be made up of a coalition, the emperor, allies or the defender of the Faith who honour their treaties and/or vassals and other subject countries.

War leader[edit | edit source]

The war leaders are denoted with a star in the war screen. The war leader on the attacking side is the country that declared the war, while on the defending side the leader is the country on which the war was declared (the target of the war goal). For each side in a war the leader is the country that may call in its allies and may negotiate peace on behalf of all their war allies, simultaneously ending the war for everybody. They may negotiate a separate peace with each of the hostile belligerents, except subject nations or coalition members. They may surrender territory of their war allies, but not their treasury.

When a war leader is annexed in a separate war, one of their allies will become the new war leader. The new war leader can call their own allies into the war if the war has not lasted long enough to close the window for calling allies to it. If the war leader is vassalized (by event or force) the new overlord will become the new war leader and can call their allies with the same caveat about calling allies to long wars.

Military and port access[edit | edit source]

All nations on the same side in a war have military access to each others' lands. They may also dock at each others' ports, although their fleet supply range will not be extended. Furthermore, all participants have military access to all nations that have given access to any participant, and all participants in a war involving the Holy Roman Emperor have access to all members of the empire.

Joining a side[edit | edit source]

After a war has started, a country usually cannot join any of the sides unless called in later. There are three exceptions to this rule. The enforce peace action allows for a country to force the attacking war leader to sign a white peace. If the attacker does not accept, the enforcer will join the war on the defender's side. Additionally, a country that subjugates a participant will join the war on its new subject's side. Finally, with Rights of Man.png Rights of Man, a great power may intervene in a war involving at least three other great powers on the side that has fewer great powers.

A way of indirectly fighting in a war is for a country to rent out condottieri to one of the countries involved.

Fighting a war[edit | edit source]

Main articles: Land warfare, Naval warfare

War may be fought on both the land and the sea. See the appropriate articles for more information.

War exhaustion[edit | edit source]

Main article: War exhaustion

War exhaustion represents the will of a country's population to fight. High war exhaustion will sap the ability of a country's armies to fight and reinforce.

Call for peace[edit | edit source]

If the warscore is substantial (66.6%+) and it has been at least 5 years since the war was declared, a country's abstracted population may call for peace. This modifier increases the nation's monthly War exhaustion.png war exhaustion, beginning at +0.005 per month, and ticks up by another +0.005 per month indefinitely. This means a call for peace will eventually start increasing a country's war exhaustion even if it has a monthly reduction, e.g. from being Defender of the Faith, having the 6th Innovative idea, or having the Kind-Hearted ruler trait. Only human players get call for peace.

Call for peace will also occur if the country fails to submit a peace offer within 3 months of an enemy surrendering unconditionally. In this case the ticking war exhaustion begins at +0.05 per month and increases more quickly.

Warscore[edit | edit source]

Warscore is the means of measuring whether a war is going in the favor of the aggressor or the defender. It is a common metric used across a number of Paradox Interactive titles, including Europa Universalis III, EUIV, Crusader Kings III and Victoria II.

The scale ranges from +100% (a complete victory for the side currently being viewed) to −100% (complete defeat for the side currently being viewed).

Warscore is measured using a number of different parameters:

  • Occupied provinces
  • Battles won or lost, to a maximum of 40% in either direction.
  • Blockaded ports
  • Met war goals. A met war goal will cause war score to gradually tick up for whichever side has met it, to a maximum of 25%.

Note that both sides have symmetrical war goals. It is possible for no one to have met the goal; in particular, Show Superiority warscore won't tick if neither side has more than 10% warscore from battles, and a province goal won't tick if a third party (e.g. rebels) controls it. Hence, for provinces that are being colonized and yet are the war goal, rather seize them for yourself during the war, otherwise the enemy may destroy or abandon them and the target will then cease to exist – unable to provide a ticking war score.

Occupation[edit | edit source]

Occupation is the term used to describe when a province has been successfully taken over by an enemy country. It requires the successful siege or assault of the local fortification. Upon occupation of a province, the owner of the province can no longer use the province for many purposes:

  • Regiments, ships and buildings can no longer be built in the province, and any unit or improvement building that was underway (including cores and religious or cultural conversion) is immediately halted.
  • All province income and trade power is no longer given to the owner; a portion of the province's production income and trade power is now given to the occupier.
  • The owner can no longer use the province for a fleet base; any ships currently in the port are forced out to the adjacent sea zone. The controller does have access to these ports.
  • The province does not count for the owner for calculating naval supply, colonial range and trade range. This is important, as one may have to unsiege certain provinces far away in order to take provinces in a peace deal (due to lack of colonial range). Force limits are unaffected.
  • The controller of the province can recruit mercenaries there.
  • Occupied forts project a zone of control over unfortified land owned by countries that aren't allied to their occupier.

Transfer occupation[edit | edit source]

Countries can give up control over occupied provinces to their allies in war. (The Transfer occupation.png ‘transfer occupation’ button is located on the province screen.) This will make it possible to ensure that nations are rewarded for their participation in the war.

If you called an ally in with a promise of land, you may often find in the peace deal that they "do not want" the province in question - even if they highlighted it as a "province of interest" in the Diplomatic Feedback window. Hence, they will lose trust in you if you take any land or war reparations. However, there is a solution: before you peace out, make sure that ALL the land they highlighted as "province of interest" are under their control (hence you have transferred occupation to them), then even if you give them nothing, they will not lose trust in you (shown as a thumbs down warning in the peace menu, instead it will be neutral).

Administrative efficiency[edit | edit source]

Main article: Overextension#Administrative efficiency

Administrative efficiency is a country wide bonus that is unlocked at administrative technology level 17 and increases at 23 and 27, up to a total of 30%. Additionally Absolutism.png Absolutism provides additional administrative efficiency scaling with amount, up to 30% at 100. Administrative efficiency directly reduces core creation and diplomatic annexation costs, as well as the impact of province development on overextension and warscore cost, allowing for much larger territories to be conquered at once.

Sue for peace[edit | edit source]

Peace interface, on the "Demand tribute" tab.

This option will open the peace negotiation screen where the country 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 country can get more out of the war by picking off participants one by one.

Unconditional surrender[edit | edit source]

Upon offering unconditional surrender, all of the currently unoccupied provinces will fall under enemy control and the enemy will gain 100% warscore. Armies of the country that surrendered will become exiled and unable to fight in future battles until peace is signed. For the recipient of an unconditional surrender, it will be alerted of the enemy’s surrender and from then on will be able to enforce any possible peace up to 100% warscore cost. If the recipient country does not sign peace after a couple months, they will get call for peace giving them monthly war exhaustion which increases faster than normal. The peace will be automatically accepted by the nation that surrendered. In some circumstances the AI will unconditionally surrender.

Peace terms[edit | edit source]

Each term in a peace offer has an associated cost in warscore, Prestige gain/loss for both sides and possible aggressive expansion for anyone making sizable, selfish demands. An appropriate casus belli may modify any or all of these values, and is required to enable certain terms. A country making peace separately may only accept terms relating to itself and its subjects, not other participants in the war.

Demand War score.png Warscore Yearly prestige.png Prestige Aggressive expansion impact.png Aggressive Expansion Effect
Annex province Province cost 0.25 per development[Note 1]; some overseas provinces give less prestige 0.6 per development[Note 2] The selected province of the country on the losing side is annexed by its current occupier, or by the country making peace if not occupied. If it is occupied, the occupier must be one of the parties to the peace. If a CB with the "Take province"(e.g. conquest or reconquest) or "Take colony" wargoal is used, the warscore cost for the wargoal is lowered by ⅓ if it is occupied(this does not apply to CBs with the "Take capital" wargoal). In a coalition war, members of the coalition may only take their own cores. AI won't accept giving away unoccupied forts, or unfortified provinces that are near forts if none of them are occupied.
Revoke core Half province cost 0.1 per development[Note 1] 0 The loser revokes their core on the selected province that they don't own before the peace. Revoking cores of third parties gives them a small relations bonus towards the winner. Never costs diplomatic power.
Return core Province cost 0.25 per development[Note 1] 0 The loser returns the selected core province of an existing country, and loses their core if the province is not of their primary culture. The victor may lose claims on provinces returned to other nations.
Concede Colonial Area Sum of province costs 2[Note 1] 0.2 per development[Note 2] Requires The Cossacks.png The Cossacks and a colonial nation with a province in that colonial region. The loser cedes all provinces in the selected area to the winner or the winner's colonial subject if one exists. Furthermore, the loser may not establish any additional colonies in the region unless they overturn the peace treaty in another war with the victor. Can't be used against unreformed natives.
Give up claims 20% 2 0 Requires Art of War.png Art of War. The loser revokes all claims on the selected country, who need not be involved in the war. If it's a third party, this gives them a small opinion bonus towards the winner.
Cancel subject Half of the sum of the province costs of the subject 0.25 per development of the subject[Note 1] 0 The selected subject of the loser becomes independent. Cannot cancel Trade Companies or Colonial Nations.
Release nation sum of province costs 0.25 per development[Note 1] 0 A new nation will be formed out of the loser's provinces with cores of that nation. The new nation will be included in the resulting truce. The new nation will have its capital's religion and culture. The loser also loses their cores except on provinces of their primary culture.
Force religion Sum of province costs[Note 3] 10 0 Loser converts state religion and religion of their capital to that of the winner[Note 4]. Only possible within the same religious group(except when using the Great Holy War CB); that is, only heretics can be converted, not heathens.
Form Personal Union 60% 20 0.2 per development[Note 2] Loser becomes lesser partner of a Personal union.png personal union with the winner. Only available with "Claim on Throne" and "Restoration of Union" CBs.
Become vassal Sum of province costs 1 per 2 development 0.5 per development[Note 2] Capped at 200 Dip Points. Loser becomes a Vassal.png vassal of the winner.
Become tributary Sum of province costs 1 per 2 development 0.5 per development[Note 2] Requires Mandate of Heaven.png Mandate of Heaven. Loser becomes a Subject tributary icon.png tributary of the winner. Only available for countries capable of making tributaries.
Pay tribute 5% per loan 0.5 per loan 0 Loser pays an immediate lump sum of Gold Icon.png ducats to the winner, measured in amount of loans. Limited to 5 loans, and results in inflation for the winner. Quick rule of thumb is 2.75 ducats x Total Development of Target nation [as can be seen in the Ledger under the Country tab].
Concede defeat 10% 10 0 A "white peace plus", the only change being a larger gain and loss of prestige than other peace deals such as paying gold (±10 instead of ±2). Not compatible with any other terms. Can only be used between the war leaders.
Annul treaties 10% 1 0 Loser cancels all treaties (including military access) with the selected country, and is not allowed to sign any new treaties with that country for a duration of 10 years. Royal marriages are unaffected.
Change government 50% Loser's government type changes to that of the winner. Only available with Government Type and (unused) Revolutionary War CBs.
Transfer trade power 30% 1 0 Requires Wealth of Nations.png Wealth of Nations. Establishes a "Transfer Trade Power" relationship from the loser to the winner, amounting in 50% of the trade power in all trade nodes where both countries have trade power. This lasts until cancelled, which the loser can't do until the truce expires. Transfer Trade Power does not occupy a relationship slot.
Steer trade 60% 2 0 Requires Rule Britannia.png Rule Britannia. Establishes a "Steer Trade" relationship from the loser to the winner, forcing them to use their merchants to steer trade towards the winner.
Humiliate 40% 5 0 Winner gains Power projection.png 30 power projection, loser loses Power projection.png 30 power projection. Note that the power projection bonus from humiliating any one rival caps out at 30; and doesn't stack, instead refreshing the bonus. Only available if the loser is the winner's rival.
Show strength 100% 0 0 Winner gains Power projection.png 30 power projection plus All power costs.png 100 of each monarch power, loser loses Power projection.png 30 power projection and Yearly prestige.png 20 prestige. Note that the power projection bonus from humiliating any one rival caps out at 30; and doesn't stack, instead refreshing the bonus. Only available with the "Humiliate Rival" casus belli.
War reparations 10% 2 0 Requires Art of War.png Art of War. The losing party is forced to pay 10% of their income to the winning party as war reparations. This lasts for 10 years. It is canceled if you go to war with the same nation again.
Force migrations 100% 2 0 Requires Conquest of Paradise.png Conquest of Paradise. Force a primitive nation to migrate elsewhere. Only possible when the nation is small enough.
Enforced military access 15% 0 0 Force a nation to give military access until truce expires.
Enforced fleet basing rights 25% 0 0 Force a nation to give fleet basing rights until truce expires.
Enforce rebel demands 50% 2 0 Force a nation to accept the rebels' demands. Only works with the "Support Rebels" casus belli (requires Art of War.png Art of War).
Religious Supremacy 50% 37 0 Attacker's religion becomes the official religion of the Holy Roman Empire. Available only with the "Religious League" casus belli (requires Art of War.png Art of War).
Claim Mandate of Heaven 50% 25 0 Attacker becomes the Emperor of China. Available only with the "Take Mandate of Heaven" casus belli (requires Mandate of Heaven.png Mandate of Heaven).
Dismantle the Revolution 100% 25 0 Defender stops being the revolution target and becomes a monarchy. Available only with the "Crush the Revolution" casus belli and as a defender against the "Spread the Revolution" casus belli.
Extinguish the Revolution 20% 3 0 Only available if a Revolutionary war was declared but the target ceased being revolutionary during the war. Removes the Revolution from all provinces of the target and awards 100 of all Monarch power.
Spread the Revolution 60% 0.1 per target development 0 Requires the Emperor Emperor DLC. Available only with the "Spread the Revolution" casus belli and as a defender against the "Crush the Revolution" casus belli. Gives 0.1 Revolutionary zeal.png per target development and ⅓ monarch point in every category per target development. The revolution will spread to all provinces of the target.
Expand Empire Provinces x 1.25 0.06 per development 0.08 per development Only available to the Emperor after the "Absolute Reichstabilität" reform has been passed. Forces defender, all their subjects, and all their provinces to join the empire. Attacker gains Imperial Authority equal to 0.1 x Defenders Developement
Reintegrate into the Empire 80 1 per warscore 0 Only available to the Emperor during the Swiss war for Independence. Forces defender, all their subjects, and all their provinces to join the empire. Attacker gains 25 Imperial Authority.
Grant Independence 30%[Note 5] 0 0 Only available for subjects with the Independence, Colonial Independence, War for the Emperor CBs.
Raid Heretic Churches 20% 2 0 Only available for countries with the "Salvific Plutocracy" Government Reform

Destroys the Latin temple.png church or Latin cathedral.png cathedral in a province. Gain Church power.png 50 church power or Monthly fervor.png 25 fervor and loot the province. The province to raid is the first province in the following list which has a church or cathedral:

  • Roma (118)
  • a random province which has at least Development.png 40 development
  • a random province which has at least Development.png 30 development
  • a random province which has at least Development.png 20 development
  • a random province which has at least Development.png 10 development
  • a random province
Claim Norwegian Throne 60% 60 0.35 per development[Note 2] Forms a Union with Norway. Only available to Flag of Sweden Sweden via Mission
Claim Electorate 40% 40 0.35 per development[Note 2] War is declared against the Emperor to take the Electorate from one random Subject of yours.
Establish Eyalet Sum of province costs (maximum of 60) 1 per warscore 0.4 per development Loser becomes a Icon eyalet.png Eyalet of the winner. Only available to the Flag of Ottomans Ottomans and Flag of Rûm Rûm
Annex Migratory Tribe Sum of province costs (maximum of 100) 0.1 per development 0.1 per development Annexes all currently inhabitated provinces of the tribe. The tribe will not be able to migrate and ceases to exist.
  1. 1.0 1.1 1.2 1.3 1.4 1.5 The prestige from this peace term is reduced by the administrative efficiency
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Aggressive expansion is modified by many factors. See the article about aggressive expansion for details. The AE impact for the different peace terms is specified in /Europa Universalis IV/common/peace_treaties if there is a file for the peace term. For hardcoded peace terms the AE is specified in /Europa Universalis IV/common/defines.lua.
  3. Some ideas and bonuses reduce cost to force religion
    Cost of enforcing religion through war Traditions Ideas Bonuses Policies
    • Divine idea 5: Alpha and Omega
    • Genevan idea 3: The Home of John Calvin
    • Trent ambition
    The Global Crusade -50% Tier 12 Government Reform for Theocracies
    Salvific Plutocracy -33% Tier 1 Government Reform for Theocracies
    Millennialist Theocracy -10% Tier 1 Government Reform for Theocracies Domination.png
    Cologne cathedral -10%/-25%/-33% Monument at Noteworthy/Significant/Magnificent Level
    Registan Square -5%/-10%/-15% Monument at Noteworthy/Significant/Magnificent Level
    Shinto Warriors -50% Reward for Flag of Japan Japan mission "A New Buddha?"
    Realm of One Faith -75% for ~30 years Reward for Flag of Ottomans Ottomans mission "A [Root.Religion.GetName] [Root.GovernmentName]"
    Enforcers of Religious Superiority -50% for 25 years Reward for Flag of Sweden Sweden mission "Catholic Bulwark"/"The Protestant Sword"
    Catholic Supremacy -25% for 25 years Reward for Flag of France France mission "French Wars of Religion"
  4. if the capital changes because the old capital is taken in the peace deal, the religion of the old capital is converted
  5. the warscore cost for Grant Independence is reduced by 25% with the Independence and Colonial Independence CBs.

Unjustified demands[edit | edit source]

Unjustified demands.png Unjustified demands are peace terms that are not part of the wargoal. They will cost 2Diplomatic power.png per development of affected provinces[1]:

  • Annex province
  • Return core
  • Cancel subject
  • Release nation
  • Force vassalization

The diplomatic power cost of unjustified demands can be reduced by:

Unjustified demands.png Traditions Ideas Bonuses Policies
  • Full Influence
  • Creek traditions
  • Kikuchi traditions
  • Siberian traditions
  • Aristocratic idea 6: Rightful Conquest
  • Barbary Corsair idea 6: Heirs of Al-Andalus
  • Latin idea 6: Partitio Graeci
  • Moravian idea 7: Legacy of Great Moravia
  • Piratical ambition
  • Kitaran idea 4: Lakes Dominance
  • Perugian idea 7: The Baglioni Dream
  • Colognian ambition
  • Nagpuri idea 7: Unjustified Expansion
  • Imagawa idea 7: March to Kyoto
  • Autocracy reform (Monarchy tier 1): −10%
  • Ottoman Government reform (Monarchy tier 1): −10%
  • Demanding provinces from a rival: −33% for annexing provinces only
  • Flag of Venice Venice mission Destroy Austria: −10%
  • China temple.png Commanderies of the Five Armies faction in power in the celestial empire without the Mandate of Heaven.png Mandate of Heaven DLC: −25%
  • Being the revolutionary target: −50%
  • Modifiers to All power costs.png all power costs also apply additively
  • Taking provinces from primitive countries doesn't cost any diplomatic power[2], but this doesn't apply to tribal land.

Note that forming a separate peace can incur a Diplomatic power.png diplomatic power cost, since there is effectively no casus belli when not negotiating with the war leader.

Distribution of spoils[edit | edit source]

Shows distribute spoils in game.

Spoils of war are distributed between its participants with prestige and money going to the belligerents of the war based on their war contribution rather than only to the war leader. For example, if Spain and France fight in a war against Great Britain and France gets 70% war contribution and Spain 30% then the prestige and money will be divided so that 70% goes to France and 30% goes to Spain.

Truce[edit | edit source]

Once a peace deal is accepted, it results in a state of truce between every country on the offering side and every country on the accepting side. Specifically, when a country other than a war leader accepts peace, or offers a peace deal the other side's war leader accepted, it enters truce with every enemy country still in the war, but its war allies are not affected.

The duration of the truce depends on the amount of warscore that was used to demand or offer tribute in the peace deal. The formula is

so a white peace will result in a 5-year truce, whereas a peace deal at 100% war score will produce a 15-year truce. When a country is released in a peace deal, it starts with a 5-year truce with both the releasing nation and the opposing war leader.

A country cannot embargo or join a coalition against a country it has a truce with, though ongoing embargoes are unaffected. A country with a truce also cannot be designated co-belligerent. It can still declare or join a war with the country with a truce, but with the following consequences if it is an offensive war:

Ideas Stability.png Stability War exhaustion.png War exhaustion Aggressive expansion impact.png Aggressive expansion
Normal −5 +5 −50
Full Diplomacy −3 +3 −30

These stack with the penalties for other reasons. So attacking in breach of a truce without a CB and without full diplomacy results in −7 stability, +7 war exhaustion and −70 aggressive expansion. As seen above, breaking a truce has very negative effects when declaring war or joining an offensive war against a country with whom a truce exists. The AI has −1000 reasons to join an offensive war if they have a truce with the defender and appears to never declare war, join as an ally in an offensive war, or call an ally into an offensive war if that would break a truce. Joining defensive wars, or where the country with a truce is a secondary participant, does not give a penalty.

Revanchism[edit | edit source]

An example of revanchism.

Revanchism is a mechanic that helps prevent a "death spiral" after losing a war where a country would go bankrupt, lose manpower and have huge revolts, followed by other countries declaring war as well, leading the nation to ruin. Revanchism is gained from losing provinces in a war and scales in direct correspondence to the war score taken in a peace deal, with a max of 100% revanchism at 100% warscore. Revanchism decreases at a rate of 10% per year. Releasing nations and returning cores does not grant revanchism.

With maximum revanchism of 100% (from having 100% warscore worth taken in a peace deal), a country gets the following modifiers: [3]

National tax modifier.png +50% National tax modifier
Fort defense.png +25% Fort defense
Manpower recovery speed.png +50% Manpower recovery speed
Yearly army tradition.png +1% Yearly army tradition
Yearly navy tradition.png +1% Yearly navy tradition
National unrest.png −5% National unrest
Interest per annum.png −1% Interest per annum
Yearly horde unity.png +10% Yearly horde unity

These modifiers scale linearly with revanchism from 0% to 100%.

Note that revanchism caps out at 100%, even if a peace deal worth more than 100% warscore in total was taken (such as in multiplayer that allows peace deals over 100% warscore or from multiple peace deals).

Full Annexation[edit | edit source]

Upon annexing all of the provinces of a participant of a war in a peace deal, all subject nations of the annexed nation except personal unions become subjects of the annexing nation. This costs nothing above the cost of annexing the overlord. Junior partners of the annexed nation become independent instead.

Negotiating peace[edit | edit source]

Human players are largely free to accept or refuse any peace deal. However, as with other diplomatic actions, the AI will accept a peace deal if and only if it has more positive than negative reasons to do so.

Warscore[edit | edit source]

The warscore is of primary importance. Each point of warscore will give +1 reason for the AI to accept a peace deal, whereas each warscore cost of the peace terms will give −1 reason for the AI to accept a peace deal. The AI will refuse all demands if individual warscore is less than 10.

Demands exceeding warscore will give additional negative reasons for the AI to accept the peace deal, up to −100 at 99% warscore and lower. Demands exceeding 100% warscore will give −1000 reasons (unreasonable demands, not to be confused with Unjustified demand). Individual demands that would cost over 100% warscore, such as vassalizing a country that is too large, can't be selected.

If one side of the war has 100% warscore, the country is forced to accept any peace offer of 100% or less warscore. This also applies to losing human players. Note that 100% warscore only happens when one side fully occupies the other and is itself completely unoccupied. Otherwise, warscore is capped at 99%.

Regardless of warscore, the AI may refuse peace deals that contain terms that they do not desire; for example, provinces they will be unable to core. Such offers cannot be submitted (the "Send Demand" button is greyed out). The only exception is stated above, where the AI is forced to take a province they are unable to core if the other side has more than 100% warscore.

If you called an ally in with a promise of land, you may often find in the peace deal that they "do not want" the province in question - even if they highlighted it as a "province of interest" in the Diplomatic Feedback window. Hence, they will lose trust in you if you take any land or war reparations. However, there is a solution: before you peace out, make sure that ALL the land they highlighted as "province of interest" are under their control (hence you have transferred occupation to them), then even if you give them nothing, they will not lose trust in you (shown as a thumbs down warning in the peace menu, instead it will be neutral).

Province cost[edit | edit source]

Each province that changes control in a peace deal requires a corresponding Province war score cost.png warscore cost. The factors that influence each province's warscore cost are:

Base 5 per province.
Development 1 per development, cap at 30
Trade power 0.2 per base trade power (before modifiers applied)
Capital 0.2 × (5 + development) if the province is a capital
Local autonomy −0.33% per percentage point
Size of nation −1% per 15 development of nation (owner)
Administrative efficiency −1% per point of the annexing country's Administrative efficiency.png administrative efficiency

The local autonomy, size of nation and administration efficiency factors are applied multiplicatively.

The following ideas reduce province warscore cost:

Province war score cost.png Traditions Ideas Bonuses Policies
  • Diplomatic idea 6: Flexible Negotiation
  • Indigenous idea 7: Treaties Kept
  • Asturian idea 1: Reconquista
  • Evenk traditions
  • Thüringian traditions
  • Acehnese/Pasai idea 3: Rise of Aceh
  • Desmondian idea 4: The Munster Ambition
  • Montferrat idea 7: Last Claimants of Byzantium
  • Oda idea 2: Tenka Fubu
  • Saxe-Lauenburg idea 3: Niedersachsen
  • Ito idea 4: Anti-Shugo Movement
  • Qara Qoyunlu idea 2: Governor of Azerbaijan

Province warscore cost are also modified by:

  • −10% for having claimed Military hegemony
  • −15% for 20 years by completing Conquer Cuttack Bengali mission
  • −15% until the end of the campaign by completing Defeat the Rus Mongol mission
  • −15% for assimilating the Slavic culture group with the Mughal Diwan government reform.
  • −20% for 20 years by completing Devastate China Manchurian mission
  • +200% with Privilege grant autonomy.png Inwards Perfection church privilege (scaling to the estate's land ownership)

If a province has a different religion than the new owner (cede province) or the nation suing for peace (treaties), the War score cost vs other religions war score is further affected by:

One State under God −30% Tier 12 government reform for Government theocracy.pngTheocracies, except for countries with religion Pagan religion group
Religious Wars −25% Age of Reformation.png Age of Reformation ability
Sword of Islam −25% for 20 years from Andalusian mission: Restore al-Andalus
Defender of Africa −15% from Kongo mission: Protector of Africa
Militarists in Power −15% Available for Government theocracy.pngTheocracies with Tier 9 government reform "Open public Elections" and Militarists in power
Persian Revenge −15% Flag of Aksum Aksum national idea 3
Sola Scriptura −10%Hussite Hussite Religious aspect
Catholic Mysticism −10% CatholicismCatholic Harsh Concession in the Council of Trent
Monument in Malta −5% / 10% / 15% holding Great project malta forts.pngMalta Forts at 24px/File:Great project level icon tier 1.png Noteworthy /24px/File:Great project level icon tier 2.png Significant /24px/File:Great project level icon tier 3.png Magnificent level (only with Leviathan.png)
Monument in Mecca −5% / 10% holding Great project kaaba.pngKaaba at 24px/File:Great project level icon tier 2.png Significant /24px/File:Great project level icon tier 3.png Magnificent level while province religion is in Muslim group and same as owner (only with Leviathan.png)

War enthusiasm[edit | edit source]

Other factors also give reasons for the AI to accept or refuse a peace deal. These are summed up as war enthusiasm in the war screen. Positive War Enthusiasm is applied as negative reasons for that country to accept peace deals.

  • Length of war: +45 at start of war, decays by −0.75 at the start of each calendar month thereafter (5 years until it becomes negative).
  • Casus belli "Religious League" and "Crush the Revolution": +50
  • Casus belli "Coalition": +30 for attackers
  • Relative strength of alliances: −20 to +20 for war leader only
  • Ally in war: +10 for allies called in by war leader, +50 for Holy Roman Emperor (defensive war)
  • Military strength: −20 to +20, depending on proportion of manpower and land force limit that is filled, as well as battles lost or won
  • Recent gains: −20 to +20 for war leader only.
  • Hold their own capital: +5
  • War exhaustion: −1 per point of war exhaustion
  • Occupied and besieged provinces: scales linearly with base tax of provinces affected, up to −20 for full besiegement, and −40 for full occupation. The formula is roughlyColonies and distant overseas provinces are ignored in this calculation.
  • Revolts in country: depends on the size of all rebellions relative to current military strength. The formula iswith the final number rounded to the nearest integer and capped at −20.

If war enthusiasm is between 0 and 20 it's classified as medium; below 0 is low and above 20 is high.

Stability hit[edit | edit source]

If a player refuses a peace offer that entails demands for less than 50% of the current warscore, and the warscore itself is higher than 50%, the declining party takes a −1 hit to Stability.png stability. When a player is already at −3 Stability.png stability, any qualifying offer is automatically accepted on behalf of the player. There is a Diplomatic power.png icon displayed above the 'send peace request' button which shows that if the player refuses this peace, they will lose stability

This mechanic aims to prevent players from unreasonably dragging out lost wars to harm their opponents (by deliberately causing war exhaustion to rise or rebels to spawn).

The AI has other rules for accepting peace deals and does not get a stability hit.

Footnotes[edit | edit source]

  1. From /Europa Universalis IV/common/defines.lua: PS_DEMAND_NON_WARGOAL_PEACE = 2.5 (this value is rounded down to 2)
  2. From /Europa Universalis IV/common/defines.lua: PS_DEMAND_NON_WARGOAL_PEACE_PRIMITIVES = 0
  3. See in /Europa Universalis IV/common/static_modifiers/00_static_modifiers.txt under recovery_motivation(Static modifiers#Revanchism).

Concepts CorruptionGoverning capacityOverextensionPower projectionRebellionRegionsStabilityStates and territories
Court AdvisorsConsortMonarch powerNational focusRulerRuler personalities
Estates and Factions FactionsEstates (Base estates (BurghersClergyNobility) • Cossaks estates (CossacksDhimmiTribes) • Dharma estates (BrahminsJainsMarathasRajputsVaishyas) • Domination estates (JanissariesEunuchs))
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