Subject nation

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The subjects interface panel image as of patch 1.18

Subject nations are semi-independent subordinate nations that surrender their economic, diplomatic and/or military power to another country in exchange for protection by their overlord. It is possible to see a subject's nation information by selecting the country icon on the subjects tab. The types of subject nations range from the primarily economic Subject tradecompany icon.pngTrade company to the military-focused March icon.pngMarch. All subjects (except trade companies) have a Liberty desire.pngliberty desire that determines their loyalty towards their liege.


Main article: Vassal

Vassal.png Vassals are the most basic form of subject nations. They are required to pay a portion of their Income from vassals.pngtax income to their overlord but do not transfer Trade power.pngtrade power to their overlord like other particular subject types(vassals of a merchant republic transfer 50% of their trade power to their overlord if Wealth of Nations.png Wealth of Nations is active). While vassals may have control over their own territory and military, they also automatically join any conflict their overlord enters into.

Vassalization can occur militarily by forcing it upon a defeated enemy in a war. Diplomatic vassalage can occur if a military alliance exists and relations are high (above 190). Vassals cannot declare war, and fabricate claims that either they or their overlord deems as 'Vital Interest'. Vassals with over 50% Liberty desire.pngliberty desire can request a support of independence from other nations, and break free through an independence war. Vassals with over 50% Liberty desire.pngliberty desire are also more active diplomatically as to forming their own alliances and setting more provinces as those of interest.

After a nation has been a vassal of another country for at least ten years, their overlord can begin diplomatically integrating them into the overlord's domain. This results in the vassal's annexation.


Main article: March

A March icon.png march is a militaristic vassal that cannot be annexed and does not pay taxes to the overlord, but has lower liberty desire and gets significant bonuses to its armed forces.

Marches receive increased Land force limit modifier.pngland and Naval force limit modifier.pngnaval force limits, National manpower modifier.pngmanpower and Manpower recovery speed.pngmanpower recovery speed, and Fort defense.pngfort defensiveness, while also gaining decreased Fort maintenance.pngfort maintenance.

March status can be revoked and the subject turned into a simple vassal but at the cost of stability and relations loss.

Client state

Main article: Client state

Client states are highly loyal, custom vassals. They can be formed once a country reaches Diplomatic tech.png diplomatic tech level 23 from any province or provinces that the player has control over.

Generally, any province within two tiles by land can be added to a client state, including over straits. The first province that a new client state is given is automatically designated as the capital, and the Culture icon.pngculture in that province will become the primary culture of the new client state. The client state will have its creator's state religion.

It is possible to customize the flag and the name of a client state based on a set of flag templates and images.

Nevertheless, if you make your client state into a march, customization (such as flag, name, map color) won't be available until you convert it back to vassalization.

Personal union

Main article: Personal union

Junior partners in a personal union share the same ruler as that of the leading country. Like vassals, junior partners of a personal union will automatically go to war if their overlord does, but they do not have to provide their overlord with a percentage of their monthly income, and only get a small +10 Icon diplomacy relations.png relations boost with their overlord. The junior retains any subjects it had, except other unions, which the overlord inherits.

Personal unions can occur when a ruler dies without a legal heir. In this case, if a royal marriage partner shares the same dynasty as the deceased ruler, it becomes the senior partner in a union. A succession war may erupt between rivals or valid partners. Additionally, a claim throne casus belli can be used on nations with a disputed succession (weak or no heir) of the same dynasty that the player has a royal marriage with.

Personal union partners can be inherited or integrated provided the union has been stable for fifty years. Diplomatic integration annexes the junior partner at the cost of Diplomatic power.pngdiplomatic monarch points. Inheritance automatically annexes the junior partner with no autonomy, but occurs only upon ruler death. The probability of inheritance increases with the senior partner's Diplomatic reputation.pngdiplomatic reputation and stability and decreases with the junior partner's number of provinces.

A personal union can end upon the death of the senior ruler when the junior partner has a negative opinion of its senior. If this occurs, the former senior partner will get a "Restoration of Union" casus belli on the former junior partner, allowing the union to be reinstated militarily.

Some nations can get a "Restoration of Union" CB against countries that they never had a union with in the first place, such as Austria, which can receive this casus belli against Bohemia and Hungary as a mission.

Only nations that have one of the Christian denominations as their state religion are able to form personal unions.

Colonial nation

Main article: Colonial nation

Subject colony icon.png Colonial nations represent the distant New World colonial territories of European powers. They will automatically form once five cored colonial provinces exist inside a single colonial region. Once formed, colonial nations will take control of any province that would otherwise be owned by their overlord in a given colonial region, even if the province is uncored or would otherwise cause extreme Overextension.pngoverextension.

Colonial nations pay a portion of their Income from vassals.pngtax income to their overlord, based on the tariff efficiency. Additionally, colonial nations transfer 50% of their Trade power.png trade power to the overlord.

When created, the colonial nation's flag is generated based on the mother country's flag and the colonial region the new Colonial Nation is located in. For example, a nation in the Mexico colonial region will have a yellow flag, while one in the Eastern North America colonial region will have a light-blue one.

Trade company

Main article: Trade company

A Subject tradecompany icon.png trade company is a collection of overseas provinces that exchanges tax and manpower for trade, maritime and production benefits.

A province in a trade company provides approximately half the Income.pngincome, no Manpower.pngmanpower, and no Sailors.pngsailors to the home country but produces double the Trade power.pngtrade power and adds 0.5 Naval forcelimit.png naval force limit. Additionally, the Local autonomy.png local autonomy floor is set to 0%, Goods produced.pnggoods produced remains unaffected by cultural intolerance, religious intolerance is ignored, and the province does not contribute to Religious unity.png religious unity.

Trade companies may be formed by nations that own at least one province in any of the 15 trade company regions scattered throughout Africa and Asia. They differ from colonial nations in the Americas and Australia in that they are not separate governments, as all territories remain part of the mother country. Provinces in trade company must belong to a territory - adding them to a state will automatically remove them from a trade company. Provinces can be added or removed from a trade company at any time. Only provinces on a different continent than the country's capital may be placed into trade companies.


Subject tributary icon.png Tributaries are a loose form of subject relationship available to nations in the Eastern religion group, as well as to steppe hordes and the Emperor of China regardless of religion. Tributaries retain full diplomatic independence and may start wars and have subjects of their own. The overlord receives a call to arms if the tributary is attacked (unless if by another tributary of the same overlord), but does not have to accept. Each year, the overlord may demand a tribute of Gold Icon.png money, Manpower.png manpower, or any of the 3 types of All power costs.png monarch points. The tribute is paid annually on January 2. Tribute type demand must be selected before January 1. The default tribute is Gold Icon.png money. If the tributary pays the tribute, trust increases slightly; if it refuses, trust falls significantly. AI always pays tribute when Liberty desire.png Liberty Desire is below 50% and refuses otherwise.

Monetary tribute is 12.5% of annual income, manpower tribute is 25% of annual gain, and monarch point tribute is 1 per 33 Development.png developments (rounded down) and capped at 12 for 400 or more development. If monetary tribute would be below 1 ducat, or monarch point would be below 1 point, they can't be selected. [1]

Either party may renounce the tributary status at will, unless they have a truce. The overlord gets a one-way five-year truce with the former tributary, but the former tributary may attack the overlord immediately. Tributaries who renounce their status lose -1 Icon stability.png stability; this can be circumvented by refusing tribute until the overlord breaks the agreement on their own.

The factors that influence an AI nation's desire to accept an Subject tributary icon.png Establish Tributary offer are:

Factor Effect
Attitude towards proposer Hostile attitude Hostile: -1000
 Outraged attitude Outraged: -1000
 Rivalry attitude Rivalry: -1000
 Threatened attitude Threatened: +100
Opinion towards proposer +1 per 4 positive points (rounded down)
 -1 per 4 negative points (rounded up)
Proposer's Diplomatic reputation.png diplomatic reputation +2 per positive point
 -2 per negative point
AI nation's government rank -20/-100 Kingdom/Empire
AI nation's Development.png development[2] -0.5 per Development.png development (rounded up)
Proposer economic base compared to target nation +90 to -90
Proposer military power compared to target nation +90 to -90
AI nation has subject of its own -1000
Are not neighbors -1000
Distance between borders -0.5 per distance between borders (defunct but still displayed)
Proposer is Celestial Empire or has horde government with rank Empire[3] +10


For a tributary overlord, sending manpower to tributary subjects at war can often be the cheapest way to decrease liberty desire and maintain the more value tribute income in the form of monarch powers. It can thus be helpful to set large tributary countries as "special interest" (right-click on country flag in provincial interface) and receive notification for wars by these tributaries.

For establishing tributary subject of AI nation, Threatened attitude threatened attitude gives the most significant +100. (Strangely, Friendly attitude friendly attitude does not give any modifier.) The attitude goes away at high opinion. Thus the optimal opinion with the threatened attitude is around 0. Player should avoid improving relation for too long in that case.


Main article: Japan#Daimyo & Shogunate

Daimyo are a unique form of vassal for the shogun of Flag of Japan Japan. They may ally with and fight other daimyo, but not foreign countries. They do not occupy a relation slot, and the shogun has several special vassal interactions for them. Note: outside nations can enforce peace on two warring daimyos without calling the shogun or its vassals to war, effectively providing a way for outside powers to get easy land on japan.


In previous versions of the game, technologically backward nations could be made protectorates, which exchanged a transfer of trade power and not being allowed other allies for protection from hostile nations and a discount on technology cost. They did not occupy a diplomatic relations slot. Protectorates were merged with regular vassals in patch 1.20.

Liberty desire.pngLiberty desire

All subject nations have a liberty desire between 0 and 100, indicating their wish for independence.

  • Below 50 a subject state is loyal: it pays taxes/tariffs to its overlord and takes an active part in all wars.
  • Above 50 liberty desire, a subject becomes disloyal, refusing to pay taxes while being unhelpful in wars by only defending its own territory. Disloyal subjects readily accept support for their independence from foreign nations and make alliances with each other, and may declare an independence war if they have sufficient strength. In rare cases, a disloyal subject may still have a Friendly attitude toward its overlord; this means it will not accept requests to support its independence or alliances from fellow subjects, but does not otherwise alter its behavior.
  • At 100 liberty desire, a state is rebellious, and will, at least in theory, declare its independence at the slightest opportunity.

Liberty desire depends on the sum of the following factors:

  • The relative army size of the subject compared to its overlord. There is +75 liberty desire for having 100% of the overlord's forces, scaling proportionately (e.g. +37.5 at 50%).
    • The combined strength of all vassals, marches, and client states is used for their liberty desire.
    • Personal union partners, daimyos, and colonial nations only consider their individual strengths.
    • Additionally, nations allied with or supporting the liberty of a subject nation will have their army strength added to that specific subject. Other subjects will not have their army strength increased, unless their independence is also supported.
  • A base modifier depending on type of subject: −25 for client states, −15 for March icon.pngmarches, +10 for Japanese daimyo; 0 for Vassal.pngvassals, Subject colony icon.pngcolonies and Personal union.pngpersonal union partners.
  • +0.25 per point of development for vassals, client states, and marches.
  • +5 for each level the overlord's Diplomatic tech.png diplomatic technology is behind the subject's.
  • −0.1 for each point of positive relations (max −20), +0.2 for each point of negative relations (max +40).
  • −5 for a Royalmarriage.png royal marriage.
  • −50 for historical Friendly attitudefriends.
  • +50 for historical Rivalry attituderivals.
  • +10 subject nation is a Government steppe horde.pngSteppe nomads.
  • −3 per point of diplomatic reputation.
  • ±0.4 per point of trust below/above 50 (min −20 at 100 trust, max +20 at 0 trust)
  • +1 per point of the overlord's Icon war exhaustion.pngwar exhaustion for colonial nations.
  • −50 if recently defeated in an independence war (decreasing over time).
  • +0.2 for colonies, per point of the colonial nation's Administrative efficiency.pngadministrative efficiency.
  • +1 for colonies, per point of Global tariffs.pngtariff rate.
  • −0.5 per Grant CoreClaim.png granted province development (sum decreasing over time by 0.1 per month).
  • −5 per each development point improved in subject's province (sum decreasing over time by 1 per year).
  • +1 per each Prestige.pngprestige below 0 (-50 Prestige.pngprestige equals +50 liberty desire)

Certain ideas reduce liberty desire in subjects:

Liberty desire in subjects Traditions Ideas Bonuses Policies
  • Influence idea 2: Additional Loyalist Recruitment
  • Ajami idea 7: Shahanshah
  • Berg idea 3: The United Duchies
  • Qara Qoyunlu 5: Freedom with Responsibility
  • Tyrone idea 1: Chief of Irish Kings
  • Plutocratic-Influence: Unified Army Command

Nobles agendas

These agenda can only be proposed by the Nobility.png Nobles estate.

Name Triggers Success Additional rewards
Hire a Military Advisor
  • No Does not already employ a Military Advisor
  • Advisor.png Has a Military Advisor
  • No Does not have negative monthly income
Fire our Military Advisor
  • Yes Has a Military Advisor
  • Advisor.png The Military Advisor has been fired.
Get Allies
  • No Does not have 3 allies
  • No Does not have 3 subjects
  • No is not at war
  • Yes Has at least 1 free relationship slot
  • Yes Has at least 2 allies.
Befriend rival of rival
  • Any rival country:
    • Is not at allied with ROOT
    • Has a -50 relation with ROOT
    • Has another rival that is not a rival of ROOT
  • Icon diplomacy relations.png Target has +100 relation
  • Gain Advisor Diplomat.png Master of Mint whose skill scales with your monthly income and who follows your religion. (50% cheaper to employ)
Restore legitimacy
  • Yes Is a monarchy
  • Yes Is not a regency
  • No Legitimacy is lower than 65
  • Legitimacy.png Has Legitimacy higher than 90
  • Gain Prestige.png +10 prestige
Improve Relations with X
  • Any known country:
    • Is not at rival of ROOT
    • Is not a subject of ROOT
    • Is not at war with Root
    • relation is not Icon diplomacy relations.png +50
    • relation is Icon diplomacy relations.png -50
    • Distance is less than 200
    • Root does not own a core
  • relation is Icon diplomacy relations.png +100
  • None
Get Aggresive Expansion down
  • No is not at war
  • Any known country:
    • Is in a coalition with target ROOT
  • Country is not in a coalition with target Root
  • Gain Diplomatic power.png +50
Condottieri against rival
  • Yes has Mare Nostrum
  • No is not at war
  • Any rival country
    • Is at war
  • Any country
    • Is at war with rival
    • Is not a rival
    • Has 5 cities
    • Closer than 200 distance
    • Has more than Icon diplomacy relations.png -50
    • Is not a tributairy
    • Army size and manpower less than half Root
  • Is renting Condottieri to target country
  • Gain Military power.png +50
Support independence of X)
  • Yes has "Conquest of Paradise" OR "El Dorado"
  • No is not at war
  • No is not a subject
  • Any rival country
    • Does not have truce with subject
    • Any subject country
      • Is not a daimyo
      • Is not a tributary
      • Has Liberty desire.png50% Liberty desire
      • Has more than Icon diplomacy relations.png -100
  • Is supporting the independence of target subject country
  • Gain Diplomatic power.png +50

Military focus

A nation can set its subject's military focus to any of the following, which will determine how they behave in wars. If the subject has more than 50% liberty desire, they will always behave as though set to passive.

Focus Behaviour
No focus The subject will decide its own strategies.
Supportive The subject will seek to attach to friendly armies.
Aggressive The subject will be aggressive towards enemies, seeking battles in enemy territory.
Focus Behaviour
Passive This will make the subject stay with armies in their own territory, and defend there. Unless escaping a larger threat.
Defensive This will make the subject defend its allies' territory. (Recommended for stronger subjects)
Siege This will make the subject use its armies to siege down hostile fortresses and not seek any battles.


  1. See in /Europa Universalis IV/common/defines.lua: variables with TRIBUTE_BASE_.
  2. See in /Europa Universalis IV/common/defines.lua: DIPLOMATIC_ACTION_TRIBUTARY_ACCEPTANCE_PER_DEVELOPMENT.
  3. See in /Europa Universalis IV/common/defines.lua: DIPLOMATIC_ACTION_TRIBUTARY_EMPIRE_FACTOR.

Ideas and Policies Idea groupsNational ideasPolicies
Ages and Institutions AgesInstitutions
Innovativeness and Technology InnovativenessTechnology