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A vassal is a semi-independent nation that owes allegiance to a country, often much more powerful than the vassal. The vassal offers regular financial tribute and military assistance, and in return receives protection.

Creating a vassal[edit]

There are several different ways to vassalize a nation. Countries can become vassals in the terms of a Peace Treaty, by diplomatic offer, or upon receiving autonomy from a larger country, either as a normal nation or as a Client state. The Emperor can also vassalize members of the Holy Roman Empire by passing the penultimate Imperial Reform.

Release a nation[edit]

A nation may release another nation whose lands it controls while it is at peace. This is something that may be desirable, for example, after gaining provinces in a peace that can't be cored or sold. The method of releasing a nation is as follows:

  1. Bring up the Diplomacy menu. If the player's country is not shown, click on View Own Country in the bottom right of the menu.
  2. In the bottom right hand corner of the menu that pops up, there is a button called Create Vassals.
  3. If the button is gray and not clickable then either there are no nations to release or the player is at war.
  4. Click the Create Vassals button and choose the nation to release as a vassal. Nations are eligible for release when the following conditions are satisfied:
    • Target nation does not currently exist
    • Releasing nation controls provinces that have the target nation's cores and a culture in the same group as their primary culture.

The released vassal will take the master country's religion, but only if the religion in the vassal's capital is of a different religious group. A same-religious-group capital will release as a vassal with its own capital's religion. The vassal may convert some provinces using its missionaries, leaving the suzerain's missionaries free. (false in 1.22)

Its tech group will be whatever that country had when it existed, although its initial tech levels will match its master, e.g. Creek will always release as New World Tech Group, Creek culture, its master's religion and its master's tech levels.

If the released nation's core provinces include the releasing country's capital, the capital will not be released, even if it is in the list of provinces to be released.

When releasing a nation into vassalage, the player may switch to playing as that vassal. When done in ironman mode, this will disable most achievements.

Kingdom of Jerusalem[edit]

A special case for releasing a country as a vassal is the Kingdom of Flag of Jerusalem Jerusalem, that can be released as a vassal through a decision by any Catholic ruler, except by The Knights or Cyprus who will instead remain in the control of the Kingdom. The releasing nation gains Prestige.png +25 prestige, and Jerusalem inherits the culture of the releasing nation.

Create a client state[edit]

Main article: Client state

A country with at least diplomatic technology 23 can create client states. They function identically to other vassals, but their provinces, government form, name, color and coat-of-arms can be customized by the player. They also have slightly less Liberty Desire than other vassals, and a unique group of Ideas shared by all client states. A country can have a maximum of 10 client states.

Create a march[edit]

Main article: March

A suzerain can also change a vassal (including a client state) into a march: special militaristic kind of vassal.

Force vassalization (military)[edit]

A nation can be force vassalized as part of a peace treaty. In the negotiations screen, there is an option for "Become Vassal" under the menu "Treaties" which should be the farthest right menu button on the screen. When force vassalizing a nation, the warscore needed is determined by the total development of all their provinces. The base warscore cost per point of development is 1.[1] Sometimes, the total development is too high to vassalize the target nation. The normal maximum is a total development of 100. However, certain missions/cb's can lower the warscore cost by a % (example: Subjugation reduces cost by 50%).

Generally only countries of 4 or fewer provinces, or poorer provinces can be vassalized via war. The maximum war score is 100% and a rich province typically costs about 25% war score. A good way to reduce a country's size is to force them to return cores and release countries, as these do not result in overextension or Aggressive Expansion for the annexing country. However, pagan countries can be annexed when fully occupied regardless of war score.

The benefits to the military victor of choosing vassalization instead of annexation are:

  • No Overextension penalty.
  • Using diplomatic points instead of administrative points to annex vassalized provinces.
  • The ability to feed a vassal, to conquer land without using one's own admin power, as well as to expand whilst having a lot of overextension.
  • less agressive expansion than simply conquering the provinces of the country.

The downsides to the military victor of choosing vassalization instead of annexation are:

  • The vassal occupies a diplomatic relation slot, reducing the number of allies possible (but vassals are more dependable than allies).
  • The direct benefits of those provinces to the overlord are smaller than if they belonged to the overlord (less tax, production, forcelimits, trade power, and the overlord can't build buildings). (However, the overlord and vassal combined are stronger than either one alone.)
  • Longer time until the land is part of the victor's country. There is a waiting period of 10 years in addition to the time that it takes to diplo-annex the vassal.
  • Once annexed the Local Autonomy of every province will be raised to 60%, instead of 50% if taken in war without a claim
  • Once annexed, the country gains a -3 malus to its diplomatic reputation. This matters in regards to being elected as the emperor, diplo-vassalizing countries and diplo-annexing ones, as well as a host of other diplomatic actions. Without help from advisors, ideas, or events, annexing another vassal will be very slow or impossible until this malus expires.

Offer vassalization (diplomatic)[edit]

The requirements for offering diplomatic vassalization are as follows:

  1. Must have at least +190Friendly attitude relations with the target country.
  2. Must be Alliance.pngallied to the target country.
  3. Target country must be at peace.
  4. The difference in Technology cost.pngtechnology cost between the vassalizer and the target country must be less than 50% (otherwise the target can only be made a Icon protectorate.pngprotectorate). After patch 18 the difference shouldnt be higher then 1 accepted institution.
  5. Target country must have at most 100 Development.pngdevelopment

Willingness to accept vassalization is shown in the tooltip for the check-mark in the "offer vassalization" button.

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

Factor Effect
Attitude towards proposer Alliance.png Ally: +10
 Friendly attitude Friendly: +10
 Threatened attitude Threatened: +10
 Neutral attitude Neutral: -20
 Hostile attitude Hostile: -100
 Outraged attitude Outraged: -100
We have a Royalmarriage.pngroyal marriage +10
Trust Scales linearly between the following points:
 +10 at 100 trust
 0 at 50 trust
 -40 at 30 trust
 -2000 at <30 trust
Proposer's Diplomatic reputation.pngdiplomatic reputation +3 per positive point
 -3 per negative point
Difference in government rank +10 per difference in rank
Nation has a religion not in the same religious group -20
Nation has a different religion within the same religious group -10
Nation is a Government republic.pngmerchant republic -30
Proposer economic base compared to target nation +30 to -90
Proposer military power compared to target nation +20 to -40
Proposer is a Government republic.pngmerchant republic -10
Nation is member of the Imperial authority.pngempire -25 if proposer is also a member
 -75 if proposer is not a member
Nation is an elector -1000
Nation has subjects of their own -1000
Nation is Flag of The Papal State The Papal State/the Pope -1000
Nation has more than 100 total Development.pngdevelopment -1000
Nation is not a strategic interest -1000
Distance between borders -0.5 per distance between borders

†: Distance between borders can only be seen in debug mode.

‡: Determined by:

\text{relative economic base} = 60\,\cdot\,\frac{\text{base tax} + \text{base production} + \text{current vassal base tax}} {( \text{target base tax} + \text{target base production} + \text{target base manpower} )^2}\,-\,90

Where base tax and production are the total province base tax and production of the country without any buildings or modifiers. Note that these provinces have to be states, or they will not count. The base tax of all current vassals also adds to the economic base of the nation offering vassalization.

Break vassalization[edit]

  • Through a peace deal: when suzerain loses a war.
  • Through diplomacy: a suzerain can chose to release its vassal for a cost of -25 prestige and -200 vassal's opinion modifier.

Benefits of vassals[edit]

Vassals are essentially puppets of their suzerain, or overlord country. They cannot declare war or enter royal marriages, except with their overlord. They always join their suzerain's wars, and cannot negotiate separate peace treaties.

The suzerain also receives military access and the ability to dock its boats in the vassal's ports, but not fleet basing rights. If the vassal is an elector in the Holy Roman Empire, its suzerain gets a +50 point bonus to the vassal's electoral vote opinion and a -50 point malus (stacking for each vassal) to the opinions of non-controlled electors.

Vassals may try to break free by declaring war on their overlord. They may also ask other nations to support their independence. Nations supporting independence are automatically called into the independence war, and act as temporary allies for the duration of the war. Other countries may offer support for independence without being asked, although vassals that like their overlord will never accept.

After ten years vassals can be annexed by their suzerain, which gets cores on all provinces that the vassal considers cores. This makes vassalization a good way to expand without spending administrative points, or in some cases even without having to wage war.

Income from vassals[edit]

Vassals have to pay a part of their tax income to the suzerain. This part is determined by the ‘vassals tax efficiency’ of the overlord, which is the sum of all ‘income from vassals’ modifiers. The base value for the all countries is 10%.[2] A overlord can increase its ‘vassals tax efficiency’ by the following:

Income from vassals.png Conditions
+33% as iqta
+25% as elective monarchy or feudal monarchy
+10/20/30% as tribal kingdom (depending on government rank)
+5% with Parliament.png parliament and “Harmonization of State Laws” or “Create Offices for Vassal Nobles” as active issue
–5 - +5% depending on Legitimacy.png legitimacy (0-100)

Ideas and policies:

Income from vassals.png Traditions Ideas Bonuses Policies
  • Offensive-Administration: Vassal Taxation Policy
  • Kanem Bornuan traditions
  • Mesoamerican traditions
  • Timurid traditions
  • Influence idea 1: Tribute System
  • Ashikaga idea 7: Reform the Shogun - Shogu System
  • Bosnian idea 5: Land of Princes
  • Ayutthayan ambition
  • Influence-Economic: Vassal Obligations Act
  • Influence-Expansion: Overseas Dominions
  • Influence-Quality: The Integrated Administration Act
  • Georgian idea 4: Georgian Protectorates
  • Malian idea 1: Restore Malian Suzerainty
  • Lunda ambition
  • Zambezi ambition


Income from vassals.png Event modifier Trigger Duration
+25% Firm Hand Influence ideas event: “A Firm Hand for 10 years.
+10% Vassals Feel Safe Influence ideas event: “Vassals Feel Safe for 10 years.
−5% Vassals are unwilling to pay scutage Subject interaction events: “War Never Changes for 5 years.

The overlord can increase the paid vassals tax by +50% if he asks for scutage in exchange for the renunciation of military support from the vassal.

Vassal force limit contribution[edit]

Vassals increase the suzerain's land force limit by 1[3] and marches by 2[4], but not the naval force limit. This contribution can be increased by the following.

Ideas and policies:

Vassal forcelimit bonus.png Traditions Ideas Bonuses Policies
  • Influence idea 7: Marcher Lords
  • Ashikaga idea 7: Reform the Shogun - Shogu System
  • Bosnian idea 5: Land of Princes
  • Influence-Aristocratic: Autonomous Estates
  • Influence-Economic: Vassal Obligations Act
  • Influence-Offensive: Unified Army Command

Decisions and events:

Vassal forcelimit bonus.png Event modifier Trigger Duration
+100% Firm Hand Influence ideas event: “A Firm Hand for 10 years.

Liberty desire[edit]

Main article: Subject nation#Liberty desire

Vassals have liberty desire (introduced with patch 1.10) like the other subject nations. A liberty desire less than 50% will remain in the Loyal attitude 'loyal' attitude, while vassals with a liberty desire above 50% will become Disloyal attitude 'disloyal'.

Nations who are historical rivals will have a base liberty desire of 50% and as such make poor vassals since to diplo-annex them there needs to be less than 50% liberty desire.

Disloyal vassals may:

  • Refuse to send troops to a war waged by the liege.
  • Seek independence support and accept independence support from other countries.
  • Forge alliances with other disloyal vassals.
  • Declare a war of independence (which they will once they believe they have a chance based on the relative military powers of them and their allies versus their liege).

Many factors affect liberty desire, including relative military strength, relations, royal marriages and trust.

Because vassals taken from wars have poor opinions and distrust of their new liege, it is important to raise the vassal's opinion as much as possible before the truce from the war expires. When suing for peace, increasing the warscore cost of the demands will also increase the truce period, granting more time to improve vassal's opinions, build trust through wars, and allow bad opinion modifiers to decay.

Subject interaction[edit]

Main article: Subject_nation#Subject_interactions

As of 1.12, it is now possible to interact with a vassal. This is done through the Subject Interaction section of the Subject Menu.


A vassal or client state can be diplomatically annexed by its overlord through the Annex vassal option. Annexation occupies a Diplomat.pngdiplomat until complete, and results in direct control of the former subject's territory and military.

The requirements for initiating diplomatic annexation are:

  1. The subject's vassalage has lasted at least 10 years. The vassalization date can be found in the vassal's diplomacy screen on the tooltip for the vassalage icon Vassalage.png.
  2. Vassal opinion of overlord is at least 190.
  3. Liberty desire is less than 50%.
  4. Vassal is at peace.
  5. Vassal has control of its Capital.pngcapital.

Annexation progress of vassals appears in the diplomacy interface as a small vertical progress bar next to the vassalage icon Vassalage.png. If the annexation process is cancelled before completion, all progress is lost, including the invested Diplomatic power.pngdiplomatic power.

Diplomatic annexation will be paused if:


The total cost of annexation is 8 Diplomatic power.png diplomatic power per Development.png development of the vassal. This cost is increased by the Hostile core-creation cost on us.pnghostile core-creation cost modifiers of the vassal's corresponding provinces, and decreased by Administrative efficiency.pngadministrative efficiency and modifiers that reduce Diplomatic annexation costannexation cost. These modifiers are displayed below:

Diplomatic annexation cost Traditions Ideas Bonuses Policies
  • Influence idea 3: Integrated Elites
  • Influence-Administrative: Vassal Integration Act
  • Austrian idea 1: Imperial Ambition
  • Zambezi idea 6: Wealth of the Shire Valley
  • Naxian ambition
  • Plutocratic-Influence: Full Sovereignty Act

Note that the diplomatic annexation cost can change during annexation, meaning that it may be worth only buying modifiers once the full annexation cost (post-modifier) has nearly been paid.

The full formula for diplomatic annexation cost is:

\text{dip point cost} = \text{floor}\left( \sum_\text{per province}\left[ 8 \cdot \text{development} \cdot (1 - \text{administrative efficiency}) \cdot \left(1 + \sum\text{annexation cost modifiers}\right) \cdot \left(1 + \sum\text{local coring cost modifiers}\right) \right] \right)

Note that even with a −100% modifier to annexation cost, annexation will still cost a minimum of 12.5% of the full annexation cost.

Speed of annexation[edit]

The overlord invests diplomatic power into the annexation process each month at the following rate:

If the total is 0 or negative, annexation will pause, but not reverse.


Annexation is completed once the required diplomatic monarch points are spent, and results in the following effects:

  • +5 prestige.
  • An event gives the "Annexed Vassals" national modifier for 10 years giving -3 Diplomatic reputation.png diplomatic reputation.
  • -30 relations with other vassals. Stacks. Does not apply to marches.
  • -25 relations with other HRE members, if the vassal was in the Holy Roman Empire.
  • Control of all the vassal's provinces, army, and navy. This may put the overlord over its force limit.
  • Cores on all the vassal's core provinces.
  • 60% Local autonomy.png local autonomy in all new cores (or their previous autonomy level, if above), and 0 if the overlord already had a core.


For the Glory icon
Diplo-annex a vassal.

Diplomatic annexation strategy[edit]

Due to the administrative point cost and time of coring conquered provinces, especially for large countries, diplomatic annexation is an interesting alternative to conquer large swathes of the world: when a vassal is annexed, all of the vassal's core provinces become cores of the annexing country. Annexation also doesn't incur aggressive expansion relations penalties and no separatism is incurred if Separatist Rebels have not taken control of any provinces since the initial annexation. The diplomatic power is also expended over time and there is no penalty akin to overextension for taking a long time while annexing.


  • Better Relations Over Time is the most important bonus, as it makes Aggressive Expansion decay faster. Hiring a Diplomat increases this modifier.
  • Static modifiers include:
    • Royal Marriage +25
    • Alliance +50
    • Enemy of my Enemy (have the same rival as them) stacking 1/year up to +20
    • Same religion +10
    • Guarantee by promising to defend against aggressors +10
    • Military Access by giving target nation military access +10
    • Imperial Grace +40 (the emperor of the Holy Roman Empire can spend imperial authority to increase relations with a country).
  • Decaying modifiers include:
    • Gift by giving money to the target country +1 up to +25 (60 months)
    • Honored Alliance by responding to a request for military aid +10 (decays/year)
    • Fought to the End by not negotiating a separate peace in an alliance war +20 (decays/year).
    • Defending the vassal territory from an army +10 (decays/year)
    • Liberating vassal territory from an occupation +25 (decays/year). Both defending and liberating provinces work against rebels.
    • Giving war subsidies, up to +15. Once cancelled, relations boon is gone.

Choosing a vassal[edit]

A good candidate for diplomatic annexation has the following:

  • Lots of unowned cores or claims: wage war with other nations and take the provinces cored or claimed by the vassal so they can core the land instead of you. The "Grant Province" option should be used from 1.14 onwards, as it reduces the liberty desire of the vassal by half of the total development granted, easily keeping it in line, provided granting the province does not increase your subject's total development over 100.
  • Strong military ideas or economic ideas - large vassals can contribute 20,000+ men to wars, sieging down forts on a different front, cleaning up unfortified provinces that haven't been occupied and sometimes even winning battles on their own.
  • Not a merchant republic; they have a malus for accepting vassalization.
  • No Hostile core creation modifier - these are applied to all cored provinces, including newly cored ones "fed" to the vassal, making those provinces even more expensive to annex than they normally would have been. In particular, North African and Caucasian nations tend to have these modifiers in their traditions.
  • Ability to deal with unrest without overlord army help. While you can keep your armies around to patrol for rebels in vassal lands, it is better to look for a vassal that has unrest reduction, tolerance or missionary strength in its National Idea set. Ideally the vassal will be the same religion as the overlord but it is not necessary.
  • Same culture/religion as overlord - each will increase the diplomatic power per month spent on annexation. If Diplomatic Reputation is low then this can make a huge difference in annexation speed.

Feeding a vassal[edit]

It is sometimes advantageous to transfer provinces to a vassal. This is called "feeding" the vassal. Because each vassal takes up a diplomatic relations slot, as well as a Diplomat during the actual annexation process, it can be a good idea to "feed" vassals provinces rather than take on additional vassals - each vassal annexed also makes it more difficult to annex subsequent vassals with a stacking -30 hit to relations that can make it impossible to get older vassals above 190 relations along with a -3 penalty to diplomatic reputation for 10 years, reducing the speed at which vassals can be annexed in that time. However, the more provinces the vassal has, the higher its overall development, increasing the diplomatic power required to annex it. Large vassals can take thousands of diplomatic power and decades to annex, even with discounts from Influence ideas and Administrative efficiency. It is recommended to try and only annex vassals when taking Influence ideas as the cost will be 25% less; for a bigger discount, adopt the Vassal-Integration Act policy (requires Administrative Ideas completed in addition to Influence Ideas).

Since 1.14 the best way to feed a vassal is to annex territory directly and grant the provinces to the vassal through the subject interaction menu. This will reduce the vassal's liberty desire by half of the total development granted to it, easily offsetting the increase in liberty desire that vassals get from becoming more powerful and can even negate the +25%/+50% liberty desire taken on by vassals who have more than 100 or 300 development, respectively - feeding a vassal even 200 development worth of land will reduce its liberty desire by 100%. Vassals will not accept a province if it will increase their Overextension to 100% or more, and by annexing the land directly the overlord might have to suffer more Aggressive Expansion and pay diplomatic power for the provinces, if the provinces being taken were not included in the war goal.

The advantages of vassal feeding are primarily in not having to deal with rebels as much (as the AI will often use its military power for Harsh Treatment, saving you the expense) and saving Administrative Power in favour of expending Diplomatic Power; Administrative Technology is almost always more important than Diplomatic Technology as it allows you to unlock new idea groups. From patch 1.16, care must be taken to balance vassal feeding with direct expansion as falling too far behind in diplomatic tech relative to administrative and military tech will increase corruption.

Returning cores[edit]

The suzerain can give provinces to a vassal by forcing a defeated country to return the vassal's cores in a peace deal. This is less expensive in terms of Aggressive Expansion than taking provinces directly, but still costs the same diplomatic monarch points. Since these provinces are the vassal's cores, they will not overextend the vassal. Returning provinces gives a large boost to the receiving country's opinion of the military victor (+40 per province up to 200 total, decay at 1 per year).

Alternatively, a vassal may independently occupy an enemy province where it has a core. A province sieged by a vassal will be occupied by their suzerain, but an exception is when the vassal has a core in the province and is the siege leader. The suzerain can also transfer occupation to their vassal whenever needed.

Once a province is occupied by the vassal, the suzerain war leader can demand the enemy to directly cede the province to the vassal. If this happens, the vassal will use their own diplomatic monarch points though their overlord will still take the Aggressive Expansion for the province. This also gives an opinion boost, but less than returning a core with the suzerain's diplomatic monarch points.

Selling provinces[edit]

Selling provinces will not work if the annexation process has been started. Countries who are already vassals will only buy provinces that are either cores, claims, an accepted culture or formerly owned territory of the vassal. The province history button can confirm if a territory is formerly owned if there is no longer a claim/core there. Also the province to be sold needs to be within coring range.

It is much easier to sell provinces to countries that aren't yet vassalised, however care must be taken to make sure that after selling the province the country doesn't become ineligible to become a vassal (either diplomatically or militarily due to tax base).


Since the cost of annexation can change during annexation, it may be worth only buying modifiers once the full annexation cost (post-modifier) has nearly been paid, especially if the modifier is a policy (i.e. the cost is increased for every month over 10 years for which it is active).

Consider timing annexations so that they finish within six months of one another: since an event such as that giving the Annexed Vassals modifier can be postponed for up to six months, the player can, for this time, avoid the hit to Diplomatic reputation.pngdiplomatic reputation, and can annex vassals at full speed without waiting 10 years between annexations. Since the -3 Diplomatic reputation.pngdiplomatic reputation from the Annexed Vassals modifier does not stack, you will also avoid both long periods with the penalty and short periods with an extreme penalty.


  1. See in /Europa Universalis IV/common/defines.lua PEACE_COST_BECOME_VASSAL = 1
  2. See in /Europa Universalis IV/common/static_modifiers/00_static_modifiers.txt (Static_modifiers#Base_values).
  3. See in /Europa Universalis IV/common/static_modifiers/00_static_modifiers.txt (Static modifiers#Vassal subject).
  4. See in /Europa Universalis IV/common/static_modifiers/00_static_modifiers.txt (Static modifiers#March subject).
Subject nations Client stateColonial nationMarchPersonal unionTrade companyTributaryVassal
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