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

Creating a vassal[edit | edit source]

There are several different ways to vassalize a nation. Countries can be force vassalized in a Peace Treaty or can agree to vassalization via a diplomatic offer. They can also receive autonomy from a larger country, either as a normal nation or as a client state. The Holy Roman Emperor can also vassalize members of the Holy Roman Empire by passing the penultimate Imperial Reform, "Revoke The Privilegia".

Releasing a nation[edit | edit source]

A nation at peace may release another nation whose lands it controls. This can help after gaining provinces in a peace deal that can't be cored or sold, drive overextension too high, or are extremely rebellious. One can also release a vassal in order to reconquer its core provinces in future wars for less aggressive expansion and no administrative power cost for either country. 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:
    • The country is at peace
    • Target nation does not currently exist
    • Releasing nation owns and controls provinces that have the target nation's cores and a culture in the same group as their primary culture.

For example, Iraq has a core on Hisn Kayfa. However, this province's culture is Kurdish, which is in the Iranian culture group; Iraq's historical culture is Mashriqi, which is in the Levantine culture group. As such, it is not possible to release Iraq from Hisn Kayfa. You'll have to conquer a province with both an Iraqi core and a Levantine culture.

Whatever religion is the largest in all of the new vassal's cores everywhere in the world (even if currently not owned by the nation) in terms of development will become the vassal's state religion (cores belonging to its original religion apparently count double); the number of provinces following any given religion is not the determining factor. If a same-religion vassal is necessary, converting the future vassal's richer provinces before releasing the vassal will ensure the vassal's adherence to the true faith.

The new country will maintain its default assigned tech group but will start with all the technologies its master possesses. The Creek, for example, will always release as North American tech group country with Creek culture equal to its master in technology.

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.

Create a march[edit | edit source]

Main article: March

A suzerain can also change a vassal (including a client state) into a march, which is a special militaristic kind of vassal. Marches gain bonuses to their military power but cannot be diplomatically annexed and do not pay taxes to their overlord. The overlord can revoke march status but will suffer a -1 Stability.png stability hit and a -50 penalty to relations with the former march. As long as the march's development is less than 25% of its overlord's, it receives the following bonuses:

National manpower modifier.png +25% National manpower modifier
Land force limit modifier.png +30% Land force limit modifier
Naval force limit modifier.png +30% Naval force limit modifier
Fort defense.png +20% Fort defense
Fort maintenance.png −20% Fort maintenance
Manpower recovery speed.png +20% Manpower recovery speed
Land maintenance modifier.png −20% Land maintenance modifier
Naval maintenance modifier.png −20% Naval maintenance modifier

Force vassalization (military)[edit | edit source]

A nation can be forcibly vassalized as part of a peace treaty (option in the Treaties menu of the negotiation screen). The total warscore cost for force vassalization is 1 warscore per 1 development plus 5 warscore for each province (plus roughly 25% of the capital province development, plus a value for local trade power), so you can only vassalize countries with typically at most 70 development and 3 to 4 provinces without cost reductions via absolutism or the rare Subjugation casus belli (available through some missions and events). To see the target cost select a province and hover your mouse over the "Province War Score Cost", a crossed shield and star icon, it will also show you the total force vassalization cost.

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

  • No Overextension penalty or separatist unrest (usually +15, decaying by only 0.5 per year).
  • Using diplomatic points instead of administrative points to annex vassalized provinces.
  • The ability to feed a vassal provinces in peace deals, gaining land without using one's own administrative power or becoming overextended. This is especially useful for countries that have many foreign cores, as conquering them on the vassal's behalf incurs less aggressive expansion, costs less manpower with the reconquest CB, and results in no separatist unrest or autonomy.
  • Aggressive expansion penalty reduced by a third.
  • The vassal will manage its own armies in war, which is less micromanagement for a player ruling a massive empire.

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).
  • Little monetary benefit to the overlord. However, if a vassal has provinces in states, is paying a high vassal tax and possibly transferring trade power, the difference to owning the provinces yourself as mere territories is not huge.
  • Longer time until the land is part of the victor's country. There is a waiting period of ten years in addition to the time that it takes to diplomatically 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 for ten years. This matters in regards to being elected as the Holy Roman Emperor, diplo-vassalizing and diplo-annexing countries, and many other diplomatic actions as well. Without help from advisors, ideas, or events, annexing another vassal will be very slow or impossible until this malus expires, so you should ideally time multiple annexations to complete at once.

Newly force-vassalized countries will receive a −100 opinion malus to relations with their overlord, which will decay at a rate of 2 per year. It is often a good idea to immediately begin improving relations with the new vassal to prevent disloyalty. The vassal cannot seek support for independence until the truce expires.

Be careful if the country you are vassalizing is currently involved in a different war: In all other wars in which they are the war leader, whether on the attacking or the defending side, you will take their place! (If they are merely involved as an ally, they will sign an automatic white peace instead.) If your potential new vassal is leading the attack or defense in a difficult war, or leading a war against an ally of yours, you should probably wait for peace or just annex whatever you can directly.

However, you can also use this mechanism to your benefit: Vassalize a small neighbor while they are also defending against a large neighbor, and, most likely, you will be able to call AI allies to support you, while the AI attacker will be unable to do so. This is a good strategy when playing small-to-medium-sized nations with dangerous neighbors, e.g. Novgorod vs. Muscovy vassalizing Tver or Byzantium vs. Ottomans vassalizing Albania.

Offer vassalization (diplomatic)[edit | edit source]

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% After patch 18 the difference shouldn’t be higher than 1 accepted institution.
  5. Target country must have at most 100 Development.pngdevelopment
  6. Must not own cores of the target country.

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:

Vassalization acceptance Traditions Ideas Bonuses Policies
  • Espionage idea 7: Blackmailing
  • Zulu idea 7: Conquest through Patronage
Factor Effect
Attitude towards proposer Alliance.png Ally: +10
 Friendly attitude Friendly: +10
 Threatened attitude Threatened: +10
 Neutral attitude Neutral: −20
 Hostile attitude Hostile: −1000
 Outraged attitude Outraged: −1000
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 for each higher rank
−30 for each lower rank
Nation's government rank Kingdom rank kingdom: −10
Empire rank empire: −20
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[diplomatic vassalization 1]
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
Proposer owns target nation's core provinces −1000
Distance between borders −0.5 per distance between borders[diplomatic vassalization 2]
Flag of Austria Austria mission: Shift the Balance +25 for Time Icon.png30 years
Flag of Savoy Savoy mission: Push on Tuscany +30 for Time Icon.png30 years
Flag of Songhai Songhai mission: Protect our Legacy +15 for Time Icon.png25 years
  1. Determined by:
    The target countries vassals don't matter in practice, because a country with subjects can't be vassalized.
    The minimum value is −90 and the maximum +30. Only vassals(and daimyos) matter for the formula. The development of marches, junior partners, colonial nations and tributaries is not taken into account. The autonomy modified development of the players country is displayed in the tooltip of the presence bar of an institution in the technology tab. Reworking the formula it be be simpler to use this formula to determine "the proposer's required size = 3*((target's dev+10)/2)^2"
  2. Distance between borders can only be seen in debug mode.

Break vassalization[edit | edit source]

  • Through a peace deal: when suzerain loses a war.
  • Through diplomacy: a suzerain can choose to release its vassal for a cost of -25 prestige and -200 vassal's opinion modifier. However, if the vassal has over 50% liberty desire, the relation penalty won't happen.

Benefits of vassals[edit | edit source]

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 fleets 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, being complete countries in their own right, have their own armies, navies, manpower, and envoys. The armed forces of a vassal and overlord are stronger than the overlord's would be alone if those provinces were annexed, and often the vassal's religious and cultural tolerance enables them to exploit their land more efficiently than the overlord could. The additional missionaries can make religious conversion faster, and their merchants can help steer trade in the correct direction.

Vassals may try to break free by declaring war on their overlord. With Conquest of Paradise.pngEl Dorado.png DLC, 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 | edit source]

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%.[1] A overlord can increase its Income from vassals.png Income from vassals modifier 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)
+10Great project level icon tier 2.png/20%Great project level icon tier 3.png holding Great project versailles.pngVersailles while culture in province is in French group and accepted by owner (only with Leviathan.png)
+10%Great project level icon tier 1.png holding Great project alhambra.pngAlhambra while religion in province is in either Christian or Muslim group and same as owner (only with Leviathan.png)
+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-Administrative: Vassal Taxation Policy
  • Tongan idea 2: Pulotu's Creation
  • Kanem Bornuan traditions
  • Mesoamerican traditions
  • Influence idea 1: Tribute System
  • Ashikaga idea 7: Reform the Shogun - Shugo System
  • Bosnian idea 5: Land of Princes
  • Herzegovinian idea 5: Land of Princes
  • Jolof idea 3: The Tribute of the Five Kingdoms
  • Malaccan idea 1: Vassal Princes
  • Goslar ambition
  • Influence-Economic: Vassal Obligations Act
  • Influence-Expansion: Overseas Dominions
  • Influence-Quality: The Integrated Administration Act
  • Lusatian traditions
  • Ayutthayan idea 1: White Elephant
  • Malian idea 1: Restore Malian Suzerainty
  • Zimbabwe idea 6: Tributary System
  • 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.

Vassal specific:

Income from vassals.png Conditions
+50% If Scutage is enabled for that vassal in Subject Interactions

Vassal force limit contribution[edit | edit source]

Vassals increase the suzerain's land force limit by 1[2] and additionally 10% of the vassal's force limit[3] and marches by 1[4] and additionally 20% of the march's force limit[3], but not the suzerain's naval force limit. This contribution can be increased by the following.

Ideas and policies:

Vassal force limit contribution.png Traditions Ideas Bonuses Policies
  • Influence idea 7: Marcher Lords
  • Andalusian idea 2: Taifa Administration
  • Ashikaga idea 7: Reform the Shogun - Shugo System
  • Bosnian idea 5: Land of Princes
  • Herzegovinian idea 5: Land of Princes
  • Majapahit idea 1: Nusantara Tributaries
  • Horde-Influence: Kharash
  • Influence-Aristocratic: Autonomous Estates
  • Influence-Economic: Vassal Obligations Act
  • Plutocratic-Influence: Unified Army Command
  • Tongan idea 2: Pulotu's Creation

Decisions and events:

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

Liberty desire[edit | edit source]

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 subjects.
  • 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).
  • Prevent their own annexation, or pause it if annexation has started.

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

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 | edit source]

Main article: Subject_nation#Subject_interactions

Interactions with vassals are done through the Subject Interaction section of the Subject Menu.

Annexation[edit | edit source]

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.
  6. Vassal has at least one core province that can be cored.

Annexation progress of vassals appears in the diplomacy interface as a horizontal 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 vassal's Liberty desire.png liberty desire is greater than 50%;
  • the vassal does not have control of its Capital.png capital; or
  • the vassal is at war and any of its provinces are occupied by rebels or an enemy nation.

Cost[edit | edit source]

The full formula for diplomatic annexation cost is:

Development of provinces the overlord already has cores on is not included. The cost reduction from administrative efficiency is capped at 90% and the final cost per province can not go below 0.1 dip points per development(or 1.25% of the normal cost). The final cost for the whole country is rounded, so it can be 0 in extreme cases.

The base annexation cost is 8 Diplomatic power.png diplomatic power per Development.png development of the vassal, excluding any provinces the overlord has cores on. The cost in diplomatic power is increased by the local coring cost modifier which refers to the Hostile core-creation cost on us.pnghostile core-creation cost of the vassal. Having claims or permanent claims on some provinces of the vassal does not change the integration cost. This cost is decreased by Administrative efficiency.pngadministrative efficiency, All power costs.png all power cost modifiers and Diplomatic annexation costdiplomatic annexation cost modifiers. These modifiers are displayed below:

Diplomatic annexation cost Traditions Ideas Bonuses Policies
  • Influence idea 3: Integrated Elites
  • Siamese idea 5: Consolidation of the State
  • Influence-Administrative: Vassal Integration Act
  • Austrian idea 1: Imperial Ambition
  • British idea 1: The Acts of Union
  • Chagatai idea 3: Sons of Chagatai Khan
  • Cilli idea 1: Dynastic Marriages
  • Clevian idea 5: United Duchies
  • Gelre idea 7: Land Negotiations
  • LPC idea 4: Reciprocal Guarantee of Two Nations
  • Manx idea 7: The Act of Revestment
  • Zambezi idea 6: Wealth of the Shire Valley
  • Ayutthayan ambition
  • Ligori ambition
  • Majapahit ambition
  • Naxian ambition
  • Danish idea 1: The Kalmar Union

Further modifiers:

Type Diplomatic annexation cost
permanent modifier “King of Kings” from the Flag of Provence Provence Mission.png mission King of Kings −20%
with Parliament.png parliament and “Harmonization of State Laws” or “Create Offices for Vassal Nobles” as active issue −15%
permanent modifier “Bohemian Commonwealth” from the Flag of Bohemia Bohemia Mission.png mission Bohemian Commonwealth −15%
permanent modifier “Lord of Austria” from the Flag of Hungary Hungary Mission.png mission The Duchy of Austria −10%
Papal Legate modifier for 20 years −10%
permanent modifier “Unity of Italy” from the Mission.png mission “Union with Naples” which is available for Flag of Savoy Savoy and Flag of Sardinia-Piedmont Sardinia-Piedmont −10%
with noble privilege Nobility Integration Policy −5%

Speed of annexation[edit | edit source]

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

If the total balance of diplomatic power is 0 or negative (hence the balance cannot cover the monthly rate), annexation will pause, but not reverse

Note that if acquiring multiple subjects concurrently, this monthly rate as above will apply to each subject independently (modified for the culture and religion of each), even if it results in a monthly deficit; as long as there is still a positive diplomatic power balance to cover the monthly deficits as per the rule above. If not, progress will pause.

Effects[edit | edit source]

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 Diplomatic reputation.png −3 diplomatic reputation. (While the penalty does not stack, the duration of the penalty does so annexing 3 vassals will result in a 30 years penalty). You can avoid getting this penalty by granting a particular estate privilege to your countries version of the nobility.
  • −30 relations with other vassals. Does not apply to marches. Will vanish completely after 20 years if no new stacks are added, regardless of current amount. (Stacks. -200 limit)
  • −25 relations with other HRE members, if the vassal was in the Holy Roman Empire. (Stacks)
  • 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.

Diplomatic annexation strategy[edit | edit source]

Strategy The below is one of many player suggested strategies for Vassal. Bear in mind, due to the dynamic nature of the game, it may unfold differently for other players.

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.

Preparations[edit | edit source]

  • Improve Relations is the most important bonus, as it makes Aggressive Expansion decay faster. Hiring a Diplomat advisor 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
    • Transfer Trade Power by asking target nation to transfer trade power to your nation +10
    • Imperial Grace +40 (the emperor of the Holy Roman Empire can spend imperial authority to increase relations with a country).
    • Great Power influence: +25 as long as influence is active (10 years unless renewed)
  • 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 | edit source]

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.
    • If Muslim with the Cradle of Civilization.png Cradle of Civilization DLC, try to pick one from a different school so you can freely invite their scholars.
  • National Ideas which increase a vassal's force limit in turn increase your own force limit due to the percentage for the vassal's force limit being added to your own. Likewise, vassals which take Offensive and Quantity ideas further increase this.

Feeding a vassal[edit | edit source]

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).

The best way to feed a vassal is to annex territory directly and grant the provinces to the vassal through the subject interaction menu (requires Common Sense.png Common Sense). This will reduce the vassal's liberty desire by half of the total development granted to it, temporarily offsetting the increase in liberty desire that vassals get from becoming more powerful and gaining more development - feeding a vassal even 200 development worth of land will reduce its liberty desire by 100%(but increase it again by 50% because of the increased development). 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 | edit source]

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.

Beware that the Administrative Efficiency Administrative efficiency.png used to compute the province war score cost is the one of the country who receives it. If you have a better Administrative Efficiency than your vassal, you will have to pay more war score cost to give him directly those provinces (via "Cede province" or "Return core") than taking them for you directly and ceding them to the vassal in peacetime (via the option in the Subject Interaction menu (available with the Common Sense.png Common Sense DLC)). But as previously mentioned, the first option will give less Aggressive Expansion, and give an opinion bonus, whereas the second one will give more AE and also a reduction in Liberty Desire Liberty desire.png for the concerned subject (more than you get from the opinion boost in the first option), which stacks (contrary to opinion, capped at 200).

Selling provinces[edit | edit source]

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).

Annexing the vassal[edit | edit source]

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 four months of one another: since an event such as that giving the Annexed Vassals modifier can be postponed for up to four 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 Diplomatic reputation.png −3 diplomatic reputation from the Annexed Vassals modifier does not stack, you will avoid long periods with the penalty.

Achievements[edit | edit source]

For the Glory icon
For the Glory
Diplo-annex a vassal.

Footnotes[edit | edit source]

  1. See in /Europa Universalis IV/common/static_modifiers/00_static_modifiers.txt (Static_modifiers#Base_values).
  2. See in /Europa Universalis IV/common/static_modifiers/00_static_modifiers.txt (Static modifiers#Vassal subject).
  3. 3.0 3.1 See in /Europa Universalis IV/common/subject_types/00_subject_types.txt
  4. See in /Europa Universalis IV/common/static_modifiers/00_static_modifiers.txt (Static modifiers#March subject).