This article may contain outdated information that is inaccurate for the current version of the game. It was last updated for 1.7.
A vassal is a semi-independent nation that owes allegiance to a suzerain 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
There are three different ways to vassalize a nation. Countries can become vassals in the terms of a Peace, in a diplomatic action, or upon receiving autonomy from a larger country. It is not possible to create a vassal if the differences in tech group is too big: a difference in technology cost of 50% or larger will require the relation to be a protectorate rather than a vassal, unless the target is in the Nomad tech group; e.g. it is possible for a Western nation (100%) to vassalize Eastern (120%), Ottoman (125%), Muslim (140%) groups as well as other Western nations, but not Indian (150%) and lower groups. Since this is relative, Eastern nations can vassalize Indian, Chinese and Sub-Saharan (160%), but not Mesoamerican (250%) and below.
Release a nation
To release a nation whose lands you control you must be at peace. The method of releasing a nation is as follows:
- Bring up the Diplomacy menu.
- Ensure that the menu displays information for your country. In the bottom right hand corner of the menu click on View Own Country if the player's country is not shown.
- In the bottom right hand corner of the menu that pops up, you will see the button called Create Vassals.
- If the button is gray and not clickable then you either have no nations to release or you are at war.
- Click the Create Vassals button and choose the nation you wish to release as your vassal. Nations are eligible for release when the following conditions are satisfied
- Target nation does not currently exist
- You control provinces that have the target nation's cores and 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.
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.
Force vassalization (military)
In order to force vassalize a nation, you need to be at war with them. In the negotiations screen, you can find the option under the menu 'treaties' which should be the farthest right menu button on the screen. When force vassalizing someone, the warscore needed is determined by the base tax of all their provinces. Sometimes, the base tax is too high to vassalize the target nation. Typically, a nation of 5-6 provinces or fewer can be vassalized. In some instances it can be cheaper to take some provinces and vassalize the rest if the cost of vassalizing the whole country is too great.
Generally only countries of 4 or fewer provinces can be vassalized via war. The maximum war score is 100% and provinces typically cost 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 for the annexing country. However, pagan countries can be annexed when fully occupied regardless of war score. Vassalizing, releasing, and then diplomatically annexing a pagan country is an excellent way to gain a lot of core territory cheaply, provided the player is willing to wait the required 10 years.
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 downside to the military victor of choosing vassalization instead of annexation are:
- Once integrated the Local Autonomy of every province will be raised to 75%, instead of 50% if taken in war without a claim
- Longer duration until the land is part of the victors country, as you have to wait 10 years in addition to the time that it takes to integrate a country.
Offer vassalization (diplomatic)
In order to offer vassalization to a nation, you must meet these requirements:
- Have a military alliance with the target nation.
- Be in the same religious group.
- Have a relation of 190+.
- The target country must be at peace.
Other factors such as your diplomatic reputation, relative size of military and relative base tax also come into play:
- +20 to -20 from trust/distrust
- +30 to -90 from base tax. Determined by
60*(your base tax)/(target's base tax)^2 - 90, where base tax is the total province base tax of the country without any buildings or modifiers. In addition the base tax of your vassals multiplied with your vassal income efficiency counts towards your base tax [see discussion page]
- +20 to -40 from relative size of military
- +10 Friendly or Threatened attitude
- +10 Having a royal marriage
- +3 per point of Diplomatic Reputation (Rounded down to nearest whole number)
- -1000 if not a strategic interest
- -1000 if not same religious group
- -1000 has more than 40 total base tax
- -1000 has vassals of their own
- -1000 Elector of Holy Roman Empire
- -100 Hostile or Outraged attitude
- -30 Member of Holy Roman Empire
- -20 Neutral attitude
- -30 if either country is a Merchant Republic
- -10 if different religion
- [Verification needed] per distance
- [Other factors?]
Hover over the cross or check-mark in the "offer vassalization" button to see whether they would accept an offer or not.
Benefits of vassals
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. They give 10% of their tax to the suzerain, increased by +25% by the feudal and elective monarchy and archduchy governments, by +33% by the iqta government and following other modifiers:
Note: As of version 1.8, vassal income is calculated using the vassal's vassal income modifiers, not those of the overlord. This makes vassal income modifiers entirely useless.
Vassals increase the suzerain's land force limit, but not naval force limit. 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.
With the Art of War DLC a suzerain can also change the vassal into a march, thus reducing the income he recieved and making it un-annexable until the status is revoked (for the price of -1 stability and -200 relations) in exchange for increased forcelimit, defensiveness, and manpower.[exact bonus?]
If a march gets more than 60 base tax , it will lose its march bonuses while keeping the status. 
A vassal that has at least one province within coring range of its suzerain can potentially be annexed as the result of a diplomatic action. After 10 years and if the vassal has +190 relations with the suzerain, the suzerain can take the diplomatic action Annex Vassal to start the process of incorporating the vassal's provinces into the suzerain country. The original date on which the vassal was acquired can be found in the diplomacy tab of the vassal on the tooltip for the vassalage icon . Once annexation begins, relations may drop without any effect.
Annexing occupies a diplomat until complete. The base cost of annexing a vassal is 10 diplo points per base tax multiplied by hostile core creation modifiers, spent at a rate determined by
- +1 base
- +1 if same culture as suzerain
- +1 if same religion as suzerain
- + or - suzerain's diplomatic reputation (rounded down).
If the total is 0 or negative, annexing will pause, but not go backwards. When all the diplo points are spent, annexation finishes and the suzerain will see the following effects:
- - 3 Diplomatic reputation for ten years. Doesn't stack.
- Relations with other vassals -30. Stacks.
- Relations with other HRE members -25, if the vassal was in the Holy Roman Empire.
- Control of all the vassal's provinces, army, and navy. This may put the suzerain well over its force limit.
- Cores on all the provinces that the vassal had cores on.
- All of the former vassal's provinces not a core of the suzerain before integration will have 75% autonomy (or their previous autonomy level, if above 75%).
Diplomatic annexation strategy
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.
- 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 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 +15 (decays/year)[verification needed]
- Giving war subsidies, up to +15 (decays/year)
Choosing a vassal
A good candidate for diplomatic annexation has the following:
- Lots of cores: this makes feeding the vassal easier.
- Lots of unowned cores or claims: wage war with other nations and force them to return cores to your vassal in a peace deal.
- Small province base tax: a vassal must be economically much smaller before it can be diplomatically annexed.
- Not a Merchant republic, they have a malus for accepting vasslization.
- No Hostile core creation modifier
Feeding a vassal
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.
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. 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 and take 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 will not work if you've already started the annexation process. Countries who are already Vassals will only buy provinces that are either cores, claims, 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. Vassal countries will also cease fabricating their own new claims with neighboring countries, though they may occasionally get them by event with their rivals. Also the province you want to give away needs to be in your coring range (which is the case with any province that is either adjacent to a core of yours or in the official range of one of your cores or your subjects' cores).
It is much easier to sell provinces to countries that aren't yet your vassal, 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).