It represents a justification for war that is recognized as legitimate by other nobles, religious leaders or whatever the predominant structure may in the case be. The plural form of casus belli is also casus belli (not casi belli, which would be second declension - casus is a fourth declension noun).
As with other games from Paradox Interactive, you need to have a CB to start a war in Crusader Kings II. The CB for the war determines the prize for victory and the price of defeat, as well as frequently determining who can participate in the war and what you need to do to win it.
The rationale and reasoning for CB is that rulers of a certain religion and moral code should not be making war on one another for no reason whatsoever, as it is tyrannical and unjust. Followers of some religions, such as the varieties of paganism, are not confined by this and can wage war on whoever they wish - though they risk holy war if they push conquest for the sake of it too far.
Most wars incur a one-way 10-year truce for the attacker no matter what the outcome was (unless the war ended inconclusively), and these can be seen on any county personally held by the attacking leader. Truces are between individual leaders, so if the ruler of either the attacking or defending realm dies, the truce ends. Breaking this truce will lower general opinion of you of all leaders of that religion (excluding your vassals) and cost 200 + half of your current prestige as well.
- 1 Casus Belli and expansion
- 2 Claim wars
- 3 De Jure wars
- 4 For vassals
- 5 Religious CBs
- 5.1 General
- 5.2 Christian
- 5.3 Muslim
- 5.4 Pagan CBs
- 5.5 Indian religions
- 6 Tributary
- 7 Special
- 8 Government CBs
- 8.1 Merchant republic CBs
- 8.2 Nomad CBs
- 9 Triggered Wars
- 10 Gaining CBs
- 11 Using Your CB
- 12 "War ended inconclusively"
- 13 Names of wars
- 14 Summary
- 15 See also
Casus Belli and expansion
Warfare is a primary way to expand your realm, as most CBs can give you new territory:
- Pressing a personal claim usurps the title.
- Pressing another's claim makes them your vassal if they are lower rank, and: they are your de jure vassal, or of your dynasty, or already your landed vassal.
- De jure wars on counties, as well as subjugation-type wars, vassalize or usurp the target titles. They try to make the current rulers into vassals, but usurp if they cannot, due to the attacker's low rank or the defender holding territory elsewhere.
- Invasion-type wars usurp occupied territory in addition to the war's stated target. Minor holdings in occupied counties are also usurped.
- Holy wars usurp all holdings from infidels.
You can have several CB for a single target, and each has its own goal and reward for success. You should usually choose the CB with the largest reward, although it can be to your advantage to avoid a holy war to reduce the number of possible defenders.
Main article: Claims
The possible outcomes are:
- Upon winning a claim war you will gain the title and you'll gain 100 prestige.
- If it ends in a stalemate you'll lose 100 prestige
- If it ends in loss, the claim will be lost in addition to 200 prestige.
Multiple claim wars on a single title cause all attackers to be hostile against each other. If the target title changes hands (whether due another claim war or any other reason), the claim war will continue against the new controller!
If you have a personal claim upon a title in a realm, you can push this claim to usurp the title.
A ruler with multiple personal strong claims (upon a single realm) can push them all at once. This lets the attacker take all claimed titles in a single war and without waiting out 10-year truces.
Claim for other
You can also push a single claim on behalf of any of your courtiers or vassals. You cannot press claims for women against agnatic titles.
Upon winning, the person you were pushing the claim for will gain this title and their opinion of you will increase by 100. If the claimant was unlanded and the claim is on a higher title, they will also usurp a county from the target, and their opinion of you will increase by a further 100.
Note that if you push a claim that is outside your de jure lands for someone who is not already your vassal or a member of your dynasty, they will not become your vassal upon taking the title. Thus, if you're pushing a claim for a non-dynasty courtier, make him your vassal first by granting him a landed title. Similarly, if you push someone else's claim for a title equal in rank to your own, they will be independent.
De Jure wars
When you are the de jure liege of a title but not its de facto controller, you can press a "de jure claim" to gain control. Unlike personal claims, de jure claims cannot be lost unless you lose control of de jure liege title. Losing a war merely means a loss of 200 prestige and a heavy monetary penalty, while you'll still keep the de jure CB.
De jure claim on county
If you or a vassal hold a duchy, or you personally hold a kingdom or empire, you can push a de jure claim upon one of its de jure counties held by the other realm. Even if the other realm holds more than one county, you can only push a single de jure claim at once.
After winning the war, if the holder of the county is the defender and it's not their only county (including their vassals) you, or the vassal you're pressing the claim for, will get control of the county directly. If it is their only county and they don't have a higher or equal rank title to yours then they will become your vassal (or your vassal's vassal). If it is their only county and they do have an equivalent or higher rank then you will also gain the county directly, and they will become unlanded and their higher titles destroyed.
Vassals are not allowed to use this war against other vassals of their liege if the target is down to its last county. This prevents vassal dukes from "steal" direct vassal counts from a king; it's up the king whether to transfer the vassal count or not.
Success also gives 100 prestige, and if you were pushing the de jure claim for someone else they'll have their opinion of you increased by 100. On a white peace, you lose 100 prestige, and the defender gets 50 prestige with a further 50 being divided among the defender and any allies. On a loss, prestige changes are doubled and you also have to pay a lump sum equal to 4 times your annual income to the defender.
De jure claim on minor holdings
Sometimes you or one of your vassals controls a county and one of the minor holdings (barony, temple or city) in the county is held by somebody outside your realm or is independent. In this case you will be able to press a county claim in order to gain control of all such holdings the defender owns. Prestige gains and losses are half those for a claim on a county, except on white peace, where they are only a quarter of the usual amount. The holding will always be usurped, not vassalized.
You can find minor holdings you do not control by zooming in and looking for extra shields, or by clicking a county and checking whether the upper-right coat of arms is yours. You can also use the ledger to search for independent minor holdings and sorting by realm size.
As long as you're someone's vassal, you can try to achieve independence through war. If you win you'll be free of your current liege, and if the liege you're rebelling from is a king or emperor, crown authority will be lowered one step. If you stalemate you'll lose 100 prestige, and if you lose you'll be imprisoned and lose 200 prestige.
Like with changing law, you cannot use this CB more than one step up the chain. If your previous liege was themselves the vassal of another liege (for example, if you're a count breaking free from a duke who is in turn under a king), you will become a direct vassal of the higher liege rather than becoming independent.
Unlike a faction war for independence, a directly declared war for independence allows the attacker to call in allies. (The defender can call in allies in both cases.) On the other hand, a faction war lets you conspire with fellow vassals (making them temporarily your vassals for the duration of the war, making the war effort more coordinated) and can be started while your levies are already raised and gathered.
A failed imprisonment or refused revocation will result in a "War against the Tyranny" or "Revolt against the Rule" of the liege, depending on whether the action was justified or not.
Upon victory, the liege will be forced to abdicate. Without the Conclave DLC, Crown authority is lowered two steps. With Conclave, the title revocation law is instead set to "disallowed", but only in the "War against the Tyranny" variant of this CB.
- Main article: Factions
A vassal who feels their faction is powerful enough can issue an ultimatum. If their liege does not capitulate, a war begins with the faction leader as the attacker. Each faction goal has a corresponding CB.
The faction leader gains a temporary title of the defender's rank (thus temporarily becoming independent) with the fellow faction members as temporary vassals. They provide a minimum liege levy equal to their own army size.
If your religion views an independent ruler as "infidel" or "heretic", you can declare a religious war against that ruler for a duchy. Muslims can also attack non-heretic Muslims of a different denomination (e.g. Sunni vs Shi'a) who are not busy fighting infidels. You must control a province bordering the targeted duchy (or inside it). It can also be used across 2 sea zones if the attacker or defender is Muslim, or if the attacker is Christian or pagan with their respective Crusades unlocked.
This CB cannot be used within a realm, for instance by a Sunni vassal against a Shi'a vassal of the same liege, or by a heretic vassal against their non-heretic liege. Vassals who do not share their liege's religion are restricted from using the CB even for external wars, unless the vassal and liege are both non-heretics of the same religion group.
If attacked in holy war, pagan and Zoroastrian rulers are permitted to convert to their attacker's religion by decision. This invalidates the CB, ending the war inconclusively. However, the standard effects of ruler conversion on moral authority apply: your religion's moral authority increases by 3% and that of the defender's former religion decreases by 3%.
Upon victory you'll gain 50 prestige and all holdings (as long as they're occupied by you or your allies, or unoccupied) in the targeted duchy. If someone of your own religion owns one of the holdings, they'll become your vassal. If you stalemate (white peace) you'll lose 50 piety and 100 prestige, and if you lose you'll lose 150 piety, 200 prestige, and be forced to pay concessions. The winner's religion gains 3% moral authority for 20 years and the loser's loses 3%.
Note that if you use this CB, nearby rulers of the defender's faith will be able to (and frequently will) intervene in the war, so it is best used when neighbours of the target's faith are engaged in other wars. As with any war against a religious enemy, you should also avoid attacking enemies with high piety if their religion has holy orders available or pagan tribes with high prestige.
Unreformed pagans do not have holy wars. Reformed pagans use a modified version that costs 100 piety to declare and has only a 5-year truce.
In Horse Lords, nomads cannot use regular holy war CB, but reformed Tengri nomads can use the pagan version holy war CB as alternative to prestige based province CB.
Jains do not have any type of religious war. Buddhists instead have a county conquest CB usable against other religious groups.
Main article: Crusades, jihads and great holy wars
This is a special CB only available to religious heads with at least 5% moral authority. It targets all territories in a de jure kingdom held by heathens or heretics. Any ruler of the same religion can join, even vassals. Upon success, the land will be given out in one of three manners:
- If the kingdom title is already held by a ruler of the same religion, that ruler gets the territory.
- If the kingdom title is already held by a ruler who is not of the same religion (for example, a Sunni Jihad for the Kingdom of Anatolia which is held by the Orthodox Byzantine Emperor in Constantinople), the land is given to a same-religion claimant on the title (strong claims get priority over weak ones). If no same-religion claimant exists, the land is given to the war participant with the highest war contribution score. The title can be peacefully usurped afterwards by the de facto controller.
- If the kingdom title does not exist, it is created and both kingdom and land are given to the participant with the highest war contribution score.
In addition, the Moral Authority of the attacker increases by 20% for 20 years, and 500 piety and 1000 prestige are divided among all participants by their percentage contribution, while the loser loses 100 piety and 20% moral authority. As with holy wars, defending pagans and Zoroastrians can convert to the attacker's religion by decision, ending the crusade inconclusively.
On a white peace, the attacker loses 5% authority and 100 piety while the defender gets 2.5% authority, 200 prestige and 100 piety. On a loss, the attacker loses 10% authority, 200 piety, the principal defender gets 10% authority and 100 piety, and a further 300 prestige and 150 piety is divided up among all defenders.
Catholic crusades and Muslim jihads become available in the 11th-12th centuries, or earlier if certain holy sites fall to infidels. Reformed Pagans get Great Holy Wars once either crusades or jihads have been unlocked. Jewish and Zoroastrian Great Holy Wars are unlocked as soon as the head of the respective religion is reinstated. Fraticelli Crusades and Ibadi, Yazidi, Hurufi, and Kharijite Jihads are unlocked once their religious heads are formed, and when the Crusades or Jihads are respectively unlocked. The Indian religions and Eastern Christians (Orthodox, Miaphysite and Nestorian) are the only religions without a Great Holy War of any kind.
Christian, Jewish, and Zoroastrian rulers can ask their religious head to condone an invasion on another realm that follows the same religion and head. You must have a claim on the target or a smaller realm than the target. It costs 250 piety (500 with Free Investiture) and will only be granted if the religious head likes you much more than the target.
Upon victory you'll get the throne in question, 400 prestige, and every occupied holding as well as all holdings in counties where you occupy the capital, and also earn the nickname of "The Conqueror". As such, you should occupy every county before enforcing demands, as then you can install your own nobles. If you stalemate you'll lose 100 prestige. If you lose you'll lose 200 prestige, and have to pay concessions, and you'll lose your claim upon the throne.
This CB is most useful for Catholics. Most Orthodox kings have autocephalous patriarachs, while Jews and Zoroastrians must first restore their respective religious head.
If the target dies, the invasion claim disappears.
If someone has the same head of religion as you, and has been excommunicated, you can declare war upon them. Victory will give you 10 to 70 piety and 50 to 400 prestige depending on the excommunicated ruler's rank, and the target will have his excommunication lifted and be forced to abdicate. A white peace will lose you 50 piety and 100 prestige. Losing will lose you 100 piety, 200 prestige, and you'll be forced to pay concessions.
By default only Christians have excommunication; however if the Yazidi Sheikhdom has been created, the Sheikh can excommunicate fellow Yazidis.
Christians who accept the authority of the 'true' Pope may attack rulers who have established an antipope. On success, the antipope is deposed (meaning he loses his claim on the papacy; he keeps his bishopric) and the winner gets 500 prestige, 250 piety and a massive opinion boost from the Pope. The loser takes a heavy prestige and piety hit. On failure, the attacker loses prestige and must pay heavy reparations.
Vassals of a king or emperor who controls an antipope may start a faction to depose both and install a rival claimant. The faction members can call the real pope into the resulting war.
For 1000 piety, Muslims may seek to conquer all territory in a de jure kingdom belonging to a ruler of a different religion who controls at least 6 counties within it. Winning grants all holdings held by rulers also owning land outside the kingdom, and also transfers vassalage of all subsidiary lords in the kingdom. The new vassals get a temporary +75 relations modifier with you, making it very easy to demand their conversion. Since patch 1.091, this CB is only usable on kingdoms that you border or own land in. According to CB files, nomads cannot use muslim invasion, they use nomad invasion instead.
Unlike other invasions, you only gain the target holdings; the loser gets to keep any holdings you occupy outside the wargoal.
As with holy wars, defending pagan and Zoroastrian rulers can convert to the attacker's religion by decision, ending the war inconclusively.
County Conquest (Muslim)
Muslims may attack any county bordering their own lands. The CB costs 50 Piety to use, but is usable on any target except your liege. You must have the Piety for the option to show up. Victory gains you the county, or (if the county is ruled by a single-province count and you're duke rank or higher) transfers vassalage of the count to you, and gives 100 Prestige. White Peace costs 100 Prestige. Losing costs 100 Prestige and forces you to pay concessions. The truce lasts only 5 years.
Once every 10 years, Muslim caliphs may attempt to subjugate a Muslim de jure kingdom of the same denomination. On success, the target's vassals in that kingdom (or target) become the attacker's vassals. If someone holds territory outside the target kingdom, they cannot be vassalized, so their titles within the target kingdom are usurped instead.
The truce lasts only 1 year. Despite this CB not usurping all occupied titles, the attacker will not accept early surrender. This may be a bug.
According to CB files, nomads cannot use Caliphal Subjugation, they use nomad invasion instead.
Muslims can use this CB to usurp titles from kin with the decadent trait.
County Conquest (Pagan)
Similar to the Muslim CB, but only usable on targets of different religion and does not cost piety to use. All pagans may target neighboring counties, and Germanic pagans may also target any coastal county if it is held by a non-pagan. The Germanic coastal version is only available once the "Start of the Viking Age" event occurs in the 790s. On success, rewards 50 Piety and Prestige in addition to the county, and gives the religion 1% moral authority for 20 years. Like the Muslim CB, the truce lasts only 5 years.
Nomads have access to County Conquest regardless of their faith.
This powerful CB targets a de jure kingdom but does not usurp the kingdom title. As it is an invasion, it also usurps all occupied holdings (and holdings in occupied counties), even outside the wargoal.
Without the "Horse Lords" expansion, it can be used by Pagans with Invasion culture (Altaic or Magyar) and non-Christians with Horde culture (Mongol or Nahua). With the "Horse Lords" expansion, it can only be used by Pagans, and requires Altaic, Magyar, or Nahua culture. In both cases, it cannot be used against Pagans, for whom the Subjugation CB is suggested as an alternative.
Declaring a Tribal Invasion costs 500 prestige, but you get 200 to 400 prestige back when you win depending on war contribution.
Nomads cannot use this CB. Instead, they can use #Nomad invasion when their population is 90% of its maximum.
Pagans may target all land in a de jure kingdom held by another pagan. On success, all holdings are vassalized or seized, and top-level non-titular titles are seized if they are of equal or higher rank than the invader's top title. The conqueror gets an opinion bonus from the vassals he subjugates. Reformed Pagans lose this CB, and are also protected from it, except from attacks from the unreformed version of their own religion. The truce lasts only 1 year.
A character may only use this CB once every 100 years, except with the "Become King" ambition, which allows unlimited usage within the capital's de jure kingdom.
Nomads have access to Pagan Subjugation. The attacker vassalizes ALL of the realm of the target, though only Khagans can target Emperors.
Germanic Pagans may (using a special diplomacy option) declare their intent to attack a realm and recruit followers from all over Scandinavia. The target realm must have between 10 and 40 holdings within a de jure kingdom, while the Norse ruler must also have between 1 and 40 holdings as well as 1000 Prestige. During the two years after the invasion is announced, the Norse ruler will receive free troops and ships. The recruited army scales with the size of the ruler's existing army, and also tends to be larger with:
- 7, 10, 15, and 20 martial skill
- 7, 10, 15, and 20 diplomacy skill
- 100 and 1000 prestige
- Higher rank than count
Recruits slow down once you are 2x more powerful than your capital county levy, and stop once you are 3x more powerful . Therefore, if you plan to use your prepared-invasion army to attack multiple realms, you should target a powerful opponent Pay attention; increase levy in your capital county by all means before prepared invasion. .
As with Holy Wars, neighbors of the target who share their religion can (and very likely will) join in defense. Not declaring war within two years cancels the invasion and has a heavy Prestige cost. On success in the war, all holdings within a de jure kingdom are vassalised, except occupied holdings and holdings in occupied counties, which are usurped. Only usable once per ruler's lifetime. The truce lasts only 1 year.
This CB becomes available following the "Start of the Viking Age" event, which fires between 793 and 867.
Rulers of the Indian religions (Hinduism, Buddhism, Jainism) may subjugate de jure kingdoms held by other Indian rulers. Costs 500 piety, and is only usable on targets of the same culture group. The truce lasts only 1 year.
A character may only use this CB once every 100 years, except with the "Become King" ambition, which allows unlimited usage within the capital's de jure kingdom.
Buddhist county conquest
Buddhists can attempt to vassalize a single county from another religion group. The truce only lasts 5 years.
While called a "holy war" in game, this is deceptive as it does not affect moral authority and does not allow the defender's coreligionists to join.
While smaller than the duchy-level holy war available to Hindus, this CB has advantages if the targeted county is held by a count who holds no other county titles. You can revoke the title from the holder (using religious control law) and have a county that is immediately productive, rather than having a severe conquest penalty to levies.
You can also use this CB to gain control of infidel claimants. A second war, using the claim-for-other CB, can then net you an entire kingdom. With Muslim neighbors, there is even the possibility of gaining control of the ruler's sons or grandsons, letting you game their open succession by granting a kingdom.
A tributary-suzerain relationship is an asymmetric pact, less permanent than a vassal-liege relationship but in some ways more powerful. Tributaries pay tax at a high rate, usually 40%.
Suzerains can force tributaries to join their wars using the "Call to Arms" interaction. Tributaries can request that suzerains join their wars, and suzerains will often join even though they are not obligated. However, suzerains cannot volunteer to join their tributary in defense unless asked. By patch 2.6.1, the dynamic had been altered, and suzerains can now offer to join tributaries' wars.
A suzerain cannot declare war on their tributaries. The pact ends on the suzerain's death, but not on succession in the tributary's realm.
On success, the defender becomes a tributary of the attacker at a tax rate of 40%. Nomadic and tribal rulers get special opinion bonuses with their vassals after winning this kind of war.
This CB has unusually low
defender_ai_defeat_worth. Defenders may surrender immediately upon war declaration if the attacker is significantly more powerful (not considering allies). Distant targets, proud/brave/greedy characters, and kings are less inclined to fold, but may still surrender well before 100% warscore. Re-using this CB a great way to gain prestige upon succession.
Requires "Horse Lords" DLC. Requires a border or being at most 2 sea zones away (similar to holy wars). Can be used by any government type. Primarily used by nomads against the richer government types, but occasionally used by other realms when other CBs are unavailable.
Tributaries cannot declare most wars against their suzerain, but can declare war to free themselves from tributary status.
In the rare case that a tributary becomes a vassal of another realm, their liege can also use this CB on behalf of their vassal.
A super-powered CB available only to the restored, Christian Roman Empire. On success, subjugates all holdings in the target duchy like in Muslim invasions. May only be used on kingdoms once part of the historical Roman Empire (roughly, all of Europe south and west of the Danube and Rhine, as well as England and the Near East west of Persia). Cannot be used on Muslims, but it does not need to be as Holy War is available for them.
Manifest Destiny Invasion
This CB can only be used by Timurids and pre-1200 Seljuks. It targets a kingdom within the de jure empires of Persia, Byzantium, or Arabia. The target realm must control 3 provinces within the target kingdom.
Humiliate and imprison a rival ruler. This targets the person rather than his or her title(s): on victory, the targeted rival is imprisoned by the victor, but no territory changes hands. While of little direct utility other than gains in prestige and wealth, this can have side benefits such as forcing a regency, allowing weak claims to be pressed against the rival's title(s). It is also extremely useful in a republic for boosting prestige, which factors prominently in succession -- suppressing a rival house every time the truce expires can increase prestige enough to edge out the election against a non-rival house in an otherwise close campaign.
Merchant republic CBs
Seize trade post
For patricians and merchant republics targeting each other. Cannot be used against patricians in the same realm if you have 2 or more trade posts more than they do. On success, you gain the target trade post; on failure, you pay reparations. The truce lasts only 5 years.
A republic-only CB added in patch 1.09. Can be used by patricians as well as doges. Usable if you or your vassal patrician control a trade post in the province. Targets a single city within the province. If used in a county with a vassal's trade post, they get the city instead of you. The city conquest CB cannot be used against characters in the same realm as you.
Republic county conquest
Republic-only single county conquest, only usable if you (or your vassal patrician) already control a city in the province. You must either control a neighboring county or one at most two sea zones away. Patricians who don't already own a county can't use this CB.
Usable against merchant republics (or their lieges) who control trade posts in your realm. On success, all trade posts are destroyed and you earn significant money for each one conquered in this way. Unlike other CBs, the Embargo option only appears when at peace.
This CB allows Nomads to subjugate non-Nomadic realms. Empires can only be targeted by emperor-level nomads (khagans).
When subjugating a realm that broke away during Nomadic Succession, the CB is completely free. This is controlled by the opinion modifier "-50
declared_independence_nomad", given to the new khagan toward the breakaway ruler and their dynastic direct courtiers and vassals.
Otherwise, it costs 500 prestige and can only be used once every 100 years. If the war becomes invalid, the launched_subjugation timer is refunded, but the prestige is not.
Can be launched by nomads whose population is at least 30,000 and 75% of max. It might be useful to grant some lands to fellow clans in order to reach the 75% needed for the invasion. Costs 100 prestige.
According to CB files, Nomad invasion works like a crusade. All the territories occupied by your vassal/allies/tributaries will be usurped by yourself. The target realm unoccupied will be vassalized instead.
Also known as "Nomad Expansion", this CB allows any Nomad to vassalize non-nomad or usurp nomad holdings of an independent ruler within a single de jure duchy. It costs 300 prestige. The defender can call (and can be joined by) rulers of the same faith just like in a Holy War. It has a 10 years truce, contrary to a 5 years truce for county conquest or reformed tengri holy war.
Feuding clans can declare wars against each other to seize a single county.
Minor clan revolt
A khan can use this CB to replace his liege as khagan. It is triggered either by refusing a tyrannical action, or by delivering an ultimatum as the leader of an "overthrow khagan" faction. On success, the war leader usurps empire-tier titles and executes the previous khagan.
Liberate duchy from nomad
Non-nomads can use this CB to take a duchy from a nomad realm. Requires a county in the target kingdom, a border, or being at most two sea zones away. Vassalizes non-nomadic rulers and usurps other titles. AI rulers are more likely to use this CB when the duchy contains castles or cities.
Used against another nomad to steal 300 prestige and 25% of their population.
These CBs cannot be used by the player, but are triggered by events. In each case, a large army appears under the command of a landless leader. On success, the ruler takes all occupied territory, and possibly higher-level titles as well.
Main article: Revolt
Without The Old Gods DLC, revolts take the form of a leaderless army that's hostile to everyone, but not at war with anyone; sometimes they will capture a province, but just as often they will disperse. With the DLC, though, they actually have leaders with titular rebel titles and they declare war on you with a special CB. There are four types:
- Nationalist rebels ("Persian Liberation Revolt") appear in foreign-cultured provinces that were once part of a kingdom or duchy of the province's culture. They are usually quite large. On success, the leader becomes an independent ruler of the culture. with the kingdom or duchy title and the nickname "The Liberator."
- Religious rebels ("Persian Zoroastrian Uprising") and heretic rebels ("Persian Manichean Uprising") are two different types, but similar. They appear in provinces of heretic or infidel religions. In the case of a heretic revolt, the leader has the Heresiarch trait. They are medium-sized. On success, the leader becomes a count-level independent ruler.
- Peasant rebels ("Shirazian Peasant Revolt") appear in rebellious provinces not meeting either of the above criteria. They are relatively small and the leader has the Peasant Leader trait. On success, he becomes a count-level independent ruler.
In all four cases, the truce from the war lasts only 1 year. Except for peasant revolts, they usurp all occupied counties and their minor holdings, like a tribal invasion.
Main article: Adventurers
Landless claimants to a title may declare their intention to press their claim and recruit an army. Norse, Frankish and Norman nobles without any claims may also attempt to conquer a coastal duchy. In both cases, assassinating the leader before the war starts stops the invasion. When the war starts, the adventurer gains a duchy-level titular title named after him (e.g. "Arnulf's Host"; if he's pressing a claim, the war is called e.g. "Arnulf's Host Claim on Sicily War", otherwise "Arnulf's Conquest of Sicily" which is a special CB). Adventurers have fairly large armies (typically about as big as the total levies of the targeted realm) and are quite dangerous. They automatically receive a treasury of 500 gold. If defeated, they may be banished, netting the ruler all of their money.
Muslim dynasties with at least 75% decadence that rule a duchy or higher may draw the ire of a desert tribe determined to end their corrupt rule. The invasion begins in a random realm province with a very large army appearing. Upon success, the invader gets the top-level titles of the old ruler, as well as getting all occupied holdings and counties (like a tribal invasion). The invader also gets the nickname of "the Conqueror." The Crown Authority of the invaded kingdom is set to Autonomous Vassals. Duke-level or higher vassals will get the option to proclaim their independence from the new authority; as of patch 2.3 the invader no longer gets claims on their titles. On a white peace or failure, the invader is imprisoned by the ruler.
Rise of the Shia Caliphate
A special targeted invasion that may appear in any Sunni kingdom or empire with at least 10% decadence if no Shia caliph exists. A Shia child leader with the Quick and Sayyid traits appears holding the duchy-tier titular title "Pretender Shia Caliphate"; the CB is "Shia Caliphate Rising in [kingdom]" e.g. "Shia Caliphate Rising in Egypt". Human-controlled Sunni realms are much less likely (MTTH 10x greater) to be targeted.
His invasion begins in a random province and invades its de jure kingdom (as long as he has at least 6 counties in it and the liege title isn't held by someone else). If he wins, he takes the kingdom title and becomes the Shia caliph, in addition to the usual "tribal invasion" type result of vassalising its de jure vassals and usurping any occupied holdings and counties. The truce lasts only 1 year, so the caliph may well attack his original target again very shortly.
- This section is Christian-centric, and most of it could be merged into Expanding your realm.
While some of these CBs you'll have merely due to your position, like the independence CB and the law change CBs, many of these can be gained on purpose.
First, the easiest type of CB to gain are claims. There are four primary ways to gain claims:
- Have your chancellor forge claims. This doesn't work for anything above the ducal level (skill of 15 needed to forge a ducal claim)
- Marry someone who has an inheritable claim. Your children will have the claim and you can then push it
- Marry someone in your dynasty to someone who has an inheritable claim. Their children will have the claim, and you'll be able to push it
- Invite someone with a claim to your court. You'll then be able to push it
Expanding your realm outside your de jure borders using claims can be tricky: unless they're of your dynasty, a landless claimant to such a title will become independent when you win their war. If you want them to be your vassal instead, you will want to land them first. Since you get a +100 "Pressed my Claim" opinion bonus, you might be able to offer vassalization afterwards, but only if they're the same religion and culture as you - otherwise the "False Religion" and/or "Foreigner" penalties, along with "Not my de jure liege", mean they're unlikely to accept.
Second, de jure claims are also relatively easy to gain. If you can create a duchy or kingdom that overlaps another realm's territory, this will gain you a de jure claim, and the same applies if you usurp it. In addition, after pushing a claim for a duchy, you'll often have de jure claims.
Third, excommunication CBs are easy to get as long as the religion head likes you, but these won't help you grow your realm. They're good for gaining some prestige, though.
Fourth, you can get religious war CBs on essentially the entire world if you convert to a heresy (a Catholic-derived heretic will have CBs on all rulers except Orthodox and Miaphysite ones or other Catholic-derived heretics, while a Muslim heretic will have CBs on absolutely everyone except other followers of the same heresy). The easiest way to get heresy to appear so that you can convert is appointing an antipope, as this lowers the moral authority of the church. The lower the moral authority of the church, the more likely heresy is to spread. Then upon the first chance you get, you should change to whatever heresy arises. Another option is to have your court chaplain research cultural tech until a heretic find appears. So while the drawbacks of heresy are severe (-30 opinion with all non-heretics, and increased rebel risk), the advantages when it comes to expansion are huge. However, note that it's a two-way street - if you convert to a Catholic heresy then all Catholic rulers get a Holy War CB on you, and the Pope may even declare a Crusade against you.
Fifth, the pope will award strong, uninheritable claims to counties and duchies held by Catholic rulers, in exchange for some prestige and an opinion penalty. If the pope is your vassal (emperor level who claims the papacy in the name of his antipope will receive the new pope as vassal), he will never refuse a request, regardless of opinion modifiers. This allows you to obtain one county or ducal claim per 100 piety (or 50 piety with papal investiture). You can use request claim to obtain any number of claims and then utilize "Claim all" CB. This strategy allows you to conquer vast amounts of land, even entire kingdoms with enough piety, in a single war, and allows you to appoint new count and duke level vassals on the newly conquered territory.
Using Your CB
Pushing your own claims and similar is rather straight forward. When pushing someone else's claim however you have to be careful, or they'll end up as an independent realm. They'll only be your vassal if they are already your vassal, they're in your dynasty, or the claim you pushed was for an area that is de jure part of your realm. If the title they took is at the same level as yours or above they'll be independent even if any of the above conditions apply, unless you have a liege above you where the conditions still apply.
The easiest way to ensure that they'll be part of your realm after pushing their claim is granting them a county or barony in your realm first. The only way they can become independent then as a result of the claim pushed, is if the title they gain is at the same tier as yours, or higher. It should be noted that Hindu characters cannot be granted a holding which his caste cannot hold.
"War ended inconclusively"
Sometimes a war ends not with one side winning, or a white peace, but inconclusively. This happens when the war can no longer be pursued for some reason - usually because the casus belli is no longer valid. This does not, however, mean that a CB that could no longer be used leads to a war using it becoming invalid; the invalidation and usability conditions are separate, though usually related.
Some common messages are:
- [War name] ended inconclusively (Casus Belli no longer valid)
- This means that the war has become completely unjustifiable. For claim wars, this may mean the claimant died or the defender lost the wargoal for some other reason. For holy wars and crusades, it may mean the defender changed religion to one that can no longer be the target of such a war, usually by the special decision for converting to the attacker's religion. Note that a successful claim war won't invalidate other claim wars on the same title - the war simply continues against the new holder.
- [War name] ended inconclusively (Liege Change for [Defender])
- You can only attack someone if either their direct liege is one of your lieges, or they are independent. When they become a vassal of someone who isn't your liege, the defender isn't a valid target any more, so rather than transferring the war to the new liege, the war simply ends. This frequently happens when attacking rebelling vassals when their rebellion ends. Again, note this doesn't invalidate other claim wars on the same title, which instead transfer to the new holder - even if he is a vassal.
- [War name] ended inconclusively ([Defender] became unlanded)
- This is pretty self-explanatory. The defender lost all his landed titles for some reason (perhaps in another war or due to his liege revoking all his titles), and is no longer a valid war target.
- [War name] ended inconclusively ([Defender] joined [Attacker's Liege]'s war as attacker)
- A vassal warred an independent realm allied to his liege, but the liege then called the independent ruler to war as an ally. This overrides the vassal's war.
- [War name] ended inconclusively
- Without further explanation, this probably means the war was a faction or plot war and the leader died. With the leader gone, there is no one left to enforce demands, surrender, or sign a white peace, and so the war ends.
Names of wars
You can identify what Casus Belli was used to declare a war by its name. In addition to the examples below, there may be an ordinal prefix indicating that this is the Nth war of that name to have been declared (several may be ongoing at once, e.g. "Byzantine Holy War for Syria" and "2nd Byzantine Holy War for Syria" might be declared at the same time, both targeting the de jure Emirate of Syria, but the parts of it in two different realms).
For some wars, the result is that someone "gains or vassalises" one or more titles. This means that titles that can be vassalised are vassalised, and all the others are gained. Generally a title is gained if vassalising would end up also vassalising a title that wasn't being targeted. For example in the case of a holy war targeting a duchy in which one of the counts had land outside that de jure duchy, the attacker doesn't become their new liege, but just usurps the target titles.
Casus belli and claims are easy to gain as long as you know what you're doing. Following these tips you should be able to expand easily.
- Most wars incur a truce which lasts either 10 years or until the death of one of the war leaders.
- Marry claimants with inheritable claims to gain more claims
- Marry your dynasty members to characters with inheritable claims (marry male claimants matrilineally if possible)
- Invite males with inheritable claims and grant them a county
- Invite pretenders and grant them a county
- Make the pope love you and you can farm prestige off of excommunication
- Go heretic and you'll have CBs on everyone
- Create or usurp duchies or kingdoms that overlap the territory of other realms
Additionally, different CBs have different values to you as a ruler. If you have more than one CB, consider pressing them in this order:
- Invasion/Crusade - you gain all land you occupy under the Kingdom title
- Holy War - you gain all heretic/infidel held land in the targeted duchy
- Personal Claim - you can fill up your demesne or select the new holder of the county yourself, can push more than one on a given ruler at a time. Note that you don't get the title's vassals although they become your vassals.
- County Conquest - costs piety can only be pressed one county at a time
- Seize County - you've already got one barony in this county, but this gives you the other 2/3rds of it.
- Dynastic Ducal/County Claim - install a member of your dynasty and add land to your realm.
- Vassal Ducal/County Claim - expands your realm, but the new holder isn't of your dynasty and you're making one of your current vassals more powerful
- Dynastic Kingdom Claim - unless you're an Emperor, this will install a dynastic ally into a Kingdom who can help you in future wars.
- Seize Coastal City - you're only getting one barony-level title out of this.
- Embargo/Excommunication - Great for bringing in money or prestige/piety, but won't expand your realm.