Waging war is one of the primary ways to attain territory.
Main article: Casus Belli
In CK2, wars are fought over Casus Belli. The CB you use has a direct impact on how you wage your war, and defines the possible outcomes:
- Enforce Demands
- White Peace
There is also a fourth option: ending inconclusively, which happens when the CB becomes invalid, the defender's liege title changes, the defender becomes unlanded, or (depending on the CB) the attacker dies.
Main article: Levies
You cannot declare war if you have any levies raised.
There are two kinds of levies:
- Levies from your own demesne holdings: when raised altogether they will start with 100% morale.
- Levies from your vassals: they will start with 0% morale.
The number of levies you can raise from vassals depends on:
Ships are used to transport troops, and by pagans to store loot when raiding coastal counties. Each ship carries 100 troops. There is no naval combat or blockading in the game. Ship levies are very expensive when raised, costing 0.3 ducats per ship per month (although pagans receive a 90% discount). Non-pagans should dismiss ships when they are not immediately needed.
Ships are provided by buildings unlocked with the Shipbuilding technology, as well as by the family palaces of patrician families. In the 867 start, only Norse pagans, Byzantines and Muslims have this technology available. Starting in 1066, ship-only mercenary bands become available, letting landlocked rulers have access to sea transport, albeit at a very steep cost.
Main article: Retinue
Retinues are your private standing army.
Mercenaries are troops that can be hired for a price. They can be hired from the Military screen on the Mercenaries Tab. Note that not all regions have mercenaries available, and those that do can have different quantities available.
In addition to the initial hiring fee, they have upkeep fees which are much higher than any of your own troops'. Be sure that you have plenty of money to pay them. Mercenaries who do not get paid will at best disband themselves, and will at worst defect to the enemy or declare war on you (which can even happen in the middle of a battle).
Also, when hiring mercenaries, the full force of their unit may not be available if their previous employer disbanded them while they were not at full force. They will gradually replenish their manpower over time. It is easy to mistakenly hire a mercenary band and then realize that you have only hired a few hundred troops rather than the few thousand that you expected - pay careful attention to their manpower on the mercenary screen to avoid this mistake.
The cost of hiring a troop does not vary based on how many units they currently possess, but the cost of maintenance does decrease as the mercenaries take casualties. For this reason, and because mercenaries can replenish casualties while on the field (standard levies do not replenish on the field), it is beneficial to put mercenaries wherever casualties are expected to be highest. The monthly upkeep of a company depends on that unit's current size. A thrifty and unscrupulous ruler might deliberately waste half of a company in a futile assault in order to save money.
Each mercenary company has a predefined capital province, and may also have predefined cultural or religious requirements. You may only hire a company if your capital is within a certain distance of the company's capital and if you meet the religious and cultural requirements.
Mercenary troops can only be hired by one character at a time - therefore it is very possible that, at any given time, all the mercenaries which are within your price point may be unavailable because they have been hired out by other realms. If your war strategy depends on the hiring of mercenaries, ensure that you check mercenary availability before declaring war. You could even hire them before the war starts (it's only levies that prevent you from declaring war).
The composition ratio of the company is fixed, but the actual number of troops increases with time, based on size and current year.
Mercenary companies may become landed (it's not uncommon to see Venezia ruled by the Company of the Hat) and can sometimes be vassalized. If a mercenary company is a vassal, only their liege can hire them.
Holy orders are similar to mercenaries in that they can be hired and are independent of other realms. Holy orders cost Piety to hire instead of gold.
- During great holy wars, as well as when defending against infidels, they have free upkeep.
- During offensive wars, however, they have a substantial gold upkeep cost.
The most important fact about holy orders is that they will not fight enemies of the same faith as them, so make sure you point them in the direction of heretics and infidels!
Holy orders are created by events when certain conditions are met, and always join the mainstream religion (which can be an heresy if it has become mainstream).
|Knights Templar||Catholic||Crusades unlocked and either
|Knights Hospitaller||Catholic|| Crusades unlocked and either:
Crusades unlocked and either:
|Knights of Calatrava||Catholic|| Crusades unlocked and either:
|Knights of Santiago||Catholic|| Crusades unlocked and either:
|Brotherhood of the Holy Sepulchre||Orthodox||Counties of Antioch and Jerusalem are Orthodox and owned by Orthodox characters.||
|Order of Saint Anthony||Miaphysite||Counties of Alexandria, Makuria and Aksum are Miaphysite and owned by Miaphysite characters.||
|Order of Saint Addai||Nestorian||Always available to Nestorian characters.||
|Bektashi Order||Sunni|| Sons of Abraham DLC, Jihads are unlocked and either:
|Zealots||Judaism||Jewish high priesthood is restored||
|Immortals||Zoroastrian||Zoroastrian priesthood is restored||
|Jomsvikings||Reformed Norse|| Norse reformation
|Lords of the Sky||Reformed Tengri||
Sons of Abraham DLC and Tengri reformation
|Spirit Guardians||Reformed West African||
Sons of Abraham DLC and West African reformation
|Warriors of Perun||Reformed Slavic||Sons of Abraham DLC and Slavic reformation||
|Chosen of Perkunas||Reformed Romuva||Sons of Abraham DLC and Romuva reformation||
|Sons of Kaleva||Reformed Suomenusko||Sons of Abraham DLC and Suomenusko reformation||
|Cult of Huitzilopochtli||Reformed Aztec||Sons of Abraham DLC and Aztec reformation||
|Chosen of Ashoka||Buddhist||Rajas of India DLC||
|Followers of Arjuna||Hindu||Rajas of India DLC||
|Bulls of Rishabha||Jain||Rajas of India DLC||
Vassalizing mercenaries and holy orders
Some mercenaries and holy orders are vassals of feudal lords in historical starts, or can become vassals by special decision. Others can become vassals, but only under certain circumstances if they become landed:
- A landed mercenary company or holy order will, like any independent duke-tier ruler, accept diplomatic vassalization if the requester is an emperor-level, same-culture, same-religion neighbor whom the company's head likes.
- A landed mercenary or holy order will produce claimants upon succession (since they use Open Elective succession, in which each vassal can vote; with multiple vassals there will be multiple votes cast and the second- and third-place candidates get claims). Inviting a claimant, landing him, and pressing his claim will make the company your vassal.
A vassal company can only be raised by its liege, and at 1/5 the regular cost.
Attrition happens when the number of troops in a province is higher than the supply limit of that province.
The supply limit of a province is based on terrain and modifiers:
Supply Limit = (Base Supply + Terrain Supply - Disease penalty) x Supply Modifiers
- Base Supply is 5K.
- Terrain Supply is 5K for plains, 3K for forests and hills, 2K for mountains, 1K for deserts and arctic.
- Disease penalty is -4K for epidemic diseases.
- Supply Modifiers are:
- Coastal Province: +50%
- Controlled Neighbouring holding: +75%
- Technology boost from military organization in capital: +12.5% per level, up to +100%.
- Own realm: +50% per holding
- Neutral holding +25% per holding
- Occupied holding +25% per holding
- Hostile Holding -10% per holding
- Pagan homeland: -95%, if the religion of the province is an unreformed pagan.
- If Military Organization IV has been researched in your capital county, this modifier is nullified.
If an army exceeds the supply limit of a province, a percentage of troops will die every month due to attrition:
- Base land attrition: 5%
- Terrain modifier: +2.5% for forests and hills, +10% for mountains, arctic, and deserts
- Epidemic disease: +5%
- Army leader: -0.1% x martial skill of army's centre commander.
The value above represents a maximum attrition that can occur. However, if the percentage of troops over the supply limit is low, only a portion of the maximum attrition will occur.
Your goal is to raise the warscore to 100%, which will force your opponent to accept your demands. You opponent may offer to surrender before that, but at 100% he MUST surrender. If you're on the defensive, or need to bail out of the war, you can also seek White Peace when the war has gone on for a bit and the warscore is still near even.
Warscore can be gained in four ways:
- Winning battles against enemy armies.
- Sieging down and occupying enemy holdings.
- In some CBs, the warscore will tick up or down if the targeted province is fully in the attacker's or defender's hands.
- Holding prisoners. If the leader of a war is captured, warscore becomes 100% in his enemy's favour. Captured close relatives of the war leader also affect the war score.
Warscore gains from victories in battle or from occupying holdings are larger if they're against the war leader as opposed to his allies. Battles have half their usual warscore value in crusades.
Main article: Combat
It is possible to set game difficulty before start. It ranges from very easy to very hard and morale of both your levies and the AI is affected.
|Army Morale||AI Army Morale||AI Reinforcement Rate|
All holdings have a basic garrison, which increases in size if certain improvements are constructed. Holdings also have a levy which can be raised. When sieging, you will need to have more troops in the county than the defenders have in their garrison plus levy. If the attackers do not have enough men, no progress will ever be made on the siege. Note that a liege can raise his vassals' troops and the vassals' garrisons will show their levy strength as being at full manpower. However, a character who raises the troops from his (or her) own demesne will have those raised levies taken out of the garrison. This means that it is much easier to siege the holdings of a liege who has raised his demesne troops than it is to siege his vassals.
If the attackers do have enough troops, every 12 days a tick will count and progress will be made on the siege. The amount of progress that is made per tick depends on the fortification level of the holding and how severely the attackers outnumber the defenders.
Whether slowly or quickly, once a siege reaches 100% progress, it will be occupied by the attacker and warscore will be awarded.
Eventually, the attackers will be able to assault the defending garrison. The amount of time it takes for this option to become available depends on the holding's fortification level and how much the attackers outnumber the defenders. If an assault is ordered, the attackers will start losing large quantities of troops while accelerating the siege progress substantially.
When assaulting, it is recommended to have 10x the number of troops involved in the attack as the defenders have in their garrison. This will minimize the attacker's casualties, as the defenders are overrun and unable to maintain any level of adequate defense. Assaulting is based on the skirmish value of the unit, making archers rather good at assaults.
The Home Front
If you are in an offensive war (except Crusades) and raise your vassals' levies, you will gradually incur a stacking opinion penalty, -1 for every 61 days (approximately two months). This penalty will increase as long as your vassals' levies are raised, and will slowly decrease at the same rate it increases. So if you're at war for 4 years, your vassals will end up with a -20 opinion of you which takes 4 years to wear off. If you're a long-reigning ruler with high diplomacy and good vassal relations, this is merely annoying. If you're barely keeping a lid on the dissent as it is, this can be extremely problematic. You can avoid this by calling as few of your vassals' troops as possible or by ending the war as quickly as possible.
Additionally, if your personal levies and retinue get depleted, you could have issues with factions, as they measure the strength of their members against the number of troops you can raise. If half your personal troops are killed off, the power of those factions will increase dramatically, making them more likely to make demands or rebel. This is potentially compounded by more members joining the factions as their opinions of you drop due to the raised levies. Losing many troops is, however, one way to trick a faction - which would normally be too weak - into revolting, thereby allowing you to crush a relatively weak faction and revoke their lands at a mildly convenient time, rather than risking them continuing to gain power and strength and revolting at a truly inconvenient junction. This assumes that you have the wealth to buy mercenaries or that the faction is weak enough to not steamroll assaults through your holdings - you will probably need a bit of time to replenish all those troops you lost, after all.
There are certain strategies you can employ to improve how well you do in war. Many of these strategies are common sense, but I'll mention them anyway.
Attack a weakened enemy. If your enemy is deeply unpopular with his vassals, has just lost an offensive war, is dealing with a rebellion, or is fighting a war over a different CB, you can beat him more easily. Be aware, however, that a war against a rebelling lord will end if his rebellion ends.
Raise only the vassal levies you need to avoid unnecessarily angering your vassals. If you only need the troops of a single vassal to fight a war, only raise those troops. This vassal will now be the only one getting annoyed at you, while the rest will continue to be happy. The other vassals' levies can then be raised later if ever needed. If you're rich enough to support it, you can also consider using only your own levies and retinue, as then no one will be getting annoyed with you.
Raise vassal levies in the best location. You can raise your vassal's "liege levies" in any county belonging to his sub-realm. This is especially powerful if you plan ahead by giving each major vassal a well-placed county (coastal or near your enemies). You can even disband a levy in one place and immediately re-raise it in another.
Consider hiring mercenaries. They can pay for themselves if they allow you to win a defensive war, or allow you to storm castles rather than slowly siege them. Pay attention to what units you're actually hiring, and try to avoid mercenaries that are high on light infantry and archers, instead going for heavy cavalry and infantry.
Bankrupt your enemy. His armies will lose a quarter of their morale, and his mercenaries may turn on him or even join you. You can drain your enemy's cash reserves and deny him income by capturing his demesne holdings. (His yearly income and expenses are shown if you hover over his cash balance, and his budget details are visible in his demesne screen.)
Target part of an enemy's army while it is split up. While you might not be able to defeat the entire enemy army at once, you're likely to be able to defeat half their army, and the rest is then easy to mop up.
Bait enemies into taking attrition. Using an army smaller than theirs you can continuously pull back, leaving them in a province where their units will slowly die. Only works against large armies or when playing as pagans. Does not work against the attrition-free doomstacks of the Hordes.
Bait enemies into attacking smaller armies, then send in reinforcements. Immediately once combat has started, send in your larger army. If the enemy can't see your reinforcements due to fog of war, even better: you can have your reinforcements already be on the way by the time the battle begins. This means you won't have to spend half an eternity chasing the army down, instead being able to quickly destroy it in a single or a series of decisive battles.
Avoid splitting your army up into pieces smaller than the total size of the enemy army. If you do, you risk losing a large part of your army, and being reduced to a position where you can no longer fight back. If you have a really good reason to do so, go ahead, but make sure you keep the rest of your army close. (You can see your enemy's army size in the ledger, or the realm tree accessible from his portrait.)
Use Organizers to move armies faster. Useful for gathering your levies, chasing down scattered enemies, and beating enemies to defensive positions.
Assassinate enemy flank leaders. In larger battles, 50 gold may be worth it to remove a skilled flank leader and send your enemy's army into disarray.
Utilize the mobility ships give you. You can transport units much faster by ship than on land, which can enable you to quickly strike at isolated enemy armies, then retreat back to sea. However, bear in mind that unless you're playing a version older than 2.0, morale of troops is capped at 50% when on board ship; sometimes it's better to wait for your army to march into position.
When being chased, consider sacrificing a small number of men to let the rest escape. Let a few men remain while the rest go to another province where they can hopefully recover or merge with a larger army. Make sure you leave more than 1/25 of the enemy army, as anything less than this will be destroyed instantly, and as such will not slow the enemy's advance down.
Disband any levies that are doomed. You'll lose half your men if not in friendly territory, but you won't lose warscore. And you can re-raise the levies immediately in another location.
Consider what will give you the most warscore. You may be able to get to 100% and enforce demands without certain battles or sieges, or even without really appearing to have the upper hand.
- Winning battles gives warscore based on the number of enemy soldiers killed. Defeating the entire enemy army will net 75% warscore.
- Occupying enemy territory can give up to 120% warscore, with significant bonuses for the enemy's demesne (which tends to be easier to capture due to depleted levies), capital, and the territory contested by the CB.
- Continuously occupying territory contested by the CB will slowly add warscore (but you only get this "ticking warscore" if you occupy all of the wargoal).
- Occupying all enemy holdings gives automatic 100% warscore.
- Capturing the enemy's close relatives in battle or siege gives you 5% warscore per head, except the heir, who gives 50%. Consider this before sending your own family members into battle.
- Capturing the enemy in battle or siege give automatic 100% warscore. His portrait will tell you which army he is leading, if any.
By outmaneuvering or overpowering the enemy you'll be able to win most battles, and eventually the war itself. Some overall tips:
- Construct buildings to increase the size of your army. More detail in the guide on construction
- Research relevant tech, it can give you the edge you need. More detail the guide on technology
- Appoint good commanders. Gain good commanders through marriage and invites
- When hiring mercenaries, go for heavy infantry and cavalry
- Keep your vassals happy
- Strike the right balance between levy law and opinion. More detail in the guide on levies
- Don't raise more troops than you need
- Ambush the enemy if possible
- Slow down the enemy's advance by sacrificing units if needed
- Go for the wargoals first
- Go for 100% warscore ASAP
- Divide and conquer
- Utilize the mobility ships give you
- Avoid attacking across rivers and into hills