The best way to expand your character’s Realm is through Warfare. By using your Army to take titles by force. All wars that you are the attacker will require a Casus Belli, which provides a war Objective and sets the consequences for both the winning and losing sides. The three outcomes are Surrender, White Peace and Enforce Demands. You will not be able to declare war if you are in Debt.

Warfare Combat Phases

Battles begin once two hostile armies enter the same Barony holding. At the start of any battle, the terrain that the Barony is on determines Combat width or how many troops are able to fight each other at the same time. Then each battle will go through 4 phases:

LogoPhase Phase Details
Maneuver phase.pngManeuver PhaseThe armies prepare for battle and the Commanders make their initial Advantage rolls.
Early battle phase.pngEarly Battle PhaseThe armies fight and inflict damage upon each other daily and cannot retreat. If an army is defeated this phase, all Routed Casualties become Fatal Casualties.
Late battle phase.pngLate Battle PhaseThe armies keep fighting and keep inflicting damage upon each other each day until either all soldiers on one side run out of Toughness or one side decides to retreat. If an army retreats, all remaining soldiers become Routed Casualties.
Aftermath phase.pngAftermath PhaseThe winning army gives chase to the defeated army and attempts to turn Routed Casualties into Fatal Casualties. When the phase ends, the defeated army moves into an adjacent Barony with all Routed Casualties and cannot be given orders until if finished traveling a couple of Baronies away, but will travel slightly faster than controlled armies.
Advantage Modifier

Once combat begins, the Advantage, a modifier that will stay the entire battle and increases the amount of damage of all troops from both sides, is calculated. Advantage comes from traits, terrain, buildings, and the Martial skill of the Commander. Each Commander will also make a roll every 3 days in an attempt to increase their Advantage, and the roll can be affected by a number of different modifiers and traits. Each point of Advantage increases an Army’s damage by +2%. Starting Advantage can be affected by the following:

  • +30% if Army is defending across a strait
  • +20% if Army is defending across a large river
  • +10% if Army is defending across a river
  • +5% if Liege is Leading the Army
  • -10% if Realm is in debt
  • -10% if Army is gathering
  • -10% if Army is low on supplies
  • -25% if Army is out of supplies
  • -30% if Army is attacking across sea

A Siege takes place once a hostile army attacks a Fortified Holding and outnumbers the Holding’s Garrison (picture of soldier next to tower icon with number 560 in picture below). Sieges will provide the main way of gaining War Score. In order to occupy a County, all Fortified Holdings have to be occupied. Castles and County Capitals are fortified by default. How difficult it is to besiege a Fortified Holding is determined by its Fort Level (Castle looking icon with the number 4 in the picture below), which can be increased by certain buildings and modifiers. The base amount of Siege Progress needed to occupy the Holding is 100, each Fort Level increase it by 50. Siege Progress is gained every tick, especially if the attacker heavily outnumbers the garrison or there are siege weapons in the army, which include Onagers or Mangonels.

Being attacked while besieging a Fortified Holding will make the besieger the attacker of the battle and giving any terrain defensive bonus to the other army instead. There is also an additional Advantage penalty for fighting in the same Barony as a Fortified Holding.

Every siege keeps track of the defenders’ supplies, average health and fortifications. During sieges, certain events can happen by default every 20 days (this is reduced to 14 days if the Commander has the Military Engineer Trait), which can lower one of those. Walls can only be damaged if the attacking army has Siege weapons like Mangonels.

LogoAssetStage 1 EffectsStage 2 EffectsStage 3 Effects
https://i0.wp.com/ck3.paradoxwikis.com/images/thumb/c/cb/Siege_action_supplies.png/90px-Siege_action_supplies.png?w=860&ssl=1Garrison SuppliesNone+10 Daily Siege Progress (One-time)+30 Daily Siege Progress (One-time)
https://i0.wp.com/ck3.paradoxwikis.com/images/thumb/e/e7/Siege_action_disease.png/90px-Siege_action_disease.png?w=860&ssl=1Garrison HealthNone+10 Daily Siege Progress (One-time)+20 Daily Siege Progress (One-time)
https://i0.wp.com/ck3.paradoxwikis.com/images/thumb/5/5f/Siege_action_walls.png/90px-Siege_action_walls.png?w=860&ssl=1WallsNone-10% Time Between Siege Events (Can Assault the Fort)-30% Time Between Siege Events (Can Assault the Fort)

Assaulting the Fort will add a large amount of daily Siege Progress, but it will be at the cost of casualties of your Army.


Once the besieging forces reach 100% siege progress, they become the controller of the Barony. IF they control all Fortified Holdings within a County, they will also occupy the entire County. Upon occupation, the County loses Control. This is of course if the original owner has the Overseer Lifestyle perk Enduring Hardships). Occupying the War Target’s holdings provides War Score.

War Score

The success of a War is measured by the War Score to determine which side is winning the War. The War Score ranges from -100% to 100%. Each point added to one side takes it away from the other side. So for example if you have 50% War Score as the attacker, the defender would have -50% War Score. War Score is gained by winning Battles, Occupying Holdings, Capturing VIP prisoners, and most importantly having control of the Casus Belli’s Objective, or War Target. Even though the game doesn’t define the term War Target, it is based on the possession of at least one County that is being fought over.

ObjectiveBonus War Score
Capturing Enemy Ruler+100
Capturing Enemy Ruler’s Heir+50 Primary Heir
+25 Secondary Heir
+10 Tertiary Heir
Occupying Enemy Capital+10

The benefits given by winning battles is based on on the size of the losing Army in relation to the percentage of total soldier count. The benefits given by Occupying Holdings corresponds to the percentage of the total holdings that defender has in their Realm. Note that the percentage allocated to winning battles is limited to 50% total, so there is no way to win a War as an attacker without also Occupying Holdings or Capturing VIP Prisoners during the battles.

At +30 War Score, the winning side can call for White Peace. At +100 War Score, the winning side can Enforce Demands on the losing side. Alternatively at -100 War Score, the losing side must surrender to the winning side. This can be modified through different perks, specifically the Peacemaker Lifestyle Perk.

Players can choose to Surrender to the opposing side at any time. This will end the War and enforce the opposing side’s demands on themselves. This can be a good tactic if you have another enemy declaring War on you and you are not able to handle both wars at the same time. The AI will also eventually surrender to the player when the player has 100 War Score, preventing the player from taking additional captives or inflicting additional damage to their Realm.

War Contribution

Wars where allies for either the attacker or defender has a percentage of War Score that is tracked by each ally’s army. When the War ends, a certain amount of Gold, Prestige or Piety is shared among all allies based on War Contribution.

If a War lasts at least 2 years and one of the allies has 0% War Contribution, the original attacker or defender will lose -20 Opinion with the War Leader that did not contribute. They will either have to pay Gold or put forward Prestige and promise to earn War Contribution within a year. Breaking this promise will result in losing a Level of Fame as well as -50 opinion with that War Leader.

Ending a War

There are only two ways that a War can end. The first is victory for one side and the other is with a White Peace. If the attacker achieves victory, they benefit from the effects of the used Casus Belli. If the defender achieves victory, the attacker is forced to pay a large sum of Gold to the defender and will lose Prestige or Piety.

White Peace can be proposed at any point by either side and requires the other side to accept it. In case of White Peace, the attacker loses a small amount of Prestige or Piety. It does not remove the use of the Casus Belli in the future.

After a War, the allies of both sides will gain Prestige regardless of the victor was, based on their Contributions.

When a War ends, the attacker will gain a Truce with the defender for 5 years. If the former attacker declares war again while the Truce is active, they will lose 250 prestige and one Level of Fame and gain -50 General Opinion for 3 years.

Offensive and Defensive Wars

An Offensive War is one where you are the attacker and have declared War on another Ruler. Usually, these are Wars that you have chosen to be part of. A defensive War is one where you are the defender. There is no Prestige cost to call an ally to assist in a defensive War. However there is a cost for offensive Wars that is based on the ally’s rank:

RankPrestige Cost

After 6 months have passed since the start of a War, the attacker in an offensive War will start to gain negative Opinion with all Vassals. Every two months after that their Opinion will decrease by -1. After the War is over, the penalty will decay at the same speed. Civil Wars, defensive Wars, and Great Holy Wars do not cause Opinion loss. Faiths that have the Warmonger tenet also do not suffer this penalty.