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A 3 vs 3 flanks battle

Combat.png Combat occurs when two hostile armies arrive on the same province.

Reference: Combat mechanics thread


In a battle, each side has up to three flanks:

  • Left flank
  • Center flank
  • Right flank

These flanks will generally fight separately against the same flank on the opponent's side. Each flank has a commander, and its own units. To have more than one flank you need multiple armies, though they can be merged into one.

When a flank no longer has an equivalent flank to attack, it will help another flank instead. It will now also get a flanking bonus of 30%, meaning it does 30% more morale and troop damage. The enemy flank will now be under attack from two flanks, thus taking much more damage.


Combat is divided into three phases:

  1. Skirmish.png Skirmish: All battles will start in the Skirmish phase. This is when archers and horse archers excel, and they will be the only ones doing any major damage.
  2. Melee.png Melee: After a few days, it will switch to the Melee phase, where melee oriented units like heavy infantry and pikemen excel. Note that flanks do not necessarily have to be in the same phase as each other, and they'll usually enter Melee at slightly different times.
  3. Pursue.png Pursue: When the morale of a flank reaches 25%, they will start retreating, and combat will switch to the Pursue phase. This is where light cavalry truly excels, but heavier cavalry does well also.

Retreat.png Retreat: After 5 days, the flank will be removed from combat:

Unit Attack and Defense[edit]

The formula for finding out the attack or defense of a unit is:

(Base unit stat) * (1 + tech bonus + terrain bonus + cultural bonus + tactic bonus) * (1 + leader trait bonus + tactical affinity bonus).

Unit Statistics[edit]

Base unit stat depends on the type of unit and the phase:

Attack Defense
Morale Maintenance Skirmish Melee Pursue Skirmish Melee Pursue
Light infantry.png Light Infantry (LI) 2 0.7 1 1 2 2 1 2.5
Heavy infantry.png Heavy Infantry (HI) 4 3 0.25 6 1 3 4 4
Pikemen.png Pikemen (P) 6 2 0.1 5 0.2 3.5 4.5 2
Light cavalry.png Light Cavalry (LC) 4 3 2 3 6 4.5 3 4.5
Heavy cavalry.png Heavy Cavalry (HC) 10 6 0.5 10 4 4 5 7.5
Archers.png Archers (A) 1 2 2 1 2 1.5 1.5 2.25
Horse archers.png Horse Archers (ST) 3 4 4 1 7 4.5 2 4.5
War elephants.png War Elephants (ST) 15 20 0.25 25 3 6 10 3
Camel cavalry.png Camel Cavalry (ST) 5 3 3 6 3 2 2 1.5
Ships.png Ships - 300 - - - - - -

ST = Special Troops (varies with region/culture)

Military Technology[edit]

Main article: Technology

Tech bonus depends on military technology level: +0%/+10%/+15%/+20%/+25%/+30%, depending on the relevant tech level.

  • for a unit raised from a specific holding, it is the tech level in that county that matters.
  • for a unit raised from a vassal, it's the vassal's average tech level.
  • for a retinue unit, it's your capital's tech level.


Terrain defines the surroundings where battles are fought. The defenders usually have the advantage and terrain can play a vital role in a fight.

The following terrain give a terrain bonus to the defender:

  • Hills
  • Mountain

The following elements between two provinces give a terrain penalty to the attacker:

  • Rivers and Strait. To see if there is a river or strait between two provinces, select one of them and look for the icon RiversStraitsIcon.png.
  • Major river: twice the penalties of crossing a normal river
  • Amphibious landing: almost identical to a strait crossing. Note: if you control at least one holding in a county, you can have your ship land in the county. Your soldiers will be off-loaded and fight any enemies there without the amphibious landing modifier.

There are also several other terrain types which don't give a bonus or penalty to either side of a battle, though they can negatively affect the supply limit (especially true for deserts) - attrition has won many wars.

Mountain defense.png Hill defense Mountain defense.png Mountain defense River crossing.png River crossing Strait crossing.png Strait crossing Amphibious landing.png Amphibious landing
Attack Defense Attack Defense Attack Defense Attack Defense Attack Defense
Light infantry.png Light Infantry +10% -10% -10% -15% -15% -15% -15%
Heavy infantry.png Heavy Infantry +10% -15% -15% -20% -20% -20% -20%
Pikemen.png Pikemen +10% +5% +20% +10% -15% -15% -20% -20% -20% -20%
Light cavalry.png Light Cavalry -12.5% -12.5% -17.2% -17.2% -17.5% -17.5%
Heavy cavalry.png Heavy Cavalry -15% -15% -20% -20% -20% -20%
Archers.png Archers +20% +15% +30% +20% -10% -5% -15% -10% -10% -15%
Horse archers.png Horse Archers +15% +10% +25% +15% -12.5% -7.5% -17.2% -12.5% -12.5% -17.5%

Patch 2.0 introduced a new system of terrain bottlenecks. "This is a system where the defending side in a battle has sometimes found suitable terrain before combat commences. The chance of this depends on the main province terrain and leader skill (there is even a new commander trait for this.) Each flank may have a narrow approach, preventing the attackers from attacking in numbers greater than the number of flank defenders (their number at the start) during the melee phase."

Cultural Building[edit]

Main article: Cultural Buildings

Cultural buildings can provide a cultural bonus to units trained in that holding. All cultural buildings are 4-leveled, with each level providing an equivalent boost to some unit. Note that this only applies to troops trained in the relevant holding

Retinues used to have no home holding, but automatically got a benefit equivalent to that provided by the level-4 cultural building, however this has since been changed to instead use the bonus of the current level of cultural building in your capital.

Combat Tactics[edit]

Main article: Combat tactics

Tactic bonus ranges from -150% to +420%. Note that these are so huge, they often swamp technology-based and terrain-based modifiers. Tactical affinity bonus ranges from -120% to +300%.

Leader Traits[edit]

Main article: Commander

Every army can have up to three commanders, one per flank. The skill of the general allows to choose more advanced tactics, which will also increase his troops' effectiveness.

Any adult character who has been educated in the martial attribute is given certain leader trait bonus - the specific bonuses of each martially-trained character are visible underneath their list of traits on their Character screen. All the values are scaled by leader martial skill.

Name Command ID Units Casualty and morale Terrain Other modifiers Combat Tactics Cost
Light foot leader.png Light Foot Leader light_foot_leader 102 +20% Light Foot Troops 0
Heavy infantry leader.png Heavy Infantry Leader heavy_infantry_leader 103 +20% Heavy Foot Troops 0
Cavalry leader.png Cavalry Leader cavalry_leader 104 +20% Mounted Troops Heroic Countercharge 0
Inspiring leader.png Inspiring Leader inspiring_leader 105 +15% Morale Damage
+15% Morale Defence
Inspired Defense
Religious Fervour
Trickster.png Trickster trickster 106 +30% Experimentality Clever Ambush 0
Organizer.png Organizer organizer 107 +20% Movement Speed
+10% Retreat
Timid Advance 0
Defensive leader.png Defender defensive_leader 108 -10% Damage
+25% Defence
Inspired Defense 13
Experimenter.png Direct Leader experimenter 109 +20% Leading the Center 0
Flanker.png Flanker flanker 110 +20% Flanker 0
Aggressive leader.png Aggressive Leader aggressive_leader 111 +10% Damage
-10% Defence
+25% Persuit Heroic Countercharge
Reckless Charge
Siege leader.png Siege Leader siege_leader 112 +40% Siege 0
Flat terrain leader.png Flat Terrain Expert flat_terrain_leader 126 +20% Plains
+20% Farmlands
+20% Steppe
Rough terrain leader.png Rough Terrain Expert rough_terrain_leader 127 +20% Forest
+20% Hills
Mountain terrain leader.png Mountain Expert mountain_terrain_leader 128 +20% Mountains 0
Desert terrain leader.png Desert Expert desert_terrain_leader 129 +20% Desert 0
Holy warrior.png Holy Warrior holy_Warrior 130 +30% Damage Against Religious Enemies 0
Unyielding leader.png Unyielding unyielding_leader 131 +10 Defence
+20% Morale Defence
Narrow flank leader.png Battlefield Terrain Master narrow_flank_leader 158 +50% Narrow Flank 0
War elephant leader.png War Elephant Leader war_elephant_leader 174 +20% War Elephants +20% Morale Damage 10
Jungle terrain leader.png Jungle Expert jungle_terrain_leader 174 +20% Jungle 0
Winter soldier.png Winter Soldier winter_soldier 177 +4 Winter Supply
+50% Winter Combat


Every day each soldier from a flank will take a swing at the enemy, causing damage based on its attack value. All damages for the flank are added together and sent to the flank that's being attacked. The defense of the receiving units is computed, and RIP.png casualties are inflicted as:

TROOP_KILL_FACTOR * (damage received / unit defense).
TROOP_KILL_FACTOR is defined in defines.lua as 0.015.

In addition each soldier who dies does 3 morale damage to the survivors (MORALELOSS_FACTOR).

The survivors have morale points equal to the sum of their morale values, so if they take 60 morale damage but the survivors have 6000 morale points then morale will be down by 1%. This means that RIP.png deaths are a double penalty, both reducing the number of morale points a flank has, and reducing the number of soldiers.

Note that the calculations happen simultaneously every day for every flank involved in the battle, so all values will be calculated based on the number of troops present before anyone dies. Do note that in the Pursue phase the fleeing flank will not make any attacks.

Combat ends once all flanks on one side are either dead or have fled. Flanks attempt to flee once their morale hits 20% or they're manually withdrawn from combat. Flight takes four days.

Prestige and piety[edit]

Each battle results in 1 prestige for every 100 losses of the losing army. A portion of this prestige goes to the characters involved:

  • 50% goes to the owners of the units (divided among them)
  • 25% goes to the main Commander of the centre
  • 12.5% goes to each flank Commander

In addition for every 1 prestige gained, characters will gain 1.5 piety if fighting religious enemies.


See Combat mechanics thread for detailed insight on possible strategies.

Upgrade and specialize your holdings: combat tactics will, during combat, temporarily make some units incredibly powerful and others basically useless. For example, an army doing Swarm will temporarily have quadruple horse-archer damage and no damage from archers and light cavalry. So specialization is the name of the game.

Make it all your unique retinue unit: by using retinue alone in a flank it allows to select combat tactics that are particularly beneficial due to there being just one or two unit types in the whole flank; they also will benefit from the cultural unit bonus.

Flank composition: the Rule of Two: In order to maximize combat tactics efficiency, a flank should contain no more than two of the three major skirmish units (Horse Archers, Archers, Light Cavalry), and no more than two of the three major melee units (heavy infantry, pikes, and knights).

Bait enemies into attacking fortified positions: Ideally, your army is on a mountain, and across a major river from the attacker.

Avoid attacking across rivers and into hills: you'll get a moderate combat penalty, which could make a major difference. These penalties don't matter much if you outnumber the enemy by a lot, though.

Order early retreats when losing a battle. Simply order your army to move to another province, and it will begin retreating regardless of morale.

Scout and match. Send a tiny army to determine the strengths of your opponent's flanks. Then rearrange your main army to have two "holding" flanks, evenly matched against the opponent, and one "breakthrough" flank, with extra troops and your best offensive commander.

CombatCombat tacticsCommandersRaiding