Land warfare

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Land combat in Imperator occurs when at least two armies of states currently at war with each other are in the same city. The army that entered the city first is considered the defender, unless the other side has control over fortifications in the province.

On each side, more than 1 army can partake in combat. The simplest way to achieve this is by attaching armies to a leading army. Armies may be attached to allied armies or to the state's own.

Combat[edit]

Battle chess board[edit]

In Imperator: Rome, the battle chess board is divided into squares, grouped into 2 rows with 30 squares each. Each side has a single row. One cohort fills one square.

Rows have a main front on the middle and flanks on the sides. On the initial deployment the main front is filled with expensive units such as War Elephants, Heavy Cavalry and Heavy Infantry.

Flanks are deployed with mobile units such as Horse Archers, Camel Cavalry and Light Cavalry. These units have a high maneuver which allows them to target units in the center after defeating their opponent.

When units get eliminated they get reinforced by cheap units such as Chariots, Archers and Light Infantry.

How the player can affect deployment[edit]

Besides deciding the composition of the army, the player can additionally affect the deployment of troops on the Battle chess board in the following ways:

  • Primary unit: Gives this unit type the highest priority when deploying the main front.
  • Secondary unit: Gives this unit type the highest priority when reinforcing the main front.
  • Flank unit: Gives this unit type the highest priority when filling flanks.
  • The minimum size of both flanks (2, 5 or 10 cohorts)

The default selected choices will depend on the Military Traditions but they can be changed at no cost at any time.

Battle[edit]

Each day, each cohort in the first battle row of each side will attack another within its range. A unit type's range in squares is equal to its maneuver value.

The opposing cohorts inflict strength-damage and morale-damage.

Casualties and morale depletion are applied at the end of each day to each cohort taking part in the battle. The Attacker-role and Defender-role are calculated the the same way, but may be subject to some modifiers.

Each cohort has separate base values for strength-damage and morale-damage. These are subject to a random dice roll every 5 days and by other modifiers.

At the end of each day units with less than 0.25 Morale disengage until the end of the battle. On the next day, other units or reserves fill in the ranks to take their place. The day after the last available unit from either side disengages, combat ends and the defeated army is forced into a shattered retreat.
Unlike some other games (e.g. CK2), there is no pursuit phase where the victors run down and inflict heavy casualties upon the broken forces.

Ordered retreat[edit]

After 5 days of combat have passed, it becomes possible to order a retreat by ordering an army to move to another city. At that point the battle is considered lost with corresponding reduction of the warscore and losses to the general's popularity.

Each army in a combat engagement can be separately ordered to retreat by selecting it from the outliner. Any remaining armies continue fighting and deploying reserves to fill in abandoned positions.

Because of this possibility it might prove advantageous to group Unit archers.png (+25% morale damage) or Unit light infantry.png (-25% morale damage) into armies of their own and have them retreat prematurely.

Tips: Largest impact[edit]

In summary, the variables that impact the combat the most are:

  • For morale damage - current morale. A unit at full morale does 5x morale damage of a unit that is on low maintenance.
  • With small armies - flanking/maneuver. Flanking with 5 horse archers on each side makes enemy side units take 6x damage, while horse archers themselves stay at full morale and manpower.
  • General skill and terrain. A 5 pip advantage (e.g. 10 skill general vs 1 skill general) gives +100% base damage.
  • Heavily countering unit types. E.g. Light Cavalry vs Heavy Infantry does only 50% normal damage.
  • Low manpower. A battered non-consolidated 500-man cohort will only do 50% of the damage of a full 1000-man cohort, while still taking a full space on the front line.

Siege[edit]

Assault – when an army besieges a city with a fortress building, the player can order an assault; only infantry (including archers) participates in an assault

Effect on Warscore[edit]

Main article: warscore

Won and lost battles affect the warscore, and so do the number of casualties inflicted and received.

Effect on General's Popularity[edit]

Won and lost battles affect the Popularity popularity of the character hired as army leader.

Modifiers[edit]

(see concept: modifiers)

Leader modifiers[edit]

The Military power.png martial skill of the characters hired as army leaders are compared, with every 2 levels difference giving a +1 bonus to the army of the better general.

Terrain modifiers[edit]

Main article: Terrain types

The attacker receives one or more penalties depending on the city's terrain and map features.
The defender never suffers terrain penalties.
The value can only be zero or less, it cannot be positive.

  • Hills, Marsh and Forests give -1 to the attacker
  • Mountains give -2 to the attacker

The following penalties stack on top of any terrain effect:

  • Crossing a river -1
  • Attempting a naval landing -2
  • Crossing a strait -2

Thus the maximum possible penalty is -4 (E.G. a naval landing into mountains).

Discipline[edit]

Discipline.png Discipline is a generalized summary of various modifiers to damage done or received in battle. It exists as an overview to aid players. Discipline itself is a value that serves solely as a modifier, and then other modifiers may adjust the discipline value further. It is calculated on a state level per unit type. When pressing the military button in the top bar, it is possible to see the current modifiers for all unit types.

A unit's final discipline value is determined by a combination of factors including:
The Military power.png martial skill of the character holding the state's "Military tribune" position, some Inventions, some trade goods, the Blessing of Mars, and many other factors.

In a strange exception to this rule, combat tooltip seems to calculate +10% improved discipline from Personal Loyalty to a general twice: both multiplicative and additive. E.g. with +15% country Light Cavalry discipline, a loyal cohort shows +26.5%. The difference of 1.5% is small enough that it's difficult to tell if the tooltip is wrong, or if it's actually calculated this way.

Experience[edit]

Every unit accumulates experience when a battle ends. Experience gives ~0.3 damage reduction per 1% of experience. So a unit with 100% experience will receive ~30% less damage. Recovering manpower decays unit's experience with 50% efficiency.

experience = previous_experience * (1 - recovered_manpower / previous_manpower * (0.5 - reduced_experience_decay))

Archers have a slightly increased damage reduction because of extra morale damage taken. Similarly Heavy Infantry, Light Infantry and War Elephants have a slightly decreased damage reduction.

Combat tactics[edit]

The available combat tactics add a rock-paper-scissors-Spock-lizard-mechanic to battles, i.e. each tactic is strong against two other tactics, and poor against two more.

  • The modifier applies to the damage done.
  • The positive modifier applies only to certain unit types, i.e. the displayed "total effectiveness" of a tactic is determined by the army's composition.
  • The negative modifier applies fully regardless of army's composition.
  • Casualties modifier applies to both armies.
  • For each army a combat tactic is chosen from the available ones.
  • The default is "Shock Action".
  • The combat tactic can be changed at any time prior to a battle at no cost.

The effect of any specific tactic is not overwhelmingly powerful. See ##Tips:_Largest_impact to compare the magnitude of other combat modifiers.

General tactics[edit]

These five tactics are available to all states.

Tactic Unit effectiveness Against other tactics Casualties Description
Bottleneck Bottleneck
  • Unit archers.png Archers: 50%
  • Unit cavalry.png Heavy Cavalry: 80%
  • Unit heavy infantry.png Heavy Infantry: 100%
  • Unit light infantry.png Light Infantry: 25%
  • Shock action Shock Action: +20%
  • Hit-and-Run Hit-and-Run: +20%
  • Skirmishing Skirmishing: −10%
  • Cavalry skirmish Cavalry Skirmish: −10%
Against a massed charge, nothing performs better than a solid defensive line. However, if the enemy is clever enough to pick us off one by one, we may encounter problems.


Deception Deception
  • Unit camel cavalry.png Camel Cavalry: 100%
  • Unit chariots.png Chariots: 100%
  • Unit horse archers.png Horse Archers: 150%
  • Unit light cavalry.png Light Cavalry: 150%
  • Skirmishing Skirmishing: +20%
  • Triplex acies Triplex Acies: +20%
  • Envelopment Envelopment: −10%
  • Hit-and-Run Hit-and-Run: −10%
A staggered assault can wear down an enemy's resolve faster than one might imagine, and allows us to respond to mobile threats with great ease. The greatest weakness of this tactic stems from our vulnerability to skirmishing behavior.


Envelopment Envelopment
  • Unit camel cavalry.png Camel Cavalry: 100%
  • Unit chariots.png Chariots: 50%
  • Unit cavalry.png Heavy Cavalry: 50%
  • Unit horse archers.png Horse Archers: 50%
  • Unit light cavalry.png Light Cavalry: 100%
  • Deception Deception: +20%
  • Phalanx Phalanx: +20%
  • Shock action Shock Action: −10%
  • Padma vyuha Padma Vyuha: −10%
Drawing forth an enemy counterattack, and then plunging into the side of their exposed formation can cause massive losses. Against an enemy who can quickly martial their men to multiple fronts however, increases the risk of this maneuver.


Shock action Shock Action
  • Unit cavalry.png Heavy Cavalry: 100%
  • Unit heavy infantry.png Heavy Infantry: 100%
  • Unit war elephants.png War Elephants: 200%
  • Envelopment Envelopment: +20%
  • Padma vyuha Padma Vyuha: +20%
  • Bottleneck Bottleneck: −10%
  • Phalanx Phalanx: −10%
+10% Sometimes, caution must be thrown to the wind - few foes can stand against a massed charge, though we must be wary of those that can field a staunch defense.

This is the default tactic for any new army


Skirmishing Skirmishing
  • Unit archers.png Archers: 50%
  • Unit camel cavalry.png Camel Cavalry: 25%
  • Unit horse archers.png Horse Archers: 25%
  • Unit light cavalry.png Light Cavalry: 25%
  • Unit light infantry.png Light Infantry: 100%
  • Bottleneck Bottleneck: +20%
  • Cavalry skirmish Cavalry Skirmish: +20%
  • Deception Deception: −10%
  • Triplex acies Triplex Acies: −10%
−25% If the enemy exposes a series of flanks for us to harry, this maneuver will surely pay off. We should not employ this tactic against stalwart offensive lines, however.

Specialized tactics[edit]

These other tactics are only unlocked by specific military traditions.

Tactic Unit effectiveness Against other tactics Casualties Description
Cavalry skirmish Cavalry Skirmish
  • Unit camel cavalry.png Camel Cavalry: 50%
  • Unit cavalry.png Heavy Cavalry: 50%
  • Unit horse archers.png Horse Archers: 150%
  • Unit light cavalry.png Light Cavalry: 150%
  • Bottleneck Bottleneck: +25%
  • Padma vyuha Padma Vyuha: +25%
  • Skirmishing Skirmishing: −10%
  • Phalanx Phalanx: −10%
−10% Ordering cavalry to harass and skirmish, rather than remain in formation, can often be used as a tool to deny an entire flank to hostile troops.

Requires Greek war tradition "The Companion Cavalry", North African war tradition "Wild Charge", or Persian war tradition "Cavalry Skirmish".

Hit-and-Run Hit-and-Run
  • Unit archers.png Archers: 50%
  • Unit camel cavalry.png Camel Cavalry: 50%
  • Unit chariots.png Chariots: 50%
  • Unit horse archers.png Horse Archers: 100%
  • Unit light cavalry.png Light Cavalry: 100%
  • Unit light infantry.png Light Infantry: 100%
  • Deception Deception: +25%
  • Triplex acies Triplex Acies: +25%
  • Bottleneck Bottleneck: −10%
  • Padma vyuha Padma Vyuha: −10%
−10% In the face of an overwhelming enemy an asymmetric approach can often be more successful than a head-on one. Ambushes, raids, and hit-and-run style tactics were common in ancient warfare, especially in Gaul, Germania, and Iberia

Requires Barbarian war tradition "Ambush".

Padma vyuha Padma Vyuha
  • Unit archers.png Archers: 100%
  • Unit chariots.png Chariots: 50%
  • Unit heavy infantry.png Heavy Infantry: 75%
  • Unit light cavalry.png Light Cavalry: 50%
  • Unit war elephants.png War Elephants: 100%
  • Envelopment Envelopment: +25%
  • Hit-and-Run Hit-and-Run: +25%
  • Shock action Shock Action: −10%
  • Cavalry skirmish Cavalry Skirmish: −10%
−10% A highly complex defensive formation, the labyrinthine appearance of the Padma Vyuha is designed to confuse and misdirect foes while defending more vulnerable friendly troops at the core.

Requires Indian war tradition "Padma Vyuha".

Phalanx Phalanx
  • Unit war elephants.png War Elephants: 100%
  • Unit heavy infantry.png Heavy Infantry: 100%
  • Unit light cavalry.png Light Cavalry: 75%
  • Unit light infantry.png Light Infantry: 75%
  • Shock action Shock Action: +25%
  • Cavalry skirmish Cavalry Skirmish: +25%
  • Envelopment Envelopment: −10%
  • Triplex acies Triplex Acies: −10%
−10% The Phalanx originated as a highly defensive method of formation fighting, used primarily by Greek city-states. It was further developed by the Macedonian military, who built their armies around a heavily armored Phalanx formation.

Requires Greek war traditions, or Levantine and Arabian war tradition "Greek Warfare".

Triplex acies Triplex Acies
  • Unit heavy infantry.png Heavy Infantry: 100%
  • Unit light cavalry.png Light Cavalry: 60%
  • Unit light infantry.png Light Infantry: 100%
  • Skirmishing Skirmishing: +25%
  • Phalanx Phalanx: +25%
  • Deception Deception: −10%
  • Hit-and-Run Hit-and-Run: −10%
Like the Hellenistic Phalanx the Roman tactic formation known as the Triplex Acies, or triple lines, is inspired by the Phalanx of the Greek City states. Where the Macedonian or Hellenistic Phalanx has gone for cohesion the Roman Formation instead emphasized flexibility.

Requires Latin war tradition "Triplex Acies".

Damage formula[edit]

Example damage tooltip. Note: "Morale: +26.00%" is incorrect and should read "x0.26"

The damage formula is mostly explained in-game on the damage tooltip. The tooltip is split to 5 sections.

Unit information[edit]

  • Unit type: The tooltip uses the common name of the typ when the modifier is based on the unit's type.
  • Unit name: The tooltip uses the unit's name when the modifier is based on the unit's attributes.
  • Unit strength: Multiplier for all damage dealt.
  • Unit morale: Multiplier for morale damage dealt.

Inflicted losses[edit]

This sections shows losses that this unit will cause to the target unit in the next round. The text is misleading indicating these losses were caused this round. However the values use the current strength and morale of the unit, not values in the previous round.

Base damage[edit]

  • Dice roll: Random value between 1 and 6 is rolled every 5 days for each side.
  • Terrain & Leader modifiers: Added to the dice roll. Terrain modifier causes up to -4 penalty to attacker. General causes up to 7 bonus to the side with a better general (skill difference / 2). (#Terrain_modifiers, #Leader_modifiers)
  • Base damage: Base damage caused by a single unit.
 pips = dice_roll + terrain_penalty + leader_bonus
 base_damage = 0.08 + (0.02 × pips)

Total damage[edit]

Base damage is multiplied by several values to calculate the total damage caused by a single unit.

  • Discipline: Increases caused damage in all combat situations. Main sources are military traditions, trade and loyalty. Usually from 0% to +40%. (#Discipline)
  • Terrain bonus: Unit type may cause increased damage in the current terrain. Main source is military traditions. Usually from 0% to +15%.
  • Vs Defender: Unit type may cause increased or reduced damage against the opposing unit type. From -50% to +50%. (Unit Types)
  • Tactic vs Tactic: Selected tactic may cause increased or reduced damage against opponent's tactics. Amount of the increased damage depends on unit types in the battlefield. From -10% to +25%. (#Combat_Tactics)
  • Attacker Offense vs Defender Defense: Units may cause increased damage or receive reduced damage. Main sources are military traditions and trade. Usually from -15% to +30%.
  • Defender Experience: Unit's experience reduces received damage. From 0% to -37.5%. #Experience
 experience_reduction = 0.003 * VS_experience * (morale_damage_taken + strength_damage_taken) / 2
 total_damage = base_damage × (1 + discipline) × (1 + terrain_bonus) × (1 + VS_unit_type) × (1 + tactics_mod) × (1 + offense - defense) × (1 - experience_reduction)

Strength and morale damage[edit]

Total damage gets multiplied by strength of the unit and then further modified by strength and morale specific multipliers.

  • Damage from: Should show total damage from the attacker. Currently always shows 0.
  • Casualties from Tactics: Some tactics increase or decrease strength damage for both attacker and defender. From -50% to +20%. (#Combat_Tactics)
  • Daily Multiplier: Multiplier (0.2x) for strength damage.
  • Defender: Some unit types receive increased or reduced strength damage. From -50% to 0%. (Unit Types)
  • Morale: Attacker's own morale directly affects caused morale damage. Tooltip shows wrong value (should be reduced by 100%, for example +26.00% should be -74.00%). Usually from -75% to 200%.
  • Daily Multiplier: Multiplier (1.5x) for morale damage.
  • Defender: Some unit types receive increased or reduced morale damage. From -25% to +25%. (Unit Types)
 strength_damage = total_damage × current_strength × (1 + casualties_from_tactics) × 0.2 × (1 + VS_unit_type)
 morale_damage = total_damage × (current_strength ÷ 1000) × (current_morale ÷ 2) × 1.5 × (1 + VS_unit_type)

One notable difference from EU4 is that current, not maximum morale, is used to determine morale-damage; so worn down units inflict much less morale-damage on the enemy. Also units that are flanking or in reserve do not suffer any morale hits.

On average you can expect to roll (1+6)/2 = 3.5 and with equal generals and no terrain penalties have a base-damage of 0.8 + 0.2*3.5 = 0.15. In the absence of other modifiers this corresponds to 1000-man cohort with 3.0 morale killing 0.15*1000*0.2 = 30 men and inflicting 0.15*1*(3/2)*1.5 = 0.33 morale damage per day.

Each pip modifies base-damage by 13% of this expected average.
The worst possible base-damage is 0.02, having -4 from terrain and rolling a 1 with an equal or worse general. The best possible is 0.34, rolling a 6 with +7 from general (14-skill general vs no general) and no terrain penalty.

Deployment and reinforcement[edit]

All units are priorized based on unit type and location in the army screen. Unit type has the biggest impact while the location is used to resolve ties.

Default priorities for unit types are:

  • Main front group (units with less than 3 maneuever, ordered by build cost): War Elephants, Heavy Cavalry, Heavy Infantry, Chariots, Archers/Light Infantry
  • Flanks group (units with more than 2 maneuver, ordered by maneuver): Horse Archers, Camel Cavalry, Light Cavalry

Preferred unit types modify these priorities:

  • Primary unit: Moves the unit type to front of the Main front group.
  • Secondary unit: Moves the unit type to end of the Main front group.
  • Flank unit: Moves the unit type to front of the Flanks group.


Phase Part Main priority Back up
Initial deployment Main front Main front group Flanks group
Initial deployment Flanks Flanks group Main front group
Reinforcement Main front Reversed Main front group Reversed Flanks group
Reinforcement Flanks Reversed Main front group Reversed Flanks group

The flank size is the highest of:

  • The preferred flank size (only works with more than 32 units)
  • Amount of free space the enemy has on the board

Left and right flanks can have different sizes.


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