Land combat in Imperator occurs when at least two armies of states currently at war (or otherwise hostile) with each other are in the same territory, and forms one of the main pillars of warfare in the game. Once engaged in battle, both sides will fight and deal damage to each other's strength and morale until one side is either forced to retreat or completely destroyed. The outcome of a battle depends on many factors, including the strength and morale of each army, their composition, commander martial and ability, the local terrain, modifiers such as discipline and experience, pure luck, and more.
Victorious armies accrue warscore, inflict greater losses, and deny the enemy the ability to besiege and occupy friendly territory (or interrupt sieges and occupation of enemy territory). Typically, the side that can more consistently win battles and inflict proportionally greater losses on the enemy will emerge victorious in the war.
Initiating a battle[edit | edit source]
A battle begins when two armies when two armies that are hostile to each other - typically because they belong to countries that are at war, but also including circumstances such as a country's armies engaging invading barbarian hordes - are in the same territory. If there are multiple armies in the territory that have the same owner, are on the same side of a war, or are at least co-belligerent with a hostile army that they are engaging with, they will be considered on the same side of the battle, and will fight together in the battle as though they were a single army. This is particularly relevant when fighting in an alliance where multiple allied armies need to join together to engage the enemy armies, or for larger countries with multiple levy and legion armies that cannot be merged together. Attaching armies to a leading allied or owned armies, which will make the attached army following the leader as closely as possible (though this may not work perfectly if the two armies have a different movement speed), can be a helpful aid in this.
In the rare event that there are three hostile sides with armies in the same territory, the first two sides to arrive will engage first, ignoring the third side. Once that battle is over, the side that won the first battle will immediately engage the third side in a new battle, while the defeated side retreats.
Imminent battle[edit | edit source]
When there is an imminent battle that involves one of the country's armies - that is, there is an owned, allied, or enemy army that is currently moving into a territory where a battle will start assuming that it (as well as all the other nearby armies) is not given a new order - an alert will appear on the map indicating the imminent battle, as well as the estimated outcome of the battle given the circumstances and the relative strength of the potentially involved armies. The estimated outcome will give one out of five possible predictions:
- Clear win - The country's side is heavily favoured and will very likely win.
- Probable win - The country's side is favoured and will probably win.
- Undecided - Both sides are approximately evenly matched and the outcome is uncertain.
- Probable loss - The country's side is disfavoured and will probably lose.
- Clear loss - The country's side is heavily disfavoured and will very likely lose.
Note that while the imminent battle alert takes into account all armies that are currently in or moving into the territory, it does not take into account any other nearby armies that are not currently moving into the territory but are close enough to realistically intervene. For instance, if the enemy has a large army in the area that might join the battle, engaging could be more risky than the alert indicates.
Combat[edit | edit source]
Battle chess board[edit | edit source]
In Imperator: Rome, the battle chess board is divided into squares, grouped into 2 rows, one for each side. The width of the rows depends on the territory's combat width, with a base value ranging from 16 to 40 depending on the territory's terrain type that can be reduced by permanent, pre-placed gate and mountain pass territory modifiers as well as Earthworks buildings that can be built in cities. One cohort fills one square, so the combat width of the territory controls how many cohorts can actually engage at a given time. If one of the armies has more cohorts than can fit into the combat width, then they will have to wait in reserve, unable to participate in battle unless a spot opens up (from a cohort breaking and retreating or being destroyed); this means that battles in territories with a smaller combat width will have more limited opportunities for flanking and somewhat blunt the advantages of having a larger army.
Deployment[edit | edit source]
- Main article: Deployment
At the start of a battle, cohorts from both armies deploy on the battlefield. Deployment may also happen during the battle when cohorts retreat and are replaced by reserves or new armies join the battle (often referred as reinforcement).
The order and layout of deployment can be customized for each army by selecting preferred unit types and flank sizes in the army interface.
Morale[edit | edit source]
Morale represents the willingness of an army's soldiers to fight. Every cohort in an army has an individual morale value, which can range from 0 to a base maximum of 3 (adjusted by the Morale of Armies modifier), which is then averaged over all the cohorts to give the army's overall morale. Levies are raised at full morale, but legions and mercenaries start at 0 morale when raised and will take some time before they are ready for battle. If a cohort has less than its maximum possible morale, it will gain a certain percentage of its maximum morale each month based on its Army Morale Recovery modifier. The army morale recovery modifier is highly dependent on the ruler's martial skill which can be problematic for countries with a low martial, but can be increased at the cost of higher maintenance with the Unit Reorganization unit ability.
When in battle, cohorts inflict damage to both morale and strength. Cohorts that lose all of their morale withdraw from the battle and will no longer fight, and if all of an army's cohorts have lost their morale it will be forced to concede the battle and retreat. Most battles are decided by which army loses all its morale and retreats first; it is rare for an army or cohort to fight all the way to the point of annihilation unless it is already weak or is completely overwhelmed. This can allow an army to emerge victorious over another army that is larger or nominally stronger if it has higher morale or is otherwise more effective at inflicting morale damage, and can be particularly decisive in the early game.
Battle[edit | edit source]
- Main article: Damage formula
Each day, each cohort in the first battle row of each side will attack one other cohort within its range. A unit type's range in squares is equal to its maneuver value, and the opposing cohorts inflict damage to both each other's strength and morale.
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 from 1-6 every 5 days, which is then combined by a large variety of other modifiers to determine how much damage each cohort gives and takes. Because of this chance element, the exact outcome of every battle is to some extent unpredictable, though there is a limit to how much impact luck can have (if the difference in power is large enough, the stronger army will always triumph over the weaker one).
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, unless it has been completely destroyed. There is no pursuit phase where the victors run down and inflict heavy casualties upon the broken forces - once an army or cohort has retreated, it will no longer take any losses (unless the entire army is subsequently overrun).
Ordered retreat[edit | edit source]
After a few days of combat have passed, it becomes possible to order a retreat by either ordering an army to move to another territory or using the order full retreat unit ability. At that point, the battle is considered lost with a corresponding loss of warscore and commander popularity. Ordering the army to move will force it to retreat to that territory - even if it is very far away (but still accessible) - while using the order full retreat unit ability will cause the army retreat to an automatically chosen location (similar to if it was forced to retreat from lack of morale) and will additionally cause the retreating army to lose 50% of its current strength. This harsh penalty means that ordering a full retreat should generally only be used if a normal retreat is not possible, and the alternative is the complete annihilation of the army.
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 archers (+25% morale damage) or light infantry (-25% morale damage) into armies of their own and have them retreat prematurely.
The base number of days before a retreat can be ordered is 5, which can be reduced by the Retreat Delay modifier (given by the Tactical Withdrawal martial invention and wonders with the Retaliation Procedures effect) to a capped minimum of 1 day.
Stack wiping[edit | edit source]
Stack wiping means that one side of a battle gets totally wiped out, losing all of its men. This usually happens when one side is much stronger than the other. The exact rules are:
- Total manpower is greater than 10x of the enemy manpower. This is checked at start and also at end of the battle.
- Enemy can't deploy any cohorts. This happens when all cohorts have less than 0.25 morale.
- Enemy is defeated before retreat is possible and total manpower is greater than 2x of the enemy manpower.
If both sides would stack wipe then only the defender stack wipes.
Tips: Largest impact[edit | edit source]
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. 11 skill general vs 1 skill general) can increase the base damage by as much as 100%, while harsh terrain can reduce an attacker's damage by as much as 80%.
- Heavily countering unit types. E.g. Light Cavalry vs Heavy Infantry does only 50% normal damage.
- Low manpower. A battered non-consolidated 250-man cohort will only do 50% of the damage of a full 500-man cohort, while still taking a full space on the front line.
Damage modifiers[edit | edit source]
- Main article: Damage formula
In addition to the random dice roll for each side, there are a large number of modifiers that affect the damage that each cohort inflicts and takes in battle. Modifiers that affect the dice roll itself generally combine additively, while modifiers that modify damage generally combine multiplicatively. In general, most of these multipliers can be simply thought of as increasing or decreasing a cohort's effectiveness in battle, with the distinctions between these modifiers being largely about which cohorts and circumstances they are applicable in and how a country or army can acquire them.
Commander martial[edit | edit source]
During a battle, the army with the higher martial commander gets a +1 bonus to the dice roll for every 2 points of difference in martial skill, rounded down. If the difference is less than 2 or the two commanders have the same martial, then there is no bonus (or penalty) for either side.
Terrain modifiers[edit | edit source]
- Main article: Terrain types
When engaging in battle, certain terrain types and features are favourable for the defender and give penalties for the attacker. This penalty is applied directly to the dice roll that determines the base amount of damage that the attacking army inflicts. Note that terrain effects are at best zero and cannot be positive, and that the defender can never suffer terrain penalties. Normally the defender is the army that arrived the territory first, but this is inverted if the army that is already in the territory is currently besieging an enemy fort - in this case, the army that is arriving in the territory is considered the defender, and the army that is currently undertaking the siege will take any attacker penalties. This, for instance, makes besieging mountain forts dangerous as an enemy army can sweep in at any time to attack the besieging army and force them to engage in combat with a significant penalty.
Certain terrain types always have combat penalties for the attacker:
The following penalties stack on top of any terrain effect:
Thus, the maximum possible penalty is -4 (e.g. a naval landing into mountains).
Discipline[edit | edit source]
A cohort's discipline represents how well organized its soldiers are and how well it can hold its formation against enemy attack. Discipline increases the overall damage a cohort does against enemy soldiers, and so cohorts with higher discipline are more effective in battle. Along with morale, discipline is one of the most important modifiers that determines the quality of a cohort and army. Note that while discipline increases the damage done by a cohort against other cohorts, it does not decrease the damage that the cohort takes from the enemy army.
A general country-level discipline modifiers apply to all of a country's cohorts, and these come primarily from inventions, deity modifiers, and omens, as well as various more specific script modifiers. Certain countrywide discipline modifiers, particularly those from military traditions and trade goods, are applied only to a specific unit type. Finally, there are army-specific modifiers from commander traits, distinctions, and army modifiers more generally that may modify the discipline of all the cohorts in the army or only those of a certain unit type. All discipline modifiers that are currently applied country-wide can be viewed in the Cohorts tab of the ledger, and the total discipline modifier of any individual cohort can be viewed by hovering over its name in the unit view.
Discipline has a base value of 100%, which is adjusted by the sum of all discipline modifiers that apply to that cohort before being applied to the damage calculation - for instance, a cohort with a +20% discipline will have an overall discipline of 120%, and the amount of damage that it inflicts in battle will be multiplied by 120% (i.e. multiplied by 1.20). Most sources of discipline stack additively - for instance, two sources of +10% discipline will give a final modifier of +20% discipline. The exception to this rule is the +10% modifier from cohort loyalty, which is applied multiplicatively to the entire discipline value (i.e. the discipline value is multiplied by 1.10) after all the other modifiers have been applied. For instance, a cohort that is loyal to a character and has a +20% discipline modifier from other sources will have a total discipline of 120% x 1.10 = 132%, not 130% as might otherwise be expected.
Combat bonus[edit | edit source]
Certain military traditions, distinctions, and a few other modifiers give a combat bonus for a certain terrain type, which can be either a country or commander/army modifier and apply to either all cohorts or only cohorts of a specific unit type. A combat bonus acts as a multiplier on the damage done by cohorts against enemy cohorts when engaged in battle in a territory that has that terrain type - for instance, a +15% combat bonus on hills terrain will multiply the damage done by the cohort by 1.15 whenever fighting in a battle on a hills terrain territory. Note that, like , a combat bonus does not decrease the amount of damage a cohort takes on that terrain type.
Unit type damage[edit | edit source]
- Main article: Land units#Unit type combat effectiveness
Many unit types are stronger or weaker against certain other unit types, which is represented by a multiplier to damage inflicted by all cohorts of that unit type to all cohorts of the other unit type (represented ingame by the Vs [unit type] modifier); for instance, all heavy infantry cohorts get a +20% modifier to damage against all cohorts regardless of circumstance. Unlike most other cohort damage modifiers, the modifier to the damage a unit type inflicts or takes against other unit types is fixed and cannot be changed by any country or army modifiers.
Combat tactics[edit | edit source]
- "Combat tactics" redirects here. For naval combat tactics, see Naval warfare § Combat tactics.
Every army can be assigned a particular combat tactic that they will attempt to use in battle against other armies. The available combat tactics add a rock-paper-scissors-Spock-lizard-mechanic to battles - each tactic is strong against two other tactics, and poor against two others. Combat tactics have the following properties:
- The modifier applies to the damage done.
- The positive modifier applies only to certain unit types, and can be different for each type. The displayed "total effectiveness" of a tactic is the average of the tactic's effectiveness over each of the army's cohorts.
- The negative modifier applies fully regardless of army's composition.
- The casualties modifier affects the strength damage done in the battle applies to both armies.
- Every army always has a combat tactic chosen from the available list, with the default being Shock Action.
- The combat tactic can be changed at any time prior to a battle at no cost or cooldown.
- An army's combat tactic cannot be changed once a battle has been started, but can be overridden if a larger allied army subsequently joins the battle.
The effect of any specific tactic is not overwhelmingly powerful. See Tips: Largest impact above to compare the magnitude of other combat modifiers.
General tactics[edit | edit source]
These five tactics are available to all countries at all times.
|Tactic||Unit effectiveness||Against other tactics||Casualties||Description|
|Bottleneck||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||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||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||+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||−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 | edit source]
These other tactics are only unlocked by adopting specific military traditions.
|Tactic||Unit effectiveness||Against other tactics||Casualties||Description|
|Cavalry Skirmish||−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.
|Hit-and-Run||−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 the Barbarian military tradition "Ambush".
|Padma Vyuha||−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 the Indian military tradition "Padma Vyuha".
|Phalanx||−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.
|Triplex Acies||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 the Italic military tradition "Triplex Acies".
Offense and defense[edit | edit source]
Offense modifies the overall damage inflicted by a cohort in battle (similar to discipline), while defense modifies the overall damage that a cohort takes in battle (similar to experience). Both offense and defense modifiers are always specific to a certain unit type, and like most damage modifiers are typically given by inventions, military traditions, distinctions. Note that the total offense of the attacking cohort combines additively, not multiplicatively, to the total defense of the defending cohort. For instance, if a cohort with +20% offense is attacking a cohort with +10% defense, the overall modifier on damage will be 20% - 10% = 10% (not (120% x 90%) - 100% = 8% if they combined multiplicatively).
Experience[edit | edit source]
- "Experience" redirects here. For the related nationwide value used to purchase military traditions, see Military experience.
Every cohort has an experience value out of 100% that represents how well trained the cohort is. Every point of experience gives -0.3% damage reduction, for a maximum of -30% damage taken in combat at 100% experience. 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.
The Cohort Starting Experience and Starting Experience modifiers increase the experience that newly raised levies and newly recruited legion cohorts start with (with the starting experience modifier also increasing the experience of newly built ships), and when focused on can add up to a substantial amount of experience.
After a cohort is raised, one of the main way it accumulates experience is through fighting battles. After each battle, every cohort involved will gain experience based on the number of casualties their side took, giving the following formula:
Cohorts can also passively gain experience through the Monthly Experience Gain modifier, which gives a flat modifier to the change in experience per month. The most common way to increase cohort experience this way is to use the Drill Army action for legions, which gives a +2.50% monthly experience gain bonus (at the cost of increased army maintenance and cohort loyalty gain chance).
Every month, cohort experience also decays according to the cohort's total Experience Decay modifier, with a base of +4.50% experience decay per month. This decay can be reduced by various ideas, deities, inventions, and military traditions, but is capped at 0% (it is not possible for cohorts to gain experience through negative decay). Note that unlike the monthly experience gain modifier, which is a flat increase or decrease in experience points per month, experience decay reduces cohort experience by a certain percentage of its current experience per month. For instance, a cohort with 30% experience will have a base experience decay of 4.50% × 30 = 1.35, and assuming no other changes will have its experience reduced to 28.65% at the beginning of the next month. This means that generally, cohort experience will decay much faster at higher values than lower values. There is no extra experience decay when cohorts are reinforcing.
Cohort experience is converted into military experience in two different ways. The average cohort experience across all armies increases the country's passive monthly military experience gain by +0.006 per point (up to a maximum of +0.60 military experience if all cohorts have 100% experience), which is mostly relevant for legions (especially during peacetime). As well, levies that have been raised for at least 8 months will grant 0.015 military experience per point of cohort experience for each disbanded cohort.
Strength and morale damage[edit | edit source]
While most of the other modifiers described here apply equally to both morale and strength damage, certain unit types have modifiers that affect the amount of damage they take that apply to only one or the other, through the Morale Damage Taken and Strength Damage Taken modifiers respectively. For instance, war elephants have a -50% Strength Damage Taken modifier and a +20% Morale Damage Taken modifier, which means that they lose less strength in battle than other unit types but lose morale more quickly. Similarly, the Morale Damage Done and Strength Damage Done modifiers affect the amount of morale and strength damage a cohort inflicts, respectively.
Post-battle effects[edit | edit source]
Besides the damage inflicted on each army, battles also have direct political and personal consequences for army's commanders and the war as a whole.
Retreat[edit | edit source]
When an army is defeated in battle or is ordered to abandon the battlefield, it will attempt to retreat to a nearby friendly territory. When retreating, an army will not respond to any commands and cannot be diverted from moving to its target retreat destination, but will not engage any enemy armies (even if it passes through the same territory as one). As well, an army will recover morale while retreating, but will not reinforce any lost strength. A retreat ends once the retreating army has reached its chosen destination - note that if there is an enemy army at that destination, it will immediately engage the army.
A retreating army will usually choose to retreat at least 7-8 territories away, but is still subject to movement rules. This means that it is possible for an army to be trapped on small islands or behind forts and be unable to retreat more than a short distance, which leaves them vulnerable to being hunted down by nearby armies and destroyed right after their retreat ends, as they will be weakened from the battle and not have enough time to regain much strength or morale.
Warscore[edit | edit source]
- Main article: Warscore
The side that wins the battle - either by forcing the other side to retreat first, or completely destroying all the enemy armies involved in the battle - gains warscore depending on how many casualties each side took in the battle as a proportion of the number of soldiers involved. The exact formula can be calculated as:
Counterintuitively, this formula means that the winning side gets more warscore if they take more casualties (as well as from inflicting more casualties on the enemy side). In particular, it means that a stackwipe with zero losses on one side will give that side +3 warscore, while a battle where both sides are nearly wiped out will give up to +6 warscore.
The maximum possible warscore from all battles (including both land and naval battles) is 25. Superiority wargoals will also give additional ticking warscore to the side that has a net total of at least +10 warscore from battles.
War exhaustion[edit | edit source]
- Main article: War exhaustion
Once a battle concludes, each side takes war exhaustion based on their number of casualties as a proportion of their total maximum army strength. The total maximum army strength is calculated as how large the country's army would be (not including mercenaries or other special armies) if all of its legions and levies were at full strength, which is equivalent to the following formula:
Note that the total levy strength is equal to how many levy cohorts the country would have if they were all raised at that moment. This is not necessarily the same as the number of levy cohorts that the country actually has currently raised, since population growth or decline in the region means that the strength of the levy may have changed since the levy was raised. Overall, this means that less populous countries and those with a smaller total army strength take more war exhaustion from the same amount of casualties than more populous country would.
Commander popularity[edit | edit source]
- Main article: Popularity
An army's commander is considered personally responsible for the outcome of any battles, and will gain or lose popularity depending on the outcome of battles they are involved in. After any battle ends, the commander of the winning side will gain popularity and the commander of the losing side will lose popularity based on the casualties that they have inflicted on the other side, according to the following formula:
Note that for the losing side, the result of the formula is multiplied by -1 (i.e. made negative) in order to get the amount of popularity that the losing commander loses. As well, note that while the winning side gains popularity depending on how many casualties they inflicted on the losing side, the losing commander loses popularity depending on how many casualties the winning side (not the losing side) took. As with warscore, this somewhat counterintuitively means that a defeated commander will lose more popularity if their side inflicts more casualties, as long as they still end up losing the battle in the end.