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This guide describes the game mechanics of the combat system. For strategy advice, visit the land combat strategy guide.
Organization & Strength
Every individual brigade has two values describing its current state: organization and strength. Both of these values influence how much damage a unit can do in combat.
- Organization: Represents how orderly the formation is. Organization is regained through morale (influenced by inventions in the military tactics chain and certain leaders) and supply. Different units have different "base organisation" levels: guards have the highest, irregulars the lowest. When a regiment runs out of organization, it can no longer engage in combat. Organization damage is influenced by the discipline value of a unit: as a unit's discipline increases, it takes less organization damage. A unit with 1% discipline would take 100 times the organization damage as a unit with 100% discipline.
- Morale (Organization Regain): increases a unit's organization by 0.01 * discipline for each % of morale.
- Strength: Represents how many soldiers are in the unit. The reinforcement rate is increased largely by culture technology, available supplies, and available soldier pops. Be aware that not every soldier who gets "killed" actually dies. How many of the casualties are removed from their respective soldier pops depends on the "war hospitals" modifier, which is commonly boosted by inventions in the "Chemistry" line of the industry tech school. Since this also boosts supply limits, it is a highly important tech line. Each level of attack/defence adds ten percent of the base damage to the total strength damage. A value of 10 attack means a unit would inflict twice as much damage on attack as a unit with 0 attack.
- Attack & Defense: Base values that are used for combat die rolls.
- Recon: Improves the speed of an occupation. Recon is also used by an attacker to reduce the dig in value of that defending army, which is DIVIDED by the recon of the unit with the highest recon in the attacking army. After the first round, every time the attacker rolls higher than the defender, the remaining dig-in value is reduced by one. So, for example, if an army that has just one unit with a recon of 2 attacks a defending army that has a dig-in value of 6, when the battle begins the penalty for the attackers' roll will be 3. After the first round, the attackers need to have a higher roll than the defenders for three rounds to completely remove the dig-in penalty.
- Width: This determines how much space a brigade occupies in combat. This is important because frontage is always limited: only so many units can participate in a battle at a time. Combat width can be negatively modified by terrain. Finally, width is reduced over the course of the game as technology is researched. Frontage in the early game is massive, while by the end of the game frontage will be limited to only 10 units in the front line.
- Maneuver: Flanking ability. A unit with 1 maneuver value can target the unit directly in front of it; if there's no such unit it can target units diagonal to it. Higher values increases maximum targeting distance by one for each point. Practically, this means that a cavalry unit with x maneuver value could engage any enemy within 2x+1 positions on the front (only one at a time).
- Support: Support is a percentage value and represents the percentage of damage a unit in the second row can do to enemy units. This means that units such as artillery can do more damage in support than they can on the front line. 3 support means that a unit would do 3 times the damage in the second row than they would if they were on the front-line.
- Terrain: Terrain gives a negative dice modifier to an attacker's dice roll. Effectively it reduces the amount of damage an attacker can do. The modifier is dependent on the type of terrain.
- Forts: Forts add a 10% military tactics and discipline bonus to a defending unit per level of fort. In other words, forts reduce the casualties taken by the defender.
- Military tactics: Reduces strength damage taken.
- Discipline: Reduces organization damage taken and regained.
Each round of combat lasts for five days:
- Units identify their target: for infantry this will be the unit directly in front of them. If no one is in front, they are allowed to target diagonally. Cavalry can always target diagonally.
- A random die (0 - 9) is rolled for both the attacker and the defender
- Modifiers are applied: entrenchments (dig-in), leaders, terrain bonuses, and potential gas attacks
- The net difference between the attacking and defending roll determines damage inflicted.
- Modifiers are applied: military tactics reduce the damage taken, while organization and strength also modify damage
- Damage impacts both strength and organization, and damage occurs simultaneously for both attacker and defender
- Organization damage inflicted = Base Damage From Roll * (1 + attack / 10) * (100 / Discipline of Enemy Unit)
- Strength damage inflicted = Base Kills From Roll * (1 + attack / 10) / (1 + Enemy's Tactics / 100)
- Damage is inflicted to soldier POPs, after being reduced by the country's Military Hospitals modifier.
Typically, organization will run out before strength. When this happens, the unit will attempt to retreat. Retreat is only possible into provinces with no enemy presence. This therefore excludes provinces with fights going on! If no avenues of retreat are possible, the unit surrenders and is lost.
A positive war score is achieved through two primary avenues: winning battles and occupying provinces. The maximum war score that can be achieved through winning battles is 50% in Heart of Darkness and 25% in earlier versions, thus for wars with ambitious war goals such as state acquisition it is necessary to be offensive and occupy territories.