本页面描述了陆军单位作战的游戏机制。有关战略建议，请访问陆战策略。
组织度与兵力
每个旅都有两个描述其当前状态的值：组织度和兵力。这两个值都会影响一个单位在战斗中所能造成的伤害。
- 组织度：表示这个旅组织有序的程度。组织度可以通过士气（受军事战术链中的发明和某些将领的影响）和补给来恢复。不同类型的单位有不同的“基础组织度”等级：民兵和骑兵最低，坦克最高。当一个旅的组织度归零，它就不能再参与战斗了。组织度损伤受单位纪律的影响：单位纪律越强，所受组织度损伤越小。1%纪律的单位和100%纪律的单位相比，前者受到的组织度损伤是后者的100倍。
- 士气（组织度恢复）：每增加1%士气，单位组织度就增加0.01×纪律的数值。
- 兵力：代表这个单位包含多少士兵。增援效率主要通过文化科技、可用的补给和可用的士兵人群来增加。要知道，不是每一个“被杀”的士兵都会死。有多少伤亡者从对应士兵人群中移除取决于“战地医院”修正，这项修正通常由工业科技中的“化学与电学”子类的发明所推动。由于这个子类的科技也会提高补给上限，因此对减少兵力损失来说它至关重要。每一级的攻击/防御增加10%的基础兵力伤害。攻击为10的单位和攻击为0的单位相比，前者所造成的伤害是后者的两倍。
战斗指标
- 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.
战斗
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.
Retreat
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.
War Score
A positive war score is achieved through four primary ways: winning battles, completing war goals from casus belli, blockades 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. The maximum war score that can be achieved from blockades are 25%. Blockades also affects war exhaustion.