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This article is accurate for the latest versions of EU3, Napoleon’s Ambition, In Nomine, Heir to the Throne and Divine Wind.

The Military is the basis for warfare within EU3 and is controlled from the Domestic Military interface. From here the numner of regiments and ships can be found in addition to the relevant force limts.

Preferred units

The military system is based on a model of "preferred units" for land units. Core provinces will produce preferred units. Owned provinces that other countries have cores own may recruit the preferred units of that country (even if from a different technology group). All the units already built will be automatically changed to the new preferred one, except for mercenary units. When the preferred unit type is changed, all units of that type have their morale set to zero. Technology determines what units are available to choose from. Units of similar technology levels have different strengths and weaknesses: some favor offensive or defensive, others favor shock or fire damage. The game has three basic unit types:


The regiment is the basic land military unit that consists of 1,000 soldiers. Each regiment is classified as either infantry, cavalry or artillery. There are two classifications of regiments which can be recruited through the course of the game, mercenaries and levies.


Several modifiers change the cost of units, but the base costs, set in defines.txt, are 9Ducats.png for infantry, 21Ducats.png for cavalry, and 30Ducats.png for artillery. Mercenary costs are detailed below.


Levies are troops who are recruited and then join your armed forces. Infantry tend to take half as long to recruit as cavalry or and a third of the time for artillery. Each regiment recruited depletes the manpower pool by 1000. The price depends on inflation, slider choices, and several other factors. Recruitment time is significantly increased by war exhaustion, and reduced by military province buildings and the Recruitment Act.


Mercenaries may be bought from the recruit management interface. If mercenaries are available they will be displayed at the bottom portion of the window. Mercenary availability will differ with each geographic area and each area has a pool of available mercenaries that may be purchased by any country. They may only be recruited on one's home continent. If no mercenaries are available in the province selected, other nations have bought the mercenaries available from that pool and the player will need to wait for it to slowly replenish before they can purchase any. Mercenaries take much less time to recruit than regular troops and do not deplete manpower; this makes them useful when troops are needed very quickly (e.g. to defend a vulnerable colony or when there is an unexpected opportunity to attack), when the manpower pool is depleted, or when heavy casualties are expected.

Mercenary units have some distinct disadvantages in comparison to regularly trained units. Mercenaries will contribute only 1/3 of the amount of military tradition that a regular unit would after a battle, will not upgrade when you change your preferred unit type, cost twice as much to maintain, and will immediately disband if you go bankrupt. Mercenaries' maximum morale does not include any modifiers other than those from maintenance and technology, which means they will usually have lower morale than regular troops. Mercenaries are distinguished from regular troops by their naming scheme. Levies are named after the nation's provinces (Picardie's 1st, Cadiz's 3rd) while mercenaries are named after their captain. When an army is selected, mercenaries are displayed in light blue and regular troops in dark blue.


Any nation with a standing army or navy will pay maintenance upkeep, a cost deducted monthly from annual income. Maintenance can be set anywhere from 100% down to 50%. If maintenance is set to 50%, no reinforcements will be sent. Maintenance set at 100% provides a +2.00 morale boost, while 50% provides no boost. Any nation that exceeds its force limit is penalized with a higher maintenance cost. The penalty is proportional to the ratio over force limit. For example, maintenance of a 10-regiment army in a country with a force limit of 5 will cost twice as much as maintenance of a 10-regiment army in a country with a force limit of 10 or greater.


When regiments suffer casualties and their number falls below 1000, they will have to be reinforced. This is done automatically by draining men from the national manpower pool. Troops can reinforce anywhere but do so much more quickly in home territory. The Quantity slider and the Quartermaster adviser increase the rate of reinforcement.

Maintenance Costs

The maintenance cost of a unit is linked to its recruitment cost (2.5%). Regiments built in provinces with military province improvements that reduce recruitment cost (Such as an armory) will cost less to maintain than those built in provinces without. Cost reductions are applied retroactively, meaning that a regiment recruited from a specific province before any improvements were built will still get a reduction in its maintenance cost if recruitment cost-reducing improvements are built there after it has been recruited. This also applies to ships, which means that keeping prizes taken in naval combat can inflate your naval maintenance needlessly. Therefore, it is recommended to designate specific provinces as 'recruitment provinces' early on in the game and recruit solely from these provinces in order to get the most benefit from your military buildings.

National Ideas and Sliders can also affect the maintenance costs of a regiment. Aristocracy reduces the cost and upkeep of cavalry while Plutocracy increases it, Serfdom reduces the cost and upkeep of infantry while Free Subjects increases it, Defensive reduces the cost of artillery while Offensive, and Land reduces the cost of all land troops while increasing the cost of ships. Finally, Quantity reduces the cost of infantry while Quality increases it. As for ideas, Press Gangs reduce ship costs and upkeep by 50%, while Regimental System reduces land upkeep by 20%.

Force Limit

The force limit of a country reflects how many regiments they can field without a penalty of increased maintenance. This might also be referred to as the national support limit. The grand navy and grand army national ideas, Feudal Monarchy, Tribal Federation and Steppe Nomad governments, and the land/naval policy slider all increase limits, as do the Naval and Army Organizer advisors. Naval buildings increase naval force limit, while the highest level Army building dramatically boosts land forcelimit. The Holy Roman Emperor gets an additional bonus of 2x(number of countries in the HRE). Note that %modifiers to tax do not affect force limits and even base tax of colonies is included. Starting in Divine Wind an overlord gets half of his vassals' land forcelimits.

forcelimit = 0.25 * [ (sum of base_tax + tax_income) + fixed forcelimit modifiers ] * %modifiers + (HRE bonus) + (vassal bonus)

In the In Nomine expansion the naval forcelimit calculation has changed significantly:

naval forcelimit = 0.5 * [ (sum of base_tax + tax_income) + fixed forcelimit modifiers ] * %modifiers

Some tax_income modifiers:

Some fixed forcelimit modifiers:

Other factors affecting the naval forcelimit:

  • Only non-colony (pop 1000+) coastal provinces are counted.
  • Contribution of provinces of a different culture group (even if accepted) or non-state religion is halved.
  • Contribution of provinces with no land connection to the capital (even on the same continent) is quartered.
  • Contribution of provinces on a different continent from the capital with a land connection is divided by 20.

Supply Limit

The supply limit of a province determines how many men can be supported without suffering from Attrition. The minimum supply limit in the game is 1.

Supply Base Formula

Supply Base = 1 + (0.2 * Base Tax) + Land Fort Bonus

Land Fort bonuses:

  • Fort 1: 0.5
  • Fort 2: 1.0
  • Fort 3: 1.5
  • Fort 4: 2.0
  • Fort 5: 3.0
  • Fort 6: 4.0

In Heir to the Throne there is an additional +1 for coastal provinces.

Supply Limit Formula

Supply Limit = (Supply Base x Province Status x Tech Level Modifier)
Province StatusBase Multiplier
Allied or MA4
Enemy / Unowned1

Weather Modifiers: Weather modifiers are not included in the Supply Limit displayed for a province. Instead, they are indicated by the Max Attrition being greater than 5 (except for maneuver), in which case you can hover the cursor over Max Attrition to see what additional modifiers apply. For practical purposes, these modifiers should be subtracted from the Supply Limit to see the "true" limit. Note that weather changes immediately before monthly attrition is applied and therefore you may not be able to tell in advance what weather penalties will apply in a province.

  • -2 for mild winter, -5 for normal winter, -10 for severe winter
  • -5 for tropical
  • -5 for desert summer


Attrition occurs when the number of troops in a province is too large for the current Supply limit.

If attrition is applied it is calculated on the basis of the number of troops in a province, not the number of regiments. Every 1000 troops require 1 supply limit. So 1 regiment of 250 and 1 regiment of 750 require only 1 supply limit. In tropical provinces 5 is added to the required supply. For example: 1000 troops in a tropical province would require a supply limit of 6 to avoid attrition. The tropical penalty is not applied if your country's capital is in a tropical province. The level of attrition applied is a percentage value applied to the whole force calculated as 1% per 1,000 men over the support limit. Fractions of 1,000 men create attrition of a fraction of 1%. The attrition rate is capped by the maximum attrition rate in the province.

Attrition is evaluated whenever a force arrives in a province and on the 1st of each month. Arrival attrition does not occur for troops that arrived by naval movemennt in a port (but can occur for troops boarding ships). Attrition does not occur for troops that are in combat including troops arriving in a province and immediately entering battle. Note that battles with natives also have this effect so fighting natives can be used to avoid attrition. Attrition occurs prior to receiving reinforcements and therefore if your reinforcement rate is adequate your regiments will remain at full strength.

Attrition in "In Nomine"

Attrition and blockades each add to War exhaustion. Fleets of pirates running blockades on a colony/province will also cause quite high attrition. In one game, seven blockaded ports resulted in an Attrition rating under War Exhaustion of +11,4. In comparison, the bonuses for peace(-0,08) and defender of the faith(-0,02) are insignificant. This can break an empire through increased revolt risk. In the example game, they were present in Acapulco Bay while the player controlled Apolco/Mayan/Aztec territory but did not have an explored sea route to the west coast of North America.

Scorched Earth

From In Nomine manual: This is a new ability that your troops can use on provinces you own. If you do this, it will seriously damage the economy of the province, leading it to produce little or no tax, but it will also reduce the number of troops that can be supported by the province and the attrition rate you get from having too many troops in a province. If you retreat in the face of a superior enemy, this can be a powerful weapon.

Naval Transport

Naval transport has slightly different rules to other supply limits. A transport fleet has a support capacity of 6,000 men and no other modifiers except leader manoeuvre rating have any effect. Attrition is based upon the total land forces present in transports in a sea province.


Combat consists of a series of combat resolutions. A single combat resolution lasts for a 3-day period, beginning with a 3-day Fire combat resolution, followed by a 3-day Shock combat resolution. This alternating process completes until one army runs out of morale. This system means that fire combat resolutions are slightly more common, and that combat against defeated or retreating forces will be resolved entirely in the fire combat resolution.

Actual combat is resolved using the following formula. The process is the same for shock combat resolutions as it is for fire, simply using fire attack/defense rating instead of shock attack/defense ratings. On each day of combat the game evaluates how many casualties each side inflicts on the other by the following formula:


Modified roll = (Attack + Dice) - (Defense + Terrain) + (Leader Differential)

Final Casualties: Base Roll * Tech Level Modifier * Discipline * 6

  • If the Modified roll is 13 or greater, then use 12 as the modified roll.
  • If the Modified roll is less than 13 but greater than 1, then subtract 1 from the modified roll.
  • If the Modified roll is 1, then use the modified roll.
  • If the Modified roll is less than 1, then the use 2^(modified roll).


  • Attack: the attack rating (shock or fire rating depending on the combat resolution).
  • Dice: A random number (in the range 0-9) representing luck for the combat resolution
  • Terrain: Terrain modifiers are applied to both the attacker and defender's offensive roll - it subtracts from the attacker and adds to the defender. Cavalry takes double penalties (but does not get double benefit on defense).
    • Forest/Marsh/Hills: -1 for the attacker, +1 for the defender
    • Mountains: -2 for the attacker, +2 for the defender
    • River Crossing: -1 for the attacker, +1 for the defender
  • Defense: the defense rating (shock or fire rating depending on the combat resolution).
    • In IN, if there an artillery unit in the back row, it gives half its defense rating to the infantry unit in front of it as a bonus.
  • Leader Differential: The difference in capability between the opposing leaders.
  • Tech Level Modifier: The Shock or Fire multiplier based on the tech level of the army's nation.
  • Discipline: A damage modifier. So discipline of 125% increases the damage done by the unit by 25%, discipline 90% reduces the damage done by 10%. The national idea Esprit de corps increases discipline by 25%, but requires a Land Tech level of ≥53.
  • In IN, if an artillery unit is in the back row, its damage is halved.

Military tactics is a concept introduced in Heir to the Throne. It is a value that increases with some Land Tech levels and it makes a big difference in combat. As the value of Military tactics increases the amount of damage taken decreases. The amount of damage done is modified by the military tactics value by the following formula: Damage = Base damage / (1 + Military Tactics)


Modified roll = Dice + Offensive Morale Attack Modifier - Defensive Morale Defense Modifier

Final Morale Damage = Modified roll * Tech Level Modifier * 0.08

  • If the Modified roll is 13 or greater, then use 12 as the modified roll.
  • If the Modified roll is less than 13 but greater than 2, then subtract 1 from the modified roll.
  • If the Modified roll is less than 2, then use 1 for the modified roll.

Note that general and terrain modifiers do not apply to Morale.


In a naval combat, both sides have a positioning value, determining what percent of their firepower is effective at any given time. This serves the purpose of limiting the effectiveness of additional ships, much the same way that combat width limits the effectiveness of reinforcement in land battles. The maximum positioning value is equal to 100% - (number of cannons in fleet / 100), meaning the optimum number of cannons to have in a fleet is 5000. The actual positioning value during a combat is determined by the average speed of the fleet and the maneuver value of the admiral.


Leaders  • Maintenance  • Morale  • Manpower  • Ship types (Big ship  • Light ship  • Galley  • Transport)  • Land unit types (Infantry  • Cavalry  • Artillery)  


Assault  • Basic Warfare  • Casus Belli  • Combat • Making peace • Siege • Supply & attrition • War Capacity  • War Exhaustion