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# Land warfare

This page deals with combat mechanics. For information on the recruitment and maintenance of armies see army. For the individual unit types see land units.

Land warfare is the deployment and maneuvering of military assets against an enemy in most cases resulting in combat between opposing armies. In EUIV most combat is land-based and, while the naval aspect of war holds importance, losing the land war is usually tantamount to defeat in general. The art of land warfare is therefore of significant importance, and its complexities are discussed here as fully as possible.

## Combat interface

The conclusion to a normal land battle.

Combat is not determined by mere numbers such as modifiers and dice-rolls, but through a complex simulation in which units deployed into two rows of positions for each side, allowing units to fight the enemy units in front of them, the enemies at their flanks if possible, and move between different positions if needed. All the while, the system retreats destroyed or low-morale units and deploys reinforcements and reserves as well.

The combat system, while not being entirely obvious or intuitive, can be seen through the combat interface which allows the player to see which regiment is fighting which, and who is moving where.

## Terrain

Terrain map. Border pixels belong to the province to their southeast.

Terrain used to be randomly selected, but is now static to each province. Entering a battle in rough terrain will incur a negative modifier to the attacking army, with different terrains having different modifiers. Terrain for each province is shown in both the terrain and simple terrain mapmodes. Terrain shows a natural-looking map, while simple terrain color-codes each province by its terrain type; both have tooltips showing terrain type, fort level, and the current winter if any.

Terrain
Supply limit

Local defensiveness

Movement cost

Combat width

Attacker penalty
Glacial +4 −1
Farmlands +10 +10%
Forest +3 +25% −20% −1
Hills +5 +10% +40% −25% −1
Woods +6 +10% −20% −1
Mountain +4 +25% +50% −50% −2
Grasslands +8
Jungle +5 +50% −25% −1
Marsh +5 +30% −25% −1
Desert +4 +5%
Coastal Desert +4
Coastline +6
Drylands +7
Highlands +6 +10% +40% −25% −1
Savannah +6
Steppe +6

### Crossing penalties

A crossing penalty that reduces all dice rolls is applied to attackers under the following circumstances:

• Crossing a river: -1 to all rolls.
The presence of rivers between a province and its neighbors is indicated in the province window by a small river icon. The tooltip over this icon will show which neighboring provinces require a river to be crossed in order for an army to reach the province.
• Crossing a strait: -2 to all rolls. See straits for a list.
• Amphibious landing: -2 to all rolls.
Includes attacks from sea or landing directly with ships at port.

For attackers that originate from multiple provinces, they will all receive the crossing penalty if any one of them would normally receive it alone. All crossing penalties are removed if the attacking leader has a higher maneuver rating than the defending leader. The check on leader maneuver rating is performed daily, so a high maneuver leader can still swing the tide of battle even if he joins an engagement late.

## Deployment

### Army composition

Main article: Army#Composition

To maximize the effectiveness of an army, a proper mixture of troops is important.

### Combat width

Combat width determines how many units can actively participate in a battle at one time. For every 1 combat width, 1 additional regiment can be placed in the front or back row if sufficient troops are available. The base combat width is 15.[1] As military technology advances, a country's combat width increases, allowing them to use more soldiers effectively at once. (All countries other than Native Americans start with tech level 2 or 3, so their starting combat width will actually be 20.)

 Military technology level Combat width 0 2 5 6 8 11 14 16 18 20 22 24 26 15 20 22 24 25 27 29 30 32 34 36 38 40

The terrain of the province also has a strong effect on combat width, particularly since percentage modifiers are used. This can allow a small army to last longer or even fight evenly against a large one if fighting on favourable terrain, such as the mountains. The final combat width is rounded down to the nearest integer.

Note: The combat width used in a battle will be that of the highest value among the participants.

### Unit deployment

The game uses an undocumented algorithm to automatically deploy land units on the battlefield for each side of the battle. Through observation and controlled experiments, the community has suggested a theory that the game seems to follow, dependent on the rough size and composition of each army.

NB: The player plays no part in unit deployment.

#### For the smaller army

• If there is not enough infantry to fill the entire first row:
1. Deploy all infantry in first row.
2. Deploy as much cavalry at the sides of the first row.
3. Deploy all artillery in the second row. If there are more units in the second row than the first, then redeploy artillery to the first row until both rows are even.
4. If there is still space remaining in the second row, deploy all remaining cavalry onto the second row, beginning from the edge of the first row then inwards.
• If there is enough infantry to fill the entire first row:
1. Deploy all infantry in first row, except for X[Unknown value] positions to each side.
2. Deploy X units of cavalry to each side in the first row.
3. Deploy all artillery in the second row.
4. If space left in the second row, deploy all remaining infantry in the second row beside the artillery, except for Y[Unknown value] positions to each side.
5. Deploy all remaining cavalry in the second row, beginning from the edge and going inwards.

#### For the bigger army

1. Deploy all infantry in the first row that can be positioned to attack enemy units in the first row, except for X[Unknown value] positions to each side.
2. Deploy all cavalry in the first row that can be positioned to attack the enemy units in the first row.
3. Deploy all artillery in the second row.
4. If space left in the second row, deploy as much infantry in the second row besides the artillery as there are positions available behind the infantry in the first row.
5. If space left in the second row, deploy as much cavalry in the second row besides the infantry as there are positions available behind the cavalry in the first row.

## Combat sequence

When two warring armies meet in a province a battle will commence. A battle will last until one side is routed or annihilated.

### Phases

Combat is divided into a series of 3-day phases. Phases alternate between Fire and Shock, with the Fire phase happening first.

### Target selection

Units in the front row can attack any enemy unit within their horizontal flanking range. Normally they will only engage enemies that are directly ahead of themselves, but they can sometimes execute flanking attack regardless if it will be more effective at reducing the enemy's combat ability. This typically occurs if the unit is facing an enemy artillery regiment or a particularly outdated unit; in this case the unit may choose to attack the flanks of a stronger enemy unit nearby. Artillery are the only units that can attack from the back row, but they will only deal 50% damage from that position.

### Die roll

At the beginning of each phase, each side rolls a die. The result is used to determine the morale damage and casualties inflicted by that side during each of the three days of that phase.

The result is computed as following:

${\displaystyle D_{result}=D_{roll}+Ls_{Atk}+Up_{Atk}-Ls_{Def}-Up_{Def}-T_{mod}}$
• Die roll (${\displaystyle D_{roll}}$): A random number between 0-9, rolled for each entire side at the beginning of each phase (not each day).
• Leader skill (${\displaystyle Ls}$): The leader skill for that phase (Fire or Shock).
• Attacking unit attack pips (${\displaystyle Up}$): The attack pips for the attacking unit for the current phase, or Morale pips if computing morale damage. Note all units attack during every phase---here "attack" does not refer to which army is attacking.
• Defending unit defense pips: The corresponding defense pips for the defending unit.
• Terrain modifiers (${\displaystyle T_{mod}}$): Harsh terrain may give a penalty to the attacks of the attacking army.

### Casualties

Casualties caused by each unit during each day are computed as follows:

${\displaystyle C=C_{base}\cdot Us_{Atk}\cdot Um_{Atk}\cdot (1+CA_{Atk})\cdot {\frac {Ud_{Atk}}{Ut_{Def}}}}$
• Base casualties (${\displaystyle C_{base}}$): Base casualties is determined by the die result according to the following formula:
${\displaystyle C_{base}=15+5\cdot D_{result}}$
• Attacking unit strength (${\displaystyle Us_{Atk}}$): If the attacking unit has below its maximum of 1000 men, damage will be reduced proportionally.
• Attacking unit modifier (${\displaystyle Um_{Atk}}$): The attack modifier from the attacking unit's technology, e.g. "Infantry Fire".
• Attacking unit Combat Ability (${\displaystyle CA_{Atk}}$): Any Combat Ability bonuses the attacking unit has.
• Attacking unit Discipline (${\displaystyle Ud_{Atk}}$): The Discipline of the attacking unit. Note that Discipline does also increase Military Tactics, so it increases defense indirectly.
• Defending unit Tactics (${\displaystyle Ut_{Def}}$): The Tactics of the defending unit.

### Morale damage

${\displaystyle M_{dam}={\frac {C_{base}}{600}}\cdot Us_{Atk}\cdot Um_{Atk}\cdot UM_{Atk}^{max}\cdot (1+CA_{Atk})\cdot {\frac {Ud_{Atk}}{Ut_{Def}}}}$
• 6 base casualties translates to dealing 1% of the attacking unit's maximum morale as morale damage. Note that the modifiers may be different. Units also use their morale pips, but the pips added by the general still use shock and fire pips during the shock and fire phases respectively.
• Attacking unit maximum morale (${\displaystyle UM_{Atk}^{max}}$): Note that this is the maximum morale of the attacking unit, not the current morale.
• After recent observations and a combat tooltip[2], it appears that the tech level multiplier to shock and fire damage affects morale damage as well.
• There is an additional contribution that also affects units that are deployed, but not actively participating in combat

## Combat statistics

### Military tactics

Military tactics reduces the amount of damage your troops take in combat. Military tactics is increased by military technology. It is also multiplied by discipline.

Military technology level 0 4 6 7 9 12 15 19 21 23 24 30 32
Military tactics 0.5 0.75 1.0 1.25 1.5 1.75 2.0 2.25 2.5 2.75 3.0 3.25 3.5

### Pips

Each military unit has offensive and defensive stats in three categories: fire, shock, and morale. Offensive stats are represented by yellow pips, and defensive stats by green pips. During each combat phase, each unit will use its offensive pips to increase damage dealt, and its defensive pips to mitigate damage received.[3]

This implies that offensive pips are preferable when you field a larger army than your opponent, and vice-versa for green pips. Understand that a larger army with longer combat width will have a larger surface area of attack. Assume the enemy has an army with 10 infantry and 10 artillery, and you have just 10 infantry. You will suffer significantly fewer casualties with defensive fire pips, because it will reduce damage from both the infantry and artillery fire. Conversely, if you have the larger army, you want higher fire pips on your infantry and artillery because you have 2 attacking regiments per defending enemy regiments.

The strongest statistical pre-artillery composition with no regard to cost, consists of high proportions of cavalry and a high shock pip Leader. Understand that tier 1 cavalry has 1 shock and 0 fire modifier, and tier 1 infantry has 0.35 fire and 0.5 shock modifier. Combined with a shock Leader, you will inflict significantly more damage during the shock phase. This also means that defensive shock pips are preferable early game to defend your army from the strength of shock damage.

Post level 7 military tech, the combined fire pips of tier 2 infantry and tier 1 artillery balances fire and shock pips, and therefore Nomadic and Civilized nations. If you plan to recruit artillery units commensurate with the length of your combat width, a fire pip Leader is now preferable.

### Flanking range

Flanking range determines the horizontal range in which a unit may make a flanking attack. The base flanking range is 1 for infantry, and 2 for cavalry and artillery. There are military technologies which increase the flanking range of units as the game progresses.

Military technology level 0 10 18 23 28 30
Improved flanking range 0 +25% +50% +100% +125% +150%
Flanking range for infantry 1 1 1 2 2 2
Flanking range for cavalry 2 2 3 4 4 5
Flanking range for artillery 2 2 3 4 4 5

A unit that has 75% or more of its troop strength will fight at 100% flanking range. If between 50 and 75% strength, they will fight at 75% flanking range. When between 25 and 50% strength they will fight at 50% of their flanking range.

 Unit strength Flanking range 1000−750 749−500 499−250 249-0 100% −25% −50% -75%

The final range is always rounded down to the nearest integer.

### Morale

Morale is an important factor in fighting battles. Each day of combat a unit will take a Morale hit of 0.01 or 0.02 regardless of taking damage from an enemy regiment. If taking casualties from an enemy, additional morale damage will be inflicted. Once an army's overall Morale value has been reduced to zero the army will attempt to retreat. Retreat cannot happen until both a fire and a shock phase have completed, so an army that has its morale reduced to 0 before that point will be destroyed. This destruction is known as a stackwipe.

A unit that has its morale drop below 0.50 is flagged as disorganized, which is indicated by a small flame next to its morale bar on the map and interface. A disorganized army is unable to start moving until its morale has recovered above 0.50. Newly trained regiments at low land unit maintenance will often fall below this threshold.

If an army loses a battle while having low enough morale to be disorganized, they will be forced to retreat to a controlled province (owned, allied in war, or occupied by player or allies). This province can be very far away from where the battle took place. They will usually retreat to one with high development, a fort, and no adjacent enemies. While retreating, it cannot be engaged in combat or be controlled until it reaches the safer province (or in extreme circumstances if it recovers to 100% morale before reaching the destination). The army also moves slightly faster, and will recover morale at a normal rate during the retreat. If there are no available controlled provinces to retreat to within a large range, the army will shattered retreat to one province away. The army can then be immediately re-engaged, often with 0.00 morale (assuming a monthly tick has not yet completed). This can be devastating as an offensive tactic, but can also affect a player as well.

A controlled retreat is manually ordering an army to retreat from battle after the initial fire and shock phases, and while still having greater than 0.50 average morale for the army. This allows the player to control the destination of the shattered retreat. If the morale of an army is less than 0.50 you cannot control the destination. If multiple armies have converged into a battle, it is possible that some armies will have enough morale for a controlled shatter, while others may not (often the initial stack in the battle).

Winning a battle gives the winning armies 50% of their maximum morale as of patch 1.15. Retreating from a battle will reduce the other allied armies' morale relative to the portion of troops leaving the engagement as of patch 1.15.

After every battle is fought an army must spend some time not fighting for its morale to recover. The normal morale recovery on the 1st of every month cannot occur while in combat.

• A shattered army will get an extra morale bonus as it stops retreating.
• Morale is not gained while forced marching

#### Modifiers

The following contributes to the maximum morale of a nation's army.

• Army Maintenance: Ranging from 0.51 at minimum maintenance to 100% at maximum maintenance.
• Ideas and policies:
+20%
• French idea 2: Elan!
• Prussian idea 3: Army Professionalism
+15%
• Defensive idea 2: Military Drill
• Air idea 2: Cross of Agades
• Native idea 1: Counting Coups
• Polish idea 7: Focus on Field Defenses
+10%
• Plutocratic idea 2: Abolished Serfdom
• American idea 4: Lessons of Valley Forge
• Aragonese idea 7: Protect the Little Folk
• Aymaran idea 5: The Tinku Rites
• Aztec idea 4: Eagles and Jaguars
• Bulgarian idea 6: Military Flexibility
• Carib idea 3: Resistance towards the Pailanti'po
• Catalan idea 6: 'Lliures o Morts'
• Chachapoyan idea 1: Warriors of the Clouds
• Charruan idea 6: Garra Charrua
• Cherokee idea 5: Ghigau
• Creek idea 7: Red Sticks
• Daimyo idea 4: The Five Rings
• Desmondian idea 3: Gaelic Bastion
• Finnish idea 7: The Anjala Conspiracy
• French ducal idea 7: La Petite Nation
• Fulani Jihad idea 4: Imans and Emirs
• Galician idea 5: Santiago y Cierra!
• Imerina idea 2: The Twelve Sampys of Imerina
• Ionian idea 1: Frankokratia
• Kangra idea 3: Martial Heritage
• Khmer idea 1: Preah Ko Preah Keo
• K'iche idea 6: K'iq'ab's Vengeance
• Krakowian idea 1: Legendary Legacy
• Luban idea 4: Encourage the Kasala Tradition
• Manipur idea 2: Martial Traditions
• Mayan idea 7: Caste War
• Medri Bahri idea 5: Independent Traditions
• Mexican idea 7: Grito de Delores
• Miao idea 3: Unity of the Tribes
• Nepali idea 5: The Royal Kumari
• Nivernais idea 4: True Frenchmen
• Sadiyan idea 1: Land of Glory
• Semien idea 1: Legacy of Queen Judith
• Serbian idea 7: Balkan Hajduks
• Slovak idea 7: Slovak National Awakening
• Songhai idea 3: Jihad Against the Pagans
• Taungu idea 5: Chakravartin
• Trebizondian idea 5: The Lessons of the Fourth Crusade
• Yarkandi idea 5: Holy Warriors
• Yi idea 7: Children of the Black Tiger
• Ajuuraan ambitions
• Athenian ambitions
• Circassian ambitions
• Colonial ambitions
• Dai Viet ambitions
• Kievan ambitions
• Punjabi ambitions
• Ryazan ambitions
• Religious-Quantity: Field priests and Soldier's prayer books
+5%
• Quality-Religious: The Military Zeal Act
• Researching military technology:
• Military technology (0): +2.0
• Military technology (3): +0.5 (cumulative +2.5)
• Military technology (4): +0.5 (cumulative +3.0)
• Military technology (15): +1.0 (cumulative +4.0)
• Military technology (26): +1.0 (cumulative +5.0)
• Military technology (30): +1.0 (cumulative +6.0)

Various National bonuses:

• Prestige: +10% at 100 Prestige, -10% at -100 Prestige
• Power Projection: +10% at 100
• Being the Defender of the Faith: +5%
• Piety (Muslim only): +10% (at 100% Piety)

Religions:

• Shia: +5%
• Protestant Church aspect Saints accept Prayers: +5%
• Reformed War focus (requires Wealth of Nations DLC) +10%
• Vajrayana: +5%
• Shinto: +10%
• Sikh: +10%
• Inti with Expanded Mitma Policy: +10%
• Nahuatl: +10%
• Tengri with either Shia, Nahuatl or Sikh as syncretic faiths: +5%

Government:

• Noble: +10%
• Revolutionary Empire: +10%
• Daimyo: +10%
• Merchant Republic with Aristocrats: +5%
• Republican Dictatiorship: +10%
• Revolutionary Republic: +10%
• Ambrosian Republic: +5%

#### Morale recovery

Every month, a regiment recovers a 15% of its maximum morale. The following contributes to a nation's morale recovery speed.

• Regiment is in home territory: +5%
• Various events, decisions, and modifiers
• Certain ideas and policies as follows
+10.0%
+5.0%
• Pskovian idea 2: Legacy of Daumantas
• Fully Offensive
• Persian ambitions
• Expansion-Defensive: Local Army Organization
• Humanist-Defensive: The Preparation Act
• Religious-Quantity: Field priests and Soldier's prayer books

### Insufficient support

The old combined arms bonus that used to give +25% bonus damage in EU3 has been removed. It has been replaced with a penalty called insufficient support that is applied to armies with too much cavalry, and reduces military tactics by -25%. Each technology group has a limit to how much cavalry an army may contain before the penalty is applied. This threshold is checked daily even during battles, and is based on the actual headcount of individual soldiers instead of regiments.

 Icon Technology group Western Eastern Anatolian Muslim Indian Chinese Nomad Sub-Saharan New World Max cavalry 50% 60% 50% 80% 50% 50% 100% 50% 50%

## Forts

Forts are used to protect a nation from invading armies.

### Fort level and garrison

The following affect fort level:

• Capital province: +1 fort level for every capital province
• Fort buildings: +2 fort level per building level.

Each fort level increases the garrison of the province by 1000. Maximum garrison size is also influenced by following ideas and policies:

+25%
• Quantity idea 6: Conscripted Garrisons
• Ming idea 1: Nine Garrisons of The Great Wall
+20%
• Betsimisaraka idea 1: People of the Coast
+10%
• Divine idea 5: Onward Christian Soldiers
• Italian idea 4: Trace Italienne
• Kangra idea 4: Control of the Hill Forts
• Slovak idea 4: Land of Castles
• Innovative-Quantity: The Garrison System

Garrison recovers monthly at base rate of 5% plus 1% per base manpower of the province. The rate is also increased by the following ideas and policies:

+25%
+15%
• Austrian idea 2: Military Frontier
+10%
• Divine idea 5: Onward Christian Soldiers
• Influence-Quantity: Guerilla Warfare

### Fort maintenance

Each building level of fort cost 1 per month. Forts can be mothballed by the nation that controls them. Mothballing will reduce the fort maintenance by a half but remove fort level and current garrison from the city. Capital cities without fort buildings cannot be mothballed, and they will always keep a minimum fort level of 1 and garrison of 1000 even if mothballing is available and toggled on. Garrison will recover at normal rate after mothballing is cancelled.

Mothballing or not, fort maintenance can be reduced by following modifiers:

−20%
• French idea 5: Vauban Fortifications
• Ladakh idea 2: Fortified Mountain Cities
• Swiss idea 3: Alpine Defensiveness
• Sligonian ambitions
• Innovative-Quantity: The Garrison System
−15%
• Andhra idea 4: Great Forts of the East
• Northumbrian idea 4: A Land of Castles
• Luxembourg idea 4: The Fortress of Luxembourg
• Orleanaise idea 1: Sieges of Orleans
−10%
• Defensive idea 5: Defensive Mentality
• Austrian idea 2: Military Frontier
• Catalan idea 4: Fortifying Catalonia
• Kangra idea 4: Control of the Hill Forts
• Laotian idea 7: Laotian Hill Warfare
• Mutapan idea 3: Mutapa Architecture
• Nubian idea 7: Fortified Strongholds
• Semien idea 2: Mountain Kingdom
• Slovak idea 4: Land of Castles
• Tarascan idea 5: Fortified Frontier
• Innovative-Defensive: Superior Fortifications

The Monastic Order government also gives -20% Fort Maintenance.

### Zone of control

Unmothballed fort buildings (not counting the free fort level in the capital) provide a zone of control.

A zone of control restricts the movement of enemy armies through the province with the fort, and provinces immediately adjacent to it. After an enemy army enters a province within the zone of control, they can only move from there to two other provinces: the province containing the fort, and the province they came from. This means that forts form a barrier against enemy armies; if placed so that there's no way around the fort(s) the enemy is forced to siege one or more forts in order to get at the rest of one's country. This can provide time to muster up one's forces, or simply time for the enemy to get hurt by attrition while sieging. The Zone of control also applies for occupied forts. An army who belongs/allied to the province owner can not pass as long as the fort is not liberated.

Unfortified provinces within the zone of control will also automatically be recaptured if the fort isn't under siege and the province is vacated for one month.

AI ZoC: If the AI can enter a province legit in any way it will always use the shortest way ignoring the ZoC.

### Sieges

When hostile troops enter a province and stop moving, a siege/occupation will begin. To progress, the assailant requires a minimum of 3000 men per 1000 garrison. If the province has no fort, 1000 men is enough and occupation is guaranteed within a month. Any unit types can be used for sieging, but for sieging a fortified province, only infantry will be used in an assault, and artillery speeds the siege up (see below). Progress in a siege will never decrease as long as attackers are continuously present; however, if all attackers leave the province, it will be instantly reset.

Besieging armies will always take at least 1% base attrition, even if the province is unfortified.

A besieging army always count as attacker and will receive the province penalty and, depending on the way they entered the province, an additional crossing penalty when a battle takes place.

The Garrison can be ordered to leave the Fort and fight the hostile army. If the Garrison loses the fight the province and Fort will become occupied. Keep in mind that the AI will never send the garrison to fight the hostile army even when the garrison have superior numbers.

#### Phases

A siege progresses in phases. Each phase has a base length of 30 days and modified by

• Fort defense: +1% per defender's 1% fort defense and province defensiveness
• Siege ability: -1% per attacker's 1% Siege Ability
• Tactics difference: 6.25% per 0.25 military tactics difference to both sides. E.G. If the player's tactics is 0.5 higher than the enemy, the player's siege will be 12.5% faster and the enemy's siege will be 12.5% slower. Only the base tactics value counts, bonus from discipline have no effect on phase time.

Siege ability is influenced by the following ideas and policies:

+20%
• Offensive idea 5: Engineer Corps
+10%
• Beninese idea 2: Isiatua
• Dutch idea 6: Army Sappers
• Smolenskian idea 7: Tsar Mortars
• Luxembourg ambitions
• Innovative-Offensive: Modern Siege Weapons
• Quality-Religious: The Military Zeal Act

Various Modifiers:

• War exhaustion: -1% per point
• Army Tradition: +5% at 100
• Spy network: +20% at 100
• Tengri with Coptic syncretic faith: +10%
• Hindu with Shakti as divinity: +5%

Fort defense is influenced by the following ideas and policies:

+25%
• Afghan idea 2: Shadows of the Hindu Kush
• Bremish idea 6: Bremish Walls
• Cypriot idea 5: Cypriot Fortifications
• Divine idea 3: True Defender of the Faith
• Hamburger idea 3: Walls of Hamburg
• Jerusalem idea 6: Crusader Castles
• Knights Hospitaller idea 1: Defense of the Faith
• Theodorian idea 5: Mangup and Kalamita Forts
+20%
• Defensive idea 5: Defensive Mentality
• Breton idea 3: Breton March
• Chickasaw idea 6: Lessons of Ackia
• Couronian idea 1: Legacy of Sword Brethren
• Dai Viet idea 3: Autonomous Villages
• Ethiopian idea 3: Hostile Borders
• Galician idea 2: Galicia la Bella
• Hormuz idea 2: Protecting the Islands
• Ionian idea 2: Castles of the Angels
• Krakowian idea 4: Casimirian Fortifications
• Lorraine idea 1: The Vosges
• Luxembourg idea 2: The Ardennes
• Malvi idea 4: Fortified Strongholds
• Maratha idea 2: Forts of Maharashtra
• Mazovian idea 2: Mazovian Frontier
• Nivernais idea 5: Bridges of the Loire
• Savoyard idea 1: Repel the French
• Thüringian idea 2: Fortifications of Erfurt
• Trebizondian idea 2: Pontic Mountains
• Tverian idea 2: Defend Against Muscovy
• Italian (cU) ambitions
• Mesoamerican ambitions
• Novgorodian ambitions
• Permian ambitions
• Sumatran ambitions
+15%
• Bosnian idea 7: Over the Hills and Through the Woods
• Central Indian idea 1: Securing Our Defenses
• Client State idea 3: Fortified Border
• Danziger idea 6: Continued Independence
• Finnish idea 1: Expand Viborg
• Fulani Jihad idea 2: Unrighteous Kings
• Guarani idea 6: Repel the Bandeirantes!
• Imerina idea 4: Fortify the Highlands
• Japanese idea 5: Sakoku
• Kazani idea 6: Settle Down
• Khivan idea 6: Ichan Qal'a
• Kievan idea 3: Fending Off The Invaders
• Kutai idea 4: Anti-Piracy Measures
• Malagasy idea 1: Fortify the Coastline
• Mapuche idea 1: Mapuche Pucaras
• Mossi idea 5: Land of the Ancestors
• Nepali idea 2: Land of Peaks
• Provençal idea 4: Tarascon Castle
• Pueblo idea 3: Mesa Settlements
• Québécois idea 4: Fortifications of Quebec
• Rajput idea 2: Fortifying Rajputana
• Sadiyan idea 3: Hills and Jungles
• Siberian idea 4: Siberian Backwoods
• Siddi idea 3: Impregnable Island Fortress
• Shan idea 1: Fortified Cities
• Songhai idea 2: Independence from Mali
• Teutonic idea 5: Expand the Marches
• Vindhyan idea 2: Forts of the Vindhyas
• Yaroslavlyian idea 6: The Two Towers
• Desmondian ambitions
• Manipur ambitions
+10%
• Andean idea 6: Hidden Cities
• Beninese idea 4: The Walls of Benin
• Chachapoyan idea 3: Summit Fortresses
• Cham idea 7: Resisting Foreign Rule
• Cherokee idea 6: Mountainous Isolation
• Holstein idea 1: Limes Saxoniae
• Kongolese idea 1: The Kongo River Basin
• Lan Xang idea 6: Merchants of Vientiane
• Navarran idea 1: Dorretxeak
• Nizhny Novgorod idea 4: Citadel Of Russia
• Polotskian idea 4: Land of Strongholds
• Tarascan idea 5: Fortified Frontier
• Tupi idea 7: Wall Builders
• Moldavian ambitions
• Espionage-Defensive: The Privy Council Establishment Act
• Influence-Defensive: Local Militias
• Innovative-Defensive: Superior Fortifications
+5%
• Croatian idea 4: Antemurale Christianitatis
• Italian idea 4: Trace Italienne
• Ming idea 1: Nine Garrisons of The Great Wall

Various Modifiers:

• Hindu with Vishnu as divinity: +20%
• Norse with Tor as divinity: +10%
• Being pious as a Muslim: up to +20%
• Coptic: +10%
• Lucky nation: +10%
• Certain events can temporarily increase siege ability or fort defense.

The mean number of phases to finish a siege for a particular starting bonus is as follows:

 Starting bonus Starting success % Mean phases Sieges per year -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 No fort -100.00% -92.86% -85.71% -78.57% -71.43% -64.29% -57.14% -50.00% -42.86% -35.71% -28.57% -21.43% -14.29% -7.14% 0.00% 7.14% 14.29% 21.43% 28.57% 35.71% 100% 43.18 30.51 25.24 21.44 17.42 14.75 12.65 10.87 9.41 8.20 7.24 6.48 5.78 5.13 4.52 3.86 3.27 2.82 2.46 2.17 1 0.28 0.40 0.48 0.57 0.70 0.82 0.96 1.12 1.29 1.48 1.68 1.88 2.10 2.37 2.69 3.15 3.72 4.32 4.95 5.60 12

"Sieges per year" is computed at the default phase length of 30 days.

#### Die roll

At the end of each siege phase, a die (1 to 14) is rolled. The following modifiers are then applied:

• Siege status. The most important modifier. As the siege goes on, this bonus will increase from its starting value of 0 to a maximum of 12 depending on previous die rolls.
• Leaders siege skills caps at 6.
• Artillery. Adding artillery to a siege will add a 1 to 5 bonus.
• Required number of artillery for this modifier = [modifier] * [Fort]
• [Fort] = 2 for a Castle, 4 for a Bastion, 6 for a Star Fort, 8 for a Fortress. The Capital receives an additional point even for a province without a Fort.
• [modifier] = desired modifier (1 to 5).
• 1 besieging artillery always provides a modifier of 1.
• Each 1000 artillery soldiers count as 1 artillery. e. g. having 10 regiments with 100 artillery each is the same as 1 regiment with 1000.
• Blockade. If the province is coastal and not completely blockaded, a -1 penalty is applied, with an additional -1 if the defender owns the province. Partial blockades (anything less than 100% for the province in question) have no effect on sieges. Note that the blockading fleet doesn't have to be owned by the same nation as the sieging army, or even a part of the same war to help in a siege.
• Fort Level. The defender's Fort Level is applied as a penalty.
• Obsolete Fort If the attacker's tech allows to build advanced forts, they gain bonus to siege old forts. e. g. If attacker can build level 3 fort and sieging level 1 fort, gains +2 bonus to die rolls.
• Having less than half of the maximum garrison +1.
• Walls Breached. If the sum of die roll, Artillery bonus and Obsolete Fort bonus is 14 or greater, breach occurs. Breaching the walls gives attacker +1 siege bonus. Recurring breaches will increase the bonus by 1, up to +3.

The highest possible starting bonus is thus +6 for the leader, +5 for artillery, -2 for Fort level 1, +3 for obsolete fort bonus for a total of +11.

#### Effects

The die roll may result in an increase of the siege status, which improves the results of future siege stages. Maximum siege status values goes up with fort building level. (12/13/14/15 for fort building level 1/2/3/4)

Roll Result Effect Garrison losses Attacker Loses
1 Disease Outbreak Status Quo 0 -5% attackers
5 - 11 Supplies Shortage +1 siege status -1% garrison 0
12 - 13 Food Shortage +2 siege status -3% garrison 0
14 - 15 Water Shortage +3 siege status -5% garrison 0
16 - 19 Defenders Desert +1 siege status -10% garrison 0
20 or more Surrender Siege successful - -

Therefore, the attacker needs at least a net +6 bonus to have a chance of ending the siege.

#### Assault

The attacker may choose to assault the garrison with their infantry if the walls have been breached at least once. This can result in a speedy conclusion of the siege at the cost of 5 Military power, and usually lots of lives. The attacker loses roughly 1.5 times as many troops as defender do. Only infantry can assault. If all infantry units of the attacker are killed before the defenders are defeated, the remaining cavalry and artillery will continue the siege normally. Only breaches*5000 men can be part of an assault per day.

## Mechanics of an army

Main article: Army

### Exile

An exiled army can be identified by a black flag attached to its unit icon. It can't fight, siege provinces or explore, and it won't lift fog of war even in the province it's in. However, it can traverse any territory (other than wasteland) without needing military access. It still suffers attrition, and you can move its regiments between armies, though you can't mix its regiments into a non-exiled army or vice versa.

An army will become exiled under the following circumstances:

• When a war ends, any army still in territory it doesn't have peacetime access to is exiled. This prevents it from being permanently stuck in a place it can't get out of, as well as preventing several exploits.
• When a war begins, any army in a neutral or hostile province that it only had access to through a military access agreement is exiled. This prevents you from placing troops outside your territory in preparation for war. An army in uncolonized land or the territory of a subject or ally (that is, someone you have an alliance with) won't be exiled, even if the ally isn't called into the war.

It will stop being exiled when

• it enters a province that you or a subject control or own, or
• it boards a transport ship that moves into a sea zone or is currently in one.

### Looting

Every province has a loot bar. This is the amount of gold available in the province and is determined by its development level: a province will gain 1 gold for every increase of 1 development level. You can loot provinces you occupy or those you're sieging, but troops must be present to do so. The amount of loot taken depends on the number and type of troops in the province. A full strength infantry/cavalry/artillery regiment loots 0.1/0.3/0.05 ducats per months.[4] When a province's loot bar is empty no more loot can be taken from that province. Only at six months after the last successful looting will a province start to recover, at a rate of 10% each month.

The modifiers of a fully looted province are:[5]

 −25% Local goods produced modifier −25% Local tax modifier +30% Local recruitment time +30% Local shipbuilding time −10% Supply limit modifier −50% Local sailors modifier −33% Institution spread

Looting greatly reduces the owner's tax income and unit construction speed. Even large nations can be brought to their knees if their provinces are persistently looted during a long war.

### Attach to army

This action attaches your army to a friendly army, causing your army to travel and fight alongside the friendly unit without further input from the player. The army can be detached at any time except in battle. An attached army cannot board transports. Attaching units to an AI army will change its behavior, making it bolder and more willing to actively engage enemies.

### Attack natives

The native population of a colony or uncolonized province can be eliminated using the attack natives military action. A native army equal in size to the local native population (rounded to the nearest thousand) will spawn immediately and must be defeated in battle to clear out the native population. This action costs military power proportional to the native population, aggressiveness, and ferocity, and will permanently reduce the potential value of the province from the native assimilation bonus. The elimination of all natives in a province will prevent any future raids on the local colony or any passing armies.

### Scorched earth

An army in an owned and controlled province may scorch the earth for 5 military power. The scorched earth province modifier will last for 60 months and has the following effects:[6]

 −33% Local goods produced modifier −50% Local tax modifier +25% Local defensiveness −50% Supply limit modifier +0.01 Monthly autonomy change −50% Institution spread

Scorching the earth is useful when you're too weak military to fend off attackers and your provinces are likely to be occupied. It causes sieges to take longer, increases attrition (both together hurting the enemy's manpower), and makes the provinces less valuable to the attacker while they're occupying them. You lose income in the meantime, but if you were going to lose control of them anyway it's good to make them less valuable for the enemy.

### Hunt rebels

Clicking the hunt rebels icon in a selected army panel will set the army to automatically travel to and fight rebel armies that appear in its surroundings. The army will return to its previous position after the rebels are dispatched. Armies that are ordered to move will stop hunting rebels. An army will not hunt rebel armies that are larger than it is.

### Forced march

Forced march makes an army move 50% faster, but costs 2 military power for each province the army marches through. Forced march is available at administrative technology 15. Armies that are forced marching do not recover morale.

## Strategies and tactics

### Defensive wars

• Defending territory is easier than conquering it, and the bigger the battlefield the easier it gets.
• Your enemies want to besiege and conquer your provinces sometimes to the point where their armies become separated and easily dispatched.
• The more the border is fortified, the better. Higher level forts means more time to take them down, more men needed to assault/siege and more attrition.
• Sometimes they will also use hunter-killer armies to destroy your armies and protect their sieges.
• Disturbing the enemy's siege will reset the siege timer. Even though siege progress and garrison casualties will stay if the sieging army wins the battle, the siege timer is the main factor in winning a siege.
• If your main army is bigger than the enemy's hunter army, destroy it and then hunt the siege armies. Most of them will flee, but you can often catch them by first engaging with a smaller/faster stack, then bringing in reinforcements.
• If your forces are inferior to your enemy's hunter army, evade it and focus on killing siege armies. This will force the enemy to split up his forces to replace the siege army.
• If the enemy is concentrating his forces in one province or in a few neighbouring ones, attacking him can be dangerous.
• But that means his armies can not move.
• Besiege his land instead, while spreading out your forces. You should be able to besiege more provinces than him.
• If he sends troops while continuing his siege, destroy this army rather than continuing your siege.
• If the forces he sends are too big to be destroyed, evade them and attack the siege armies instead.
• Use scorched earth on your territories.
• This will cost you a lot of tax income.
• 10% attrition makes even standing in this province a deadly undertaking and will burn your enemy's manpower very fast.
• Besieging such a province is practically impossible.
• Try to control your enemy's movement and lure him into these provinces.
• A common tactic when trying to lure the enemy into unfavorable terrain (useful when you have an inferior or smaller army) is to leave an army that is no more than 70% of their strength in said province. The AI will attack the bait army, and once they are halfway there, cannot cancel their action. Additional reinforcements after the fact will most often lead to victory due to the massive penalties incurred in mountainous or hilly terrain.

### Standing or Situational Army

• A standing army contains a number of troops with this number only changing slightly, usually being near the force limit.
• A standing army has the advantage of a military deterrence. Nations which can field less troops than this army will be much less likely to attack.
• Even though the number of troops is not the only point of accessible reference for warfare capabilities, it's the most obvious.
• Even when kept at low maintenance, a standing army will be battle ready much faster than troops which have to be recruited first.
• If unrest is high and rebels are spawning continuously, a standing army will most likely be cheaper than recruiting and disbanding troops repeatedly.
• Recruiting regular troops costs manpower. After the standing army is created, these reserves can refill.
• A situational army contains only small numbers of troops, and will recruit additional regiments when needed.
• Upkeep cost for nonexistent regiments is even lower than for regiments with the maintenance slider at minimum.
• Hostile nations will possibly misjudge the military capabilities, thus could be baited into a war they cannot win.
• If recruiting regular troops for the war, you will use up a chunk of manpower just to get up to forcelimit. On the other hand, with Administrative ideas and Innovative ideas, cost and availability of mercenaries is competitive with regular troops, with recruiting time extremely short and no consumption of manpower. This makes them ideal troops for this strategy.

### Assessing the Enemy's Strength

Correctly assessing the enemy's capability for warfare is essential for good preparation and thus decisions, and there are multiple indicators which allow deducing it:

• Number of troops. This most direct indicator tells the minimum strength of a nation. Only very rarely will a nation use all available resources to conduct a total war, but the possibility still exists.
• Available manpower. If they can't replace their losses but you can, a bloody battle can be a win for you in the long term even if you technically lose it - relentlessly attacking with replenishing troops, you will eventually outnumber them.
• War exhaustion. Along with low manpower, this not only makes their armies fight worse and siege slower, it decreases war enthusiasm, making them more ready to accept peace. This keeps the war short and reduces losses for you.
• Military technology. More troops does not necessarily mean victory. How advanced these troops are matters too. Though bear in mind that not every level gives an advantage on the battlefield.
• Tech group. When having the same level of military technology, Anatolian/Nomadic groups are stronger than Western/Eastern groups in early game.
• Idea groups. The opponent's ideas, if focused towards the Army and/or Navy, can be decisive. Also, many nations have ideas boosting their troops (France, Turkey and so on).

### Sieging

For fastest sieging:

• Bring lots of artillery if finances permit.
• Siege as many provinces as is safe to do so ("carpet sieging").
• Distribute one artillery to each fort being sieged---one artillery will give a +1 bonus regardless of Fort Level.
• Look out so that your occupations wouldn't get recaptured by hostile forts nearby.
• Only march out from the fortless province within other fort zone of control, if that fort is under siege(besieged forts don't recapture provinces)
• If any artillery is left over, concentrate it with the best siege leader---in terms of successful sieges per length of time, each point of bonus is worth more than the last.
• A conquered/liberated fort will start with a garrison of 100. Each month it will receive reinforcements. The best tactic is to start a new siege directly after the enemy army has left the province. To stop the reinforcement for the fort at only 1 men is required. An assault against a garrison of 300 is won within 5 days.

### Others

• Use a small portion of your army to lure the enemy into attacking it, then come in with your main army and crush the enemy.
• Pay attention to the terrain. While river crossings are often only a minor inconvenience (and have no effect if your leaders have superior maneuver scores), a much lower combat width due to mountains or forests can hugely shift the outcome of a battle.
• As long as you are in allied territory, you can instantaneously move your leader from army to army. This way you use one good leader to virtually fight all battles, saving you military monarch points. You can also remove a leader from an army in hostile territory (in order to appoint him elsewhere) by reorganizing all its regiments into a new army
• Armies of relatively the same size will often retreat with no or very low morale. Often chasing them down and annihilating them is possible and should be done. Be careful however when chasing a retreating army too far - this can get you into an unfavourable strategic position.
• Attrition is deadly - your manpower is your most limited resource (unless you're Russia or a fast expanding Ottomans). Avoid it as much as possible. A 10,000 men army with 5% attrition will burn 500 men each month from your manpower pool.

## References

1. See in /Europa Universalis IV/common/defines.lua: BASE_COMBAT_WIDTH = 15.0
2. "During the Shock phase and after the dice roll and other modifiers have been added together, the unit makes an attack on an enemy unit. The Shock Modifier directly affects damage dealt to morale and number of casualties inflicted." "During the Fire phase and after the dice roll and other modifiers have been added together, the unit makes an attack on an enemy unit. The Fire Modifier directly affects damage dealt to morale and number of casualties inflicted."
3. http://steamcommunity.com/app/236850/discussions/0/864976115458051703/
4. See in /Europa Universalis IV/common/defines.lua under INF_LOOT, CAV_LOOT and ART_LOOT.
5. See in /Europa Universalis IV/common/static_modifiers/00_static_modifiers.txt (Static modifiers#Looted).
6. See in /Europa Universalis IV/common/static_modifiers/00_static_modifiers.txt (Static modifiers#Scorched Earth).
Warfare
 Land warfare Army • Land units • Discipline • Manpower
 Naval warfare Navy • Naval units • Sailors
 Other concepts Casus belli • War exhaustion • Military tradition • Leaders • Alliance