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# 陆战

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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 this results 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 the main cause of defeat. The art of land warfare is therefore of significant importance, and its complexities are discussed here as fully as possible.

## 战斗界面

The conclusion to a normal land battle.

Combat is not only 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 (with high enough flanking range), 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 which is moving where.

## 地形

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

Terrain used to be randomly selected (when?), but is now static for each province. Entering a battle in rough terrain will incur a negative modifier to the attacking army, with different types of terrain 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. Here is a list of the types of terrain and the modifiers which they grant.

### 穿越惩罚

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

• Crossing a river: -1 to all rolls.
The presence of a river in between a province and its neighbors is indicated in the province window, through a small river icon. Mousing 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.
This includes an attack from sea or a 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.

### 围城期间爆发的战斗

Normally, the "attacker" is defined as whichever side moves into a given province last, while the "defender" is whichever one was already occupying the area. However, if a given army is besieging a province that contains a fort and is attacked by troops owned by, or allied with, whoever currently controls the fort, the roles are switched: the siege army is treated as the "attackers," and those attempting to break the siege are the "defenders." Attacker penalties from terrain are applied to the siege army, while attacker penalties from river/strait crossings are nullified regardless of any leaders' Maneuver pips.

The player can take this into account when building forts, as well as when choosing which provinces to siege and which besieged provinces to prioritize sending their troops to. Also note that this only applies to provinces with forts.

## 战斗部署

### 战斗宽度

 军事科技等级 战斗宽度 0级 2级 5级 6级 8级 11级 14级 16级 18级 20级 22级 24级 26级 15 20 22 24 25 27 29 30 32 34 36 38 40

### 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, the game will prioritize to:
1. Deploy all infantry in the first row.
2. Deploy as much cavalry as possible to 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 it will 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, the game will prioritize to:
1. Deploy all infantry in first row, except for X[Unknown value] positions to each side.
2. Deploy X units of cavalry on each side of the first row.
3. Deploy all artillery on the second row.
4. If space is left on the second row, deploy all remaining infantry in the second row next to 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

For an army bigger than the combat width, the game will prioritize to:

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 is 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 is 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 hostile 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 to the opponents each day in the three-day-phase.

The result is computed as following:

${\displaystyle D_{result}=D_{roll}+Ls_{Atk}+Up_{Atk}-(enemy)Ls_{Def}-Up_{Def}-T_{mod}}$
• Die roll (${\displaystyle D_{roll}}$): Is 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 Pips).
• 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 (in this case "attack" refers to the attacking side).

### 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 are 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 less than its maximum of 1000 men, damage will be reduced proportionally.
• Attacking unit modifier (${\displaystyle Um_{Atk}}$): Determined by unit type and military technology level and. See template:Cumulative_mil_tech
• 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.

Several ideas exist which increase the amount of damage done in the Fire phase and decrease the amount of damage received in the Shock phase, respectively.

Ideas that increase fire damage dealt:

+10%
• Date idea 4: Dragon Corps
• Dutch idea 7: Platoon Fire
• Jaunpuri idea 1: Purbias
• Hatakeyama idea 7: Sakai-shu
• Isshiki idea 5: Inadome Gunnery
• Münster idea 6: Bommen Berend
• Shimazu idea 5: Tanegashima
• Smolenskian idea 2: The Armories of Smolensk
• Tirhuti idea 4: Purbias
• Utsunomiya idea 2: Legacy of Nasu no Yoichi
• Beninese ambition

Ideas that reduce shock damage taken:

−15%
• Ando idea 1: March of Akita
−10%
• Assamese idea 3: River Warfare
• Baluch idea 2: Hani and Sheh Mureed
• Hausan idea 5: Sarkin Yaki
• Irish idea 1: Irish Endurance
• Kanem Bornuan idea 5: Fixed Military Camps
• Butua ambition
−5%
• Bohemian idea 3: Wagenburg

Ideas that increase shock damage dealt:

+10%
• Great Yuan idea 4: Keshik and Weijun
• Nanbu idea 6: Chosonji Temple

### Morale damage

${\displaystyle M_{dam}=Casualties\cdot Morale/600}$
• 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 (${\displaystyle Morale}$): 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 recommended if the player fields a larger army than their opponent, and vice-versa for defensive pips. This is because a larger army with higher combat width will have a larger surface area of attack. If, say, the enemy has an army with 10 infantry and 10 artillery, and the player only has 10 infantry. The player will suffer significantly fewer casualties with defensive fire pips, because it will reduce damage from both infantry and artillery fire. Conversely, if the player has a larger army, they would want higher offensive pips on their infantry and artillery because they have 2 attacking regiments for every defending enemy regiment.

The recommended pre-artillery composition with no regard to cost, consists of high proportions of cavalry and a high shock pip Leader, as 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, the player will inflict significantly more damage during the shock phase. This also means that defensive shock pips are recommended early game to defend the player's army from the enemy's shock damage.

After military technology level 7 , the combined fire pips of tier 2 infantry and tier 1 artillery balance fire and shock pips, for both Nomadic and Civilized nations. If the player plans on recruiting an amount of artillery units equal to the length of your combat width, a fire pip Leader is now recommended.

### 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. Below is a table with said military technology levels and how much they increase flanking range.

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 left will fight at 100% flanking range. If they are in between 50 and 75% of their 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.

Several ideas give increased cavalry flanking range:

+50%
• Albanian idea 4: Hit and Run
• Lan Na idea 6: Elephant Charge
• Mossi idea 2: Cavalry Raids
• Najdi idea 5: Arabian Horsemanship
• Kazani ambition
+25%
• Arabian idea 2: Arabian Horses

### 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 damage taken from an enemy regiment. If it is 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 prioritize to retreat to a province with high development, a fort, and no adjacent enemies. While retreating, it cannot be engaged in combat or 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 very low to even no morale, if a monthly tick has not yet completed. This can be devastating as an offensive tactic, but may also affect the player as well.

A controlled retreat is manually ordering an army to retreat from battle after the initial fire and shock phases, and while it still has greater than 0.50 average morale. This allows the player to control the destination of the shattered retreat. If the morale of an army is less than 0.50 the player can not control the destination. If multiple armies have converged into a battle, it is possible that some armies will have enough morale for a controlled retreat, 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 a battle is fought, an army must spend some time without fighting for its morale to recover. The normal morale recovery on the 1st of every month can not occur while in combat.

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

#### Modifiers

The following modifiers contribute to the maximum morale of a nation's army:

• Army Maintenance: Ranging from 0.51 at minimum maintenance to 100% (points in morale?) 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
• Polish idea 7: Focus on Field Defenses
+10%
• Plutocratic idea 2: Abolished Serfdom
• Amago idea 4: Ten Brave Warriors
• 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
• Chiba idea 2: Dream of Masakado
• 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!
• Garhwali idea 3: Martial Diplomacy
• Great Yuan idea 2: A Savage Kingdom Holy and Enchanted
• Imerina idea 2: The Twelve Sampys of Imerina
• Ionian idea 1: Frankokratia
• Kangra idea 3: Martial Heritage
• Khmer idea 1: Preah Ko Preah Keo
• Kikuchi idea 4: Fortify the Domain
• Krakowian idea 1: Legendary Legacy
• K'iche idea 6: K'iq'ab's Vengeance
• 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
• Nanbu idea 1: Genji in the North
• Native idea 1: Counting Coups
• Neapolitan idea 4: Crush the Power of the Barons
• 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
• Shiba idea 4: Atsuta Shrine
• Shimazu idea 1: Satsuma Hayato
• Shoni idea 2: Defender of Japan
• Slovak idea 7: Slovak National Awakening
• Songhai idea 3: Jihad Against the Pagans
• Takeda idea 1: Leader of Kai Genji
• Taungu idea 5: Chakravartin
• Trebizondian idea 5: The Lessons of the Fourth Crusade
• Uesugi idea 4: Dragon of Echigo
• Yarkandi idea 5: Holy Warriors
• Yi idea 7: Children of the Black Tiger
• Ajuuraan ambition
• Athenian ambition
• Circassian ambition
• Colonial ambition
• Dai Viet ambition
• Kievan ambition
• Punjabi ambition
• Ryazan ambition
• 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 Power Projection
• Being the Defender of the Faith: +5%
• Piety (Muslim only): +10% at 100 Piety

Religion:

• 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 (republic?): +10%
• Revolutionary Empire: +10%
• Daimyo: +10%
• Merchant Republic with "Aristocrats" Faction in power: +5%
• Republican Dictatorship: +10%
• Revolutionary Republic: +10%
• Ambrosian Republic: +5%
• Peasants Republic: +5%

#### Morale recovery

Every month, a regiment recovers 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
• Armies that win battles will gain a significant boost to morale, to prevent situations where an army is stack wiped due to winning a narrowly fought battle and then immediately being attacked. The amount of morale regained depends on the strength of the enemy army defeated relative to their own strength.
• Certain ideas and policies as follows

+10.0%
+5.0%
• Pskovian idea 2: Legacy of Daumantas
• Fully Offensive
• Persian ambition
• 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. Here is a table of how much % of an army can be cavalry without incurring this penalty for every tech group.

 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%

## 堡垒

### 堡垒等级与驻军

• 首都： 首都省份获得+1 堡垒等级。
• 要塞：每个建筑等级+2 堡垒等级。

+25%
• Quantity idea 6: Conscripted Garrisons
• Ming idea 1: Nine Garrisons of The Great Wall
• Toki idea 4: Strategic Castles
+20%
• Betsimisaraka idea 1: People of the Coast
+10%
• Divine idea 5: Onward Christian Soldiers
• Garhwali idea 2: Himalayan Kingdom
• Italian idea 4: Trace Italienne
• Kangra idea 4: Control of the Hill Forts
• Slovak idea 4: Land of Castles
• Innovative-Quantity: The Garrison System

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

### 堡垒维护

−20%
• French idea 5: Vauban Fortifications
• Ladakh idea 2: Fortified Mountain Cities
• Odoyev idea 6: Fortification Efforts
• Swiss idea 3: Alpine Defensiveness
• Sligonian ambition
• 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

### Sieges

When hostile troops enter a province and stop moving, a siege/occupation will begin. To progress, the attacker 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 instantly reset.

Besieging armies will always take at least 1% base attrition, even if the province is unfortified. This rule only applies to enemy-owned provinces, however - when besieging friendly provinces to retake them from the enemy, this rule is ignored.

A besieging army always count as the 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.

#### Sortie

The garrison can be ordered to make a sortie to fight the hostile army, at the cost of 10 military power. (The ‘Sortie from siege’ button is shown on the siege screen.) If the garrison army, which consists only of infantry, loses the fight the province and fort will become occupied. This can be used to win a battle in which both sides are evenly matched.

#### Phases

A siege progresses in phases. Each phase has a base length of 30 days and is 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, bonuses 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
• Otomo idea 7: Kunikuzushi
• Smolenskian idea 7: Tsar Mortars
• Luxembourg ambition
• 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 (only with Mare Nostrum enabled)
• Tengri with Coptic syncretic faith: +10% (only with The Cossacks enabled)
• Hindu with Shakti as divinity: +5% (only with Wealth of Nations enabled)

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
• Ito idea 5: Network of Forty-Eight Fortifications
• 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
• Ogasawara idea 1: Shinano-Shugo
• Savoyard idea 1: Repel the French
• Thüringian idea 2: Fortifications of Erfurt
• Trebizondian idea 2: Pontic Mountains
• Tverian idea 2: Defend Against Muscovy
• Yamana idea 6: Isolated Heartland
• Italian (cU) ambition
• Mesoamerican ambition
• Novgorodian ambition
• Permian ambition
• Sumatran ambition
+15%
• Amago idea 3: Fortified Strongholds
• 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
• Kazani idea 6: Settle Down
• Khivan idea 6: Ichan Qal'a
• Kievan idea 3: Fending Off The Invaders
• Kikuchi idea 7: Central Stronghold
• 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 ambition
• Manipur ambition
+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
• Garhwali idea 2: Himalayan Kingdom
• 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 ambition
• 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
• Toki idea 4: Strategic Castles

Various Modifiers:

• Hindu with Vishnu as divinity: +20% (only with Wealth of Nations enabled)
• Norse with Tor as divinity: +10% (only with El Dorado enabled or a save converted from Crusader Kings II)
• Being pious as a Muslim: +20% from 100 piety
• 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.

#### Dice 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 depending on previous dice rolls. The maximum starts at 12 for a Castle or capital fort and is increased by 1 for each building level above a Castle, up to a maximum of 15 for a Fortress.
• Artillery. Adding artillery to a siege will add a 1 to 5 bonus (with the ‘Napoleonic Warfare’ ability further +3 Artillery bonus vs fort bonus).
• The bonus is equal to the total number of artillery regiments divided by (fort building level + 1), as listed in the table below
• A single regiment of artillery will always give at least a +1 bonus, regardless of fort level.
• 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.
Fort building level Bonus +1 Bonus +2 Bonus +3 Bonus +4 Bonus +5 Bonus +6 Bonus +7 Bonus +8
Capital without fort 1 reg. 2 reg. 3 reg. 4 reg. 5 reg. 6 reg. 7 reg. 8 reg.
Castle (Fort level 2) 1 reg. 4 reg. 6 reg. 8 reg. 10 reg. 12 reg. 14 reg. 16 reg.
Bastion (Fort level 4) 1 reg. 6 reg. 9 reg. 12 reg. 15 reg. 18 reg. 21 reg. 24 reg.
Star fort (Fort level 6) 1 reg. 8 reg. 12 reg. 16 reg. 20 reg. 24 reg. 28 reg. 32 reg.
Fortress (Fort level 8) 1 reg. 10 reg. 15 reg. 20 reg. 25 reg. 30 reg. 35 reg. 40 reg.
• Blockade. If the province is coastal and not completely blockaded, a −2 penalty is applied, or −1 if the attacker is the rightful owner of 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 technology allows the building of more advanced forts, they gain bonus to siege old forts. e. g. If attacker can build Star Forts (building level 3) and is sieging a Castle (building level 1), they gain a +2 bonus to dice rolls.
• Insufficient Garrison: Having less than half of the maximum garrison gives the attacker a +1 bonus. If the fort has no garrison whatsoever (i.e., if the fort has been mothballed during this month), then the province is treated as unfortified and the siege will automatically succeed.
• Walls Breached. Each time the walls are breached, the breach status value will increase by 1, to a maximum of +3. If this value is at least +1, then the fort can also be assaulted (see below).

The highest possible starting bonus is +14: a capital fort (−1), obsolete by 3 fort levels (+3), with an insufficient garrison (+1), with a 6-siege general (+6) and at least 5 regiments of artillery (+5). The worst possible starting bonus is −11, for a level 8 fort in a capital (−9) with no blockade (−2).

#### 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 the attacker's maximum fort building level. (12/13/14/15 for fort building level 1/2/3/4). Maximum breach status is always 3.

• If the unmodified roll is 1, a Disease Outbreak happens—the attacking army loses 5% of its troops, and the siege does not progress.
• If a breach occurs, ignore all results on the table below except for "Surrender". If the fort does not surrender, add 1 to the breach status and 2 to the siege status. A breach occurs if:

${\displaystyle {\text{unmodified roll}}+{\frac {{\text{Artillery bonus}}+{\text{Obsolete Fort bonus}}}{3}}+{\frac {\text{Attacker's maximum fort building level}}{10}}\geqslant 14}$ Or the fortress is under an artillery barrage (see below)

• Then look up the modified die roll on the table below.
Roll Result Effect Garrison losses
4 or less Status Quo
5 – 11 Supplies Shortage +1 siege status −1% garrison
12 – 13 Food Shortage +2 siege status −3% garrison
14 – 15 Water Shortage +3 siege status −5% garrison
16 – 19 Defenders Desert +2 siege status −10% garrison
20 or more Surrender Siege successful

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

#### Artillery barrage

If you have at least one artillery regiment currently sieging a fort, you can create a breach in the walls by spending 50 military power (only available from 1.20 onward).

#### 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 costs 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 ${\displaystyle ({\text{breach status}}\times 5000)}$ 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 either:

• enters a province that you or a subject control or own, or
• 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 to be looted in the province and is determined by its development level: a province will gain 1 gold for every increase of 1 development level. The player can loot provinces they occupy or those which they are 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. A province will only begin to recover six months after the last successful looting, at a rate of 10% each month.

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

Looting greatly reduces the owner's tax income and unit construction speed, as well as increasing devastation (1.20 and onwards). Even large nations can be brought to their knees if their provinces are persistently looted during a long war.

Various ideas increase looting speed; this bonus increases the amount of ducats looted each month by the stated amount (and thus decreases the time taken to fully loot a province).

+25%
+20%
+10%
• Anatolian idea 3: Akîncî Cavalry
• Berber idea 5: Tuareg Cavalry
• Chickasaw idea 5: Slave Raids
• Shan idea 5: Raiders

### Attach to army

This action attaches the player's army to a friendly army, causing their 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.

### 焦土战术

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]

 −50% 本地敌军移动速度

Scorching the earth can be useful when the player's army is too weak military to fend off attackers and their 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. The player will lose income in the meantime, but if they were going to lose control of them anyway it could be a good idea 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.

### 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. During Age of Revolutions it is possible to enable Improved Force March ability, which reduces military power cost to 0 (requires Mandate of Heaven).

## Strategies and tactics

### Defensive wars

• Defending territory is easier than conquering it, and the bigger the battlefield the easier it gets.
• The player's enemies will want to besiege and conquer provinces, sometimes to the point where their armies become separated and easily dispatched by the player.
• 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, this may be bad for the player's economy, however.
• Sometimes they will also use hunter-killer armies to destroy the player's 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 the player's main army is bigger than the enemy's hunter army, it is recommended to destroy the hunter army 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 the player's forces are inferior to the enemy's hunter army, the player can try to evade it and focus on killing siege armies. This will force the enemy to split up its 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 its armies can not move.
• Besiege its 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.
• Keep in mind that if they have a high number of mercenaries, manpower won't matter as much to them. However, this, in turn, means they're much more reliant on income to prevent attrition; if they're running low on cash, or you can easily blockade/besiege some of their richest provinces, a mercenary-heavy army will still fold.
• 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.

### 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).

 陆战 陆军 • 陆军单位 • 训练度 • 人力
 海战 海军 • 海军单位 • 水手
 其它 宣战理由 • 厌战度 • 军事传统 • 将领 • 军事同盟