This article may contain outdated information that is inaccurate for the current version of the game. It was last updated for 1.8.
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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 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.
- 1 Combat interface
- 2 Deployment
- 3 Combat sequence
- 4 Combat statistics
- 5 Terrain
- 6 Sieges
- 7 Mechanics of an Army
- 8 Strategies and tactics
- 9 See also
- 10 References
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.
- Main article: Army#Composition
To maximize the effectiveness of an army, a proper mixture of troops is important.
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. 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||0||2||5||6||8||11||14||16||18||20||22||24||26|
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.
|Terrain||Mountains||Hills, Jungle and Marsh||Forest and Woods||Plains, Grassland, Desert and Coastline|
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.
This section may contain outdated information that is inaccurate for the current version of the game. The last version it was verified as up to date for was 1.1.
[This section's factual information is debatable. See the discussion page for more information]
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:
- Deploy all infantry in first row.
- Deploy as much cavalry at the sides of the first row.
- 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.
- 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:
- Deploy all infantry in first row, except for X[Unknown value] positions to each side.
- Deploy X units of cavalry to each side in the first row.
- Deploy all artillery in the second row.
- 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.
- Deploy all remaining cavalry in the second row, beginning from the edge and going inwards.
For the bigger army
- 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.
- Deploy all cavalry in the first row that can be positioned to attack the enemy units in the first row.
- Deploy all artillery in the second row.
- 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.
- 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.
When two warring armies meet in a province a battle will commence. A battle will last until one side is routed or annihilated.
The attacker gets +0.5 Morale upon starting a battle. This can take them above their Morale maximum but only until the end of the battle.
Combat is divided into a series of 3-day phases. Phases alternate between Fire and Shock, with the Fire phase happening first.
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.
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:
die result = die roll + attacking leader skill + attacking unit attack pips - defending Leader skill - defending unit defense pips - terrain modifiers
- Die roll: A random number between 0-9, rolled for each entire side at the beginning of each phase (not each day).
- Leader skill: The leader skill for that phase (Fire or Shock).
- Attacking unit attack pips: 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: Harsh terrain may give a penalty to the attacks of the attacking army.
Casualties caused by each unit during each day are computed as follows:
casualties = base casualties * attacking unit strength * attacking unit modifier * (100% + attacking unit Combat Ability) * attacking unit Discipline / defending unit Tactics
- Base casualties: Base casualties is determined by the die result according to the following table:
Die result -2 or less -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 or greater Base casualties 4 8 12 16 20 24 32 40 50 60 70 80 90 100 100 120
- Mean casualties for a particular attacker advantage (net modifier to the attacker die roll) are as follows. Marginal proportional increase is the ratio of that entry compared to the last.
|Mean base casualties||4.0||4.4||5.2||6.4||8.0||10.0||12.8||16.4||21.0||26.6||33.2||40.4||48.2||56.6||64.6||74.2||83.0||91.0||98.0||104.0||109.0||113.0||116.0||118.0||120.0|
|Marginal proportional increase||0.0%||10.0%||18.2%||23.1%||25.0%||25.0%||28.0%||28.1%||28.0%||26.7%||24.8%||21.7%||19.3%||17.4%||14.1%||14.9%||11.9%||9.6%||7.7%||6.1%||4.8%||3.7%||2.7%||1.7%||1.7%|
- Attacking unit strength: If the attacking unit has below its maximum of 1000 men, damage will be reduced proportionally.
- Attacking unit modifier: The attack modifier from the attacking unit's technology, e.g. "Infantry Fire".
- Attacking unit Combat Ability: Any Combat Ability bonuses the attacking unit has.
- Attacking unit Discipline: The Discipline of the attacking unit. Note that Discipline does not currently help in defense.
- Defending unit Tactics: The Tactics of the defending unit.
morale damage = base casualties * 0.01 / 6 * attacking unit strength * attacking unit maximum morale * (100% + attacking unit Combat Ability) * attacking unit Discipline / defending unit Tactics
- 6 base casualties translates to dealing 1% of the attacking unit's maximum morale as morale damage. Note that the modifiers may be different.
- Attacking unit maximum morale: Note that this is the maximum morale of the attacking unit, not the current morale.
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.
- Base: 0.50
- Military Tech (4): +0.25
- Military Tech (6): +0.25
- Military Tech (7): +0.25
- Military Tech (8): +0.25
- Military Tech (15): +0.50
- Military Tech (19): +0.50
- Military Tech (23): +0.50
- Military Tech (30): +0.50
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.
Morale is an important factor in fighting battles. Each turn of combat a unit will take a Morale hit. 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.
A unit that has its morale drop below a certain threshold 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 to a certain point.
If an army loses a battle while having low enough morale to be disorganized, they will be forced to retreat to a safer province often much further away than just one over – it could be two or three provinces from where the battle was fought. They will usually retreat to one with a high base tax value, forts, and no adjacent enemies. While retreating, it cannot be engaged in combat or be controlled until it reaches the safer province. The army also moves slightly faster, and will recover morale at a normal rate during the retreat.
After every battle is fought an army must spend some time not fighting for its morale to recover.
- A shattered army will get an extra morale bonus as it stops retreating.
- Morale is not gained while forced marching
The following contributes to the maximum morale of a nation's army.
- Army Maintenance: Ranging from 20% at minimum maintenance to 100% at maximum maintenance (multiplicative modifier)
- Ideas and policies:
- 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)
- Prestige: +20% at 100 Prestige, -20% at -100 Prestige
- Army reformer advisor: +10%
- Army tradition: +25% (at 100 tradition)
- Being the Defender of the Faith: +5%
- Piety (Muslim only): +25% (at 100% Piety)
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.
|Technology group||Western||Eastern||Ottoman||Muslim||Indian||Chinese||Nomad||Sub-Saharan||New World|
Flanking range determines the horizontal range in which a unit may make a flanking attack. 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 50% flanking range. When between 25 and 50% strength they will fight at 25% of their flanking range. The final range is always rounded down to the nearest integer. The base flanking range is 1 for infantry, and 2 for cavalry and artillery. There are technologies which increase flanking range of your units as the game progresses.
Terrain used to be randomly selected, but since the latest expansion, is now static to each province. Entering a battle in rough terrain will incur a negative modifier to the attacking army, with each terrain having a different modifier. 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.
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 will be protected by rivers.
- Crossing a strait: -2 to all rolls.
- 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.
When your troops enter an enemy province and are not moving into another province, a siege will begin. To progress in a siege, you need at least as many besieging troops as the enemy garrison. It does not matter which unit type the besieging units are, but only infantry can try to storm the enemy fortress. Progress in a siege will never decrease as long as attackers are continuously present; however, if all attackers leave, it will be instantly reset.
Besieging armies will always take at least 1% attrition.
A siege progresses in phases. Each phase has a base length of 30 days, modified by the defender's Fort Defense ("defensiveness" in the game files).
The mean number of phases to finish a siege for a particular starting bonus is as follows:
|Starting success %||-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%|
|Sieges per year||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|
"Sieges per year" is computed at the default phase length of 30 days.
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.
- Leader siege. If the attacking army has a leader, the leader's siege skill is added as a bonus.
- Leaders can have Siege, capped at 6. Getting the maximum Siege 6 with no leader Siege bonuses is possible, but the chance seems to be less than one in a thousand.
- The Inside Man event can increase leader siege by 1.
- The Engineer Corps idea (Defensive Ideas) increases leader siege by 1.
- The Army Sappers unique Idea (Netherlands) increases leader siege by 1.
- Artillery. A bonus depending on the ratio of their Artillery to the defender's Fort Level:
Modifier Artillery per Fort Level +1 Any artillery at all +2 At least 2 artillery per fort level +3 At least 3 artillery per fort level +4 At least 4 artillery per fort level +5 At least 5 artillery per fort level
- Blockade. If the province is coastal and not blockaded, a -1 penalty is applied, with an additional -1 if the defender owns the province (?)
- Fort Level. The defender's Fort Level is applied as a penalty.
- Walls Breached. A +3 bonus is applied if the defender's walls have been breached.
The highest possible starting bonus is thus +6 for the leader, +5 for artillery, and -1 with Fort Level 1 for a total of +10.
The die roll may result in an increase of the siege status, to a maximum of 12. This improves the results of future siege stages.
|5 - 11||Supplies Shortage||+1 siege status|
|12 - 13||Food Shortage||+2 siege status|
|14 - 15||Water Shortage||+3 siege status|
|16 - 19||Defenders Desert||+1 siege status, reduces garrison (?)|
|20 or more||Surrender||Siege successful|
Additionally, if a 14 is rolled on the die (before modifiers), the defender's walls are breached. This applies a +3 bonus to future rolls. Walls cannot be breached more than once.
Therefore, the attacker needs at least a net +6 bonus to have a chance of ending the siege. Since siege status and Walls Breached will eventually reach their combined maximum of a +15 bonus and the maximum Fort Level is 9, only non-blockaded coastal sieges can possibly fail to eventually succeed.
The attacker may choose to assault the garrison with their infantry. This results in a speedy conclusion of the siege at the cost of 5 Military power, and usually lots of lives. The attacker loses roughly 10 times as many men as the garrison if the walls are not breached and 1.5 times as many if they are (what else affects this?). Only infantry can assault.
Mechanics of an Army
- Main article: Army
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.
To loot an enemy province, move an army of any size into it so that it immediately starts a siege (it doesn't matter if there are too few troops to progress the siege). If it continues moving, it won't loot even if you then halt it. It also won't loot if it has to fight a hostile army first. Exiled armies can't loot (since they can't siege). A sieging army will also automatically attempt to loot the province it's in at the start of each month.
The owner of the looting army will instantly gain an amount of ducats equal to the province's base tax. This number is doubled for hordes. The province will gain the looted province modifier that lasts for a duration of 6 months and has the following effects:
- -10% Goods produced
- -50% Local tax modifier
- +30% Local recruitment time
- +30% Local ship building time
- +5 Maximum attrition
- -10% Supply limit modifier
You can loot a province if all of the following are true:
- You don't have a core on it.
- It's owned and controlled by enemies. The owner and controller don't have to be the same.
- It hasn't been looted recently (i.e. it doesn't have the "Looted" modifier).
- It doesn't border any province owned or controlled by you, a subject or war ally, or someone who grants you military access.
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 general with the highest ability scores will command the armies in battle. 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.
- See also: Colonization#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 will spawn immediately and must be defeated in battle to clear out the native population. This action costs military power and will permanently reduce the potential value of the province. The elimination of all natives in a province will prevent any future raids on the local colony or any passing armies.
- -50% Local tax modifier
- -0.33 Goods produced
- -50% Supply
- +25% Local defensiveness
- Monthly autonomy change +0.1
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.
Strategies and tactics
- 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.
- If the border is narrow (1/2 provinces) a March is worth building. March, Severe Winter and Scorched Earth can cause outstanding attrition that can easily burn the enemy MP pool, especially if the province is very big. The 200% bonus to defensiveness also makes sieges take three times as long (by increasing the length of siege cycles).
- 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 Scorch 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 one day from arriving, 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.
- 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.
- Military technology. More troops does not necessarily mean victory. How advanced these troops are matters too.
- Tech group. Usually Western troops, especially late game, are always better than Eastern/Ottomans/Muslim group.
- 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, Ottoman Empire and so on).
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 province being sieged---one artillery will give a +1 bonus regardless of Fort Level.
- 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.
- 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.
- Use leaders. Even a bad one is worth using.
- 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. Avoid it as much as possible. A 10,000 men army with 5% attrition will burn 500 men each month from your manpower pool.
- See in : BASE_COMBAT_WIDTH = 15.0