The smallest military unit is called a cohort. A cohort is comprised of 500 men, and multiple cohorts can be grouped to form an army.
All units types have the same basic stats:
- The strength of a cohort represents the number of men that it currently has. All cohorts are raised at the maximum strength of 500, equivalent to the 500 manpower it costs to build.
- Cohorts that lose strength through battle or attrition can use manpower to restore strength. For instance, a cohort at 400 strength will cost 100 manpower to fully reinforce.
- The replenishment time it takes for a cohort regain full strength depends on various factors, particularly whether it in friendly, neutral, or enemy territory as well as the cohort's reinforcement speed modifier.
- All cohorts have a base of 3 morale, which determines how much damage the cohort can take in battle before it retreats.
- Each cohort has a certain amount of experience from 0% to 100%, which reduces damage in combat and can be gained from fighting, sieges, and starting experience from buildings and other modifiers.
List of unit types
There are 11 types of land units. For levies, these are automatically assigned based on the culture of the levied pops. Legions have their cohorts individually selected and trained at the cost of manpower and money. Note that engineers can only be raised in Legions.
|Unit type|| Monthly
|Archers||8||45||0.24||none, always available||✔||2.5||2||+30%||−10%||5%||2.4||0.1|
|Chariots||8||45||0.24||Military tradition: Barbarian or Indian||✘||2.5||1||5%||2.4||0.2|
|Horse Archers||16||60||0.58||Steppe Horses||✘||4||5||+25%||+50%||5%||3||0.25|
|Light Infantry||8||30||0.24||none, always available||✔||2.5||1||−30%||−50%||2.5%||2.4||0.1|
|Supply Train||20||120||0.66||none, always available||✘||2.5||1||+100%||10%||50||0.05|
|Engineer||40||120||0.66||none, always available||✘||2.5||1||+100%||10%||5||0.05|
Unit type combat effectiveness
- Siege assault: Whether this unit type can assault forts.
- Movement speed: Speed on the map. (Armies move at the speed of its slowest unit.)
- Maneuver: How many squares away this unit type can target an enemy on the Battle chess board. Units with 1 maneuver can target one of the 3 squares in front of them, while elephants with 0 maneuver can only attack one, directly ahead of them.
- Morale damage taken: Affects how fast the unit flees from combat. Also affects caused morale damage (scales with unit's morale)
- Strength damage taken: Affects how much manpower will be lost in combat. Also slightly affects all caused damage (scales with unit's strength).
- Attrition weight: Multiplier that is applied on the base army weight per cohort (1). An army will take attrition if its total army weight is higher than the supply limit in the territory.
- Attrition loss: Percentage of the cohort's total (not current) strength lost if its army runs out of food.
- Food storage: How much food one cohort of this type can carry.
- Food consumption: How much food one cohort of this type consumes per month.
- Unit type icons: Multiplier for caused damage against that unit type.
Modifiers to unit types
- Discipline: Increases damage caused.
- Terrain bonus: Increases damage caused when fighting in a specific terrain type.
- Offense: Increases damage caused.
- Defense: Reduces damage received.
- Morale: Increases morale damage caused and makes the unit stay longer in combat.
- Maintenance: Reduces upkeep costs, for legions and mercenaries.
- Starting experience: Increases initial experience when recruiting or raising this unit.
Certain types of cohorts are support units. Support units are very ineffective in combat generally only make up a small proportion of the army, but have important roles and bonuses for most of an army's other functions and needs, such as with logistics, movement, and sieging.
Supply trains carry by far the most food of any cohort type while consuming very little themselves, and for most armies will make up the majority of their food storage. As the rate at which an army resupplies in friendly territory is based on its maximum food capacity, supply trains also indirectly increase their rate of resupply. In levies, 1 extra supply train is raised for every 9 cohorts in the levy, over and on top of all cohorts raised normally (this means that larger levies will always be a little bit larger than their base strength).
In general, supply trains are required for most armies to operate in enemy territory for more than a few months at a time without taking heavy losses from attrition, which is particularly important when engaging in prolonged sieges.
Engineers represent units specialized in sieges and the construction of military facilities such as siege towers, roads, temporary bridges, and more. While expensive, they provide significant support for sieges and army movement and can significantly speed up the prosecution of a war. Engineer cohorts are available only to legions.
For instance, 4 engineer cohorts will give +2 to the siege roll against a territory with 1 fort level, but only 1 against a territory with 2 fort levels. Engineers generally become less efficient as the strength of a fort increases, but can reduce smaller and weaker forts quickly.
Having at least one engineer cohort in an army reduces the cost of building roads (including military roads) to 10 gold (from a base of 50 for normal roads and 25 for military roads). This cost is not affected by any modifiers or by the number of engineer cohorts, as long as there is at least 1. The reduction in cost is very significant, even for military roads, and any legions that are assigned to building roads would benefit greatly from an engineer cohort.
An army that has at least 1 engineer cohort for every 10 cohorts in the army will also not take any combat penalties when crossing a river or strait, which improves the army's ability to maneuver and seek out favourable opportunities for battle.
Unit type strategy
Based on the various bonuses and penalties, each unit type seems to fall into certain categories.
These are not combat units. Their only ability is to have a lot of food capacity, in case attrition is a major issue. But, they seem to count for calculations of Cohorts for sieges. When looking at units' strengths, there is no point including this one. It takes +100% and deals −90% damage towards everything. If it is deployed to the battle, you may need more units to put in the front line.
Their high price means they should be deployed in moderation, but the long duration for them to fill up with food means they should not be deployed too late either.
There are only a few good things you can say about light infantry. While every other unit has some unit they counter, light infantry only has some units they are not too heavily countered by:
- They are cheap, with the same price Level as archers and chariots. They have a incredibly low attrition weight. Both this and the gold price makes them ideal if bodies rather then quality are needed, like for sieges. However even here, archers might be better in all but the most extreme cases.
- They have a lot of buffs from trade goods (leather and base metals) and a fair share of military traditions.
- A decent amount of combat tactics also have a high efficiency for them.
- While they take −25% morale damage, that barely offsets them taking around +25% morale and strength damage from every enemy. That also means they churn through more manpower in battle than perhaps any other unit.
- They can be used to "pad out" the side of the front line, to avoid the enemy being able to fully use flanking. This is a rare case where the reduced morale damage could be useful, despite the cost in manpower.
- They also have a lot of damage penalties. Their only hope seems to be to outlast the enemy on the morale front. They could also outnumber the enemy on sheer cohort count 1:2 at comparable prices − except manpower of course.
- Camel cavalry are the only thing they can claim to counter somewhat.
The first step up from light infantry and a mainstay of many armies.
- Their increased morale damage makes them more likely to flee, but such a behaviour can conserve manpower and make room for the 2nd tier cohorts − ideally things countering whatever drove off the archers. They are supposed to deal damage, but fall back to let others deal damage if they are countered.
- They do well against heavy infantry, at a fraction of the cost, as long as they outnumber the enemy.
- Not a lot of combat tactics make good use of them.
- Heavy and light cavalry in turn counter them heavily, but again they can quickly disengage due to extra morale damage without taking too many losses.
Old technology from the Bronze Age, they are largely outdated by the time of the game and accordingly only used by few:
- Only available to barbarians and a few other military traditions.
- The poor man's heavy infantry. If you lack the resources or the supply for those but have them available, they are a viable alternative.
- Strong versus archers and light infantry, extra countered by heavy infantry and heavy cavalry. Cannot assault in a siege.
- Can deal a lot of damage, but also take a lot.
- As cheap as light infantry and archers.
The mainstay of civilised and barbarian field armies of the period, but often hard to get:
- Requires Iron, a rather rare trade-good in some areas. Chariots are usually an alternative in those cases.
- They also cost a lot of supply and money, making them primarily useful in very favourable terrain with high Civilisation.
- Archers and horse archers counter them, along with elephants. Most other unit types have a poor match-up.
The ultimate melee unit, with a very high price to match. In almost everything the antithesis of the light infantry:
- Extremely expensive in money, supply, food and even time
- The ultimate first line in the game
- They barely take any strength damage and deal a lot of damage in return
- Strategies that affect them tend to have more effect then on any other unit type, with Shock Action giving a unmatched 200%.
- One-on-one, there is no unit that has any hope of countering them.
- The main counter is to outnumber them, especially with horse archers.
- Heavy infantry. light infantry and archers can also be counter options, since they don't have as high penalties to attacking elephants as others.
- Supply might be their worst enemy.
Coming out of the Bronze Age, riding horses became a major factor in warfare:
- Almost as cheap as archers and light infantry.
- Very high maneuver, with easily available horses. Usually the first flanking option one can find.
- Quite deadly against archers and the only counter to horse archers, making them a possible 1st Cohort option.
- Very good and very available flanker.
- Best movement speed in the game, making them useful for quick reaction forces.
The light cavalry of the desert regions.
- Usage is almost identical to light cavalry; refer to section for the basics.
- More expensive in gold.
- Inferior combat bonuses, but also penalties.
- Comparatively good supply, food storage/consumption and high maneuver.
Putting armor on horses and riders results in totally different usages:
- Available along with light cavalry, but uses are utterly different.
- Works nothing like any other cavalry units, more like a heavy infantry variant.
- Worse maneuver than light cavalry, well suited for the front line.
- More expensive in supplies and money.
- Stronger than heavy infantry against archers and most cavalry.
- The primary counter is heavy infantry, but horse archers are able to outlast them.
- Pretty good movement speed can give them a place in reaction forces.
Combines the best parts of cavalry and archers:
- In bonuses, penalties and stats, it uses the better of archers or light cavalry.
- In money and supply, it is the same as heavy infantry.
- Counters heavy infantry, but countered by light cavalry, camels and, potentially, elephants.
- The ultimate maneuver/flanking unit.
These are a special unit type, composed by Light infantry, available only to migratory tribes. Migratory units are created in the territory tab at the cost of 8 stability (this value can be modified by laws and by lowering centralization level). Migratory units can move across borders without military access and can settle in uncolonized lands or in occupied enemies' territories.
Migratory units, beyond settling, can perform two specific actions in non-owned colonized territories where they are standing:
- Raze: at the cost of +2 aggressive expansion, civilization in the territory will be reduced by half and the tribe gains advancement in each technology field equal to the amount of civilization razed divided by 10 (e.g. razing a 44 civilization territory will reduce civilization to 22 and give +2.22 technology advance in every field). The razed territory gets the Razed! modifier (−0.01% monthly civilization change) for five years.
- Pillage: Available only in territories with at least 20 civilization level. The tribe gets an amount of political influence and gold. The pillaged territory gets the Province Pillaged modifier (-0.25% local population growth, −25% commerce value) for five years.
If these actions are performed multiple times against the same country, reducing their opinion to -200, the migratory tribe will automatically declare war on them with the Show Superiority casus belli.
Migratory units can be merged with regular units but can't be raised during war.
Cohorts are not politically neutral in Imperator. In fact, they have many important implications in a state's politics.
- Cohorts can become loyal to a general personally, rather than to the state. While this decreases their maintenance costs (as the general is paying part of the expenses), loyal cohorts can be regarded as the general's "private" army. This is especially crucial if the general is disloyal and the state is in danger of civil war.
- In tribal states, clan retinues are always loyal to their respective clan chiefs. Clan retinue size decreases as centralization increases.
- Generals and clan chiefs gain power base and prestige based on the number of cohorts commanded and loyal to them personally.