In Imperator:Rome, an army represents a portion of the military power of a state. Historically, Rome referred to an army as a legion. An army serves as a container for cohorts and is represented by a pawn on the map that can be moved around on its own. War is waged with armies.
Armies can be created/destroyed/reorganized at any time for no cost by moving cohorts around.
However, if an army has a disloyal commander, they will refuse to give up their command and will refuse any reduction in their army's size. Also note that an army's size can have an effect on commander loyalty. Give a character a large military force, and you're giving them power. This personal source of power can then make them less loyal to the ruler(s) of their country, and potentially add to the list of characters contributing to a potential civil war. You might wind up giving command to a character with seemly reasonable loyalty, only to have that power go to their heads and see their loyalty fall; then be unable to remove them from command. Be cautious. Once your country has a large military, do not unify it under a single commander; have several.
What we call unit-abilities in Imperator can be one of three categories:
- Create New Unit - Allows you to create a new unit and transfer cohorts/ships to it, or back.
- Consolidate - Merges manpower depleted cohorts of the same type, and then removes empty cohorts.
- Detach Siege - Leaves behind a large enough force to siege or occupy the current city.
- Split Half - Splits the Unit in Half.
- Recruit To - Opens up the recruit window, so you can recruit cohorts/ships directly to this unit. They will automatically march and merge to this unit.
- Disband - For when you don’t want that unit anymore. This action has a one-time high monetary cost.
- Select Objective – Can select an objective for this unit, and it will perform it without further input from you.
- Select Tactics – Affects combat effectiveness in certain circumstances (see Combat Tactics)
All actions require that the commander, if any, is loyal.
- Allow Attachment – Allow other units to attach to this one.
- Attach/Detach to Unit – Attach to another unit present in the same territory, or detach once attached. The attached army will follow the army it's attached to without further input.
- Build Road – Causes the army to build roads while moving. There are two types depending on military traditions; for details, see Buildings § Roads.
- Drill Army – +33% maintenance cost and +100% loyalty gain chance in exchange for +2.5 monthly experience gain. The army cannot move, fight or siege while drilling. Requires a commander and normal or increased army maintenance. Not available for armies containing clan retinues.
- Force March – −100% morale recovery and +50% supply weight in exchange for +50% movement speed.
- Unit Reorganisation – +100% maintenance and −33% movement speed in exchange for +25% reinforcement speed and +10% morale recovery speed. Can only be done in friendly (owned, allied or subject) unoccupied territory.
All actions require that the commander, if any, is loyal.
- Anabasis – The ruler, commanding the army, visits the capital of a province other than the capital province. This increases province loyalty by 5% for (unrecognized string “pol” for Template:Icon) 15 political influence. Only available to monarchies every 2 years per province.
- Construct Border Fort – Builds a level 1 fort in border territory for 3000 manpower. This can be done in unowned territory to gain ownership of it, which also creates a freemen pop of primary culture and religion. Requires an Italic military tradition. For details, see Buildings § Border forts.
- Desecrate Holy Site – Destroys a holy site in a controlled territory for 2 aggressive expansion, angering followers of its religion and weakening its owner.
- Military Colonies – Creates a freeman pop of primary culture and religion in a territory with no more than 5 pops in a loyal province for 3000 manpower, 15% province loyalty, and loyalty for a random cohort in the army (or 1 tyranny if the commander is the ruler of a non-republic). Requires a tradition from the Greek, Levantine or Persian trees and an army with at least 5 cohorts with a loyal commander.
- Order Full Retreat – Gives the order for the unit to perform a shattered retreat from foreign territory or a battle. This is handy if you want to save the remnants of your army trapped deep in enemy territory, or when you are cut off by hostile forts.
- Pillage – Gain (unrecognized string “pol” for Template:Icon) political influence equal to one eightieth of the territory's civilization value (minimum 1) and (unrecognized string “treasury” for Template:Icon) 2.4 gold per pop or per cohort, whichever is less. This adds the “Province Pillaged” modifier for 5 years, giving −25% population growth and −25 local commerce value, as well as −20 opinion, which can stack up to –200. This is a hostile act and, if the victim's opinion is less than −100 before pillaging, declares war on the province's owner with the “Superiority” wargoal if they are not already at war. The territory must have a civilization level at least 20, have at least one pop, be a city or the province capital, be occupied if it has a fort, and not have been raided in the last 5 years. Only available to Migratory Tribes.
- Raise Levies – Raise a cohort from each owned and controlled territory in the province. They are light cavalry if horses or steppe horses are available, or otherwise light infantry. This costs 2 tyranny and a modifier “Increased Tension” giving +2 local unrest for 5 years in each affected territory, and reduces the army's morale by 25%. Each territory can raise a cohort only if it doesn't have this modifier. Requires military traditions from the Celtic or Persian trees.
- Raze City – Halve the civilization value in a city or province capital, converting it to research progress equal to one-eighth the value lost for each research category where the army's owner has fewer advances than the victim, in exchange for 2 aggressive expansion and −20 opinion, which can stack up to −200. This is a hostile act and, if the victim's opinion is less than −100 before razing, declares war on the province's owner with the “Superiority” wargoal if they are not already at war. The territory must have a civilization level of at least 5, have at least one pop, be occupied if it has a fort, and not have been raided in the last 5 years. Not available to tribes.
- Root Out Pirates – Remove the "Pirate Haven" modifier from an owned province that has it. Enabled by a law (not available to tribes).
- Settle – Colonize a territory, or seize it from another country after occupying it, and convert each cohort into a Tribesmen pop of primary culture and religion. If conquering, there must be more cohorts in the army than pops in the territory. Migrants can also be converted to pops in owned provinces. Only available for migrant armies in a migratory tribe.
- 参见：Supply limit
A constant factor in warfare are the non-combat related losses in a conflict. Armies moving through hostile territory, or areas unable to support them in general, may suffer as many casualties as armies directly involved in combat.
In Imperator locations have a supply limit (shown as a value next to the cauldron in the screenshot above), which is the size of army that the land can support without suffering attrition. Base Attrition is shown by the Skull in the province interface above.
Weather and hostile terrain can also directly increase attrition of present armies. An army in a desert city will always suffer 1% attrition from it, as will armies in locations with harsh winter or embarked on ships. Together with the mountain passes, roads and other features of the map this means that you will have to pay closer attention to the map when on campaign. Minimum attrition means that an unsafe route might be more punishing than what you are used to.
The automatic path-finding will prefer shorter movement times and low attrition when possible, but at times you might want to cross that desert to reach the battlefield you want.
Attrition ticks on the 1st of every month. If an army is in transit and arrives somewhere on the 1st, it will get attrition based on the destination.
The attrition weight of an army is equal to the the accumulated values for all cohorts it is comprised of plus modifiers. The value is compared to the current supply limit of the city the army is located in.
Armies moves from one city to another city. Adjacent cities have a calculated distance between them and armies move a base distance per day (subject to modifiers). The movement cost modifier increases the amount of time needed for an army to move from the territory to another territory, while the (unrecognized string “movement speed without road” for Template:Icon) army movement without roads modifier affects only the movement speed of armies if there is no road connecting the two territories.
Unit objectives allow you to assign individual armies orders to act autonomously under the control of the AI. Unit objectives are a way to outsource the management of some armies to the AI, essentially using the same things that the AI itself uses to control its armies and navies. You can at any time select an objective for each army or navy under player control (or several units at once, in which case the objective applies separately to each one currently), which enables AI for said unit, making it automatically take actions almost as if it was controlled by an AI country.
- No Objective: The unit remains idle unless ordered by the player. This is the default for players.
- Independent Operations: The unit acts independently, attacking enemy armies/navies, occupying enemy cities, etc. as it sees fit.
- Naval Landing: If there is at least one available and sufficiently large navy which has Naval Landing selected, ordering an army to move to a city that's accessible only by sea will make this navy pick up that army and ship it to that city. (Armies will default to traveling by land if a land route is available however, ctr + click order and the army will be transported by sea instead)
- Defend Borders: The army will stay inside friendly borders, fighting enemy armies that enter and retaking occupied cities.
- Hunt Fleets: The navy will seek out enemy fleets and attempt to engage them.
- Fight Rebels: Army will focus on destroying rebel (slave revolt) armies and retaking rebel-occupied cities.
- Reconnaissance: Patrols across the country's borders or nearby seas reporting enemy movements.
- Keep in Reserve: The army will stay within the country's borders and actively avoid contact with the enemy unless superior.
There are also many Unit Objectives that you cannot pick but that you may still encounter. Disloyal Generals will make use of a specific unit objective where they essentially do what they themselves want to. Making you unable to order them around or do things like send them to a certain death. Likewise Mercenaries that you do not pay will stop taking your orders and operate on their own. There is also special logic for Slave Revolts, where rebel stacks will seek out the closest rich city to attempt to loot and set free more of their kin.
In Imperator, Mercenary armies are always present, spread out over the map, using their own banner and the unit graphics of the local culture. As long as a mercenary army is not hired by anyone, it will also not count towards the supply limit in the city they are located. Mercenary armies all have their own General, to whom all the troops are loyal.
At times, Mercenary groups played a decisive part in conflicts, as did their tendency to abandon an employer that could not pay them.
Although expensive, mercenaries are useful for two reasons. Firstly, they do not use your manpower to fill their ranks. Secondly, many mercenaries have generals with high martial skills, giving you an advantage on the battlefield.
Mercenary Overview Screen
Here, you can at all times see what Mercenaries exist (sorted by Proximity) and who has hired them. It also displays the monthly cost of employing each Mercenary group.
Hiring a Mercenary regiment comes at an upfront cost of 100 gold and obliges you to pay their upkeep for the duration of their employment at a base rate of 200% the normal maintenance cost of the units.
Hiring mercenaries immediately brings them under your control, but does not move them to your territory. Hired mercenary armies outside of your territory will begin in a state of exile and must be moved to your territory before they can used in battle. Mercenary armies start with 0 morale and 0 food, so they must be hired ahead of time.
Any Mercenary company in diplomatic range can be hired as long as you can afford to pay them, but their high upkeep means that hiring an army far from your conflict could get expensive as you would be paying their upkeep from the day they are hired.
Once no longer exiled, the mercenary army will act as any other army under your control, except for the fact that you cannot remove their leader or remove any units.
As with any army, you can also disband a mercenary army at any time it is not in battle. However, their increased upkeep cost will also mean that disbanding them can be quite costly.
Once disbanded, the mercenary army will again be considered available for hire, and it will begin its journey back to its home location.
Sometimes, disenfranchised heirs may supplement the Mercenary company list.
Should you not be able to pay your mercenaries, several negative consequences may arise. For instance, that mercenary band might offer to join the opposing side in an ongoing war.