Imperator: Rome

Dec 14, 2019

Imperator: Rome marches on. Although we’ve mentioned some issues in our official review, one has to note the sheer number of nations that you can play as during the time period.Hundreds of. Imperator: rome 2.0 and re-release on 24th of november? Crusader Kings III Available Now! The realm rejoices as Paradox Interactive announces the launch of Crusader Kings III, the latest entry in the publisher’s grand strategy role-playing game franchise. This community wiki's goal is to be a repository of Imperator: Rome related knowledge, useful for both new and experienced players and for modders.

If you've complained about how hard it is to expand quickly, then this guide is for you. We'll look at how warscore and aggressive expansion works, and how to get the most land for lowest cost in Imperator: Rome 1.3.


Fabricate as many claims as you can and ALWAYS turn them into a vassal (can be any type). These combined lets you expand for 25% of the aggressive expansion and warscore.
You can easily provoke your vassals into rebelling by using Harsh Tributes button in the economy screen (works on every type of subject). This will let you take all their land for free. The only downside being you have to fight them twice.
Very important note: subjects of your Culture Group will never rebel against you.

Mechanics Summary

When conquering it's important to note the following things:
  • War Target means the country you declared war on.

Annexing Land


Base Costs
  • +1 base.
  • +5 if a port.
  • +1 for every 5 pops (if city).
  • +1 for every 2 buildings (if city).

  • +10% has pops of your culture.
  • +10% has pops of your religion.
  • +33% not war target (aka the allies or subjects of the country you declared war on).
  • +300% show superiority wargoal.

up to +2500% depending on how small a country is:

  • -10% bellicose diplomatic stance.
  • -25% take province wargoal (can only get this if you're the attacker).
  • -33% claim on territory.
  • -25% for each rank difference lower than war target (lowest is local power).

This means if you're a local power or city state fighting a great power, you get a -75% discount on all of the great powers provinces:
  • -95% rebelling province.

Aggressive Expansion

Base Costs
  • +1 base.

Imperator: Rome Battle

  • +33% not war target.
  • -0.5% for 1 tyranny each.
  • -50% claim on territory.
  • -100% rebelling province.

Vassalising countries
Turning someone into a vassal takes all the costs above and halves them. So instead of needing 100 warscore and taking 100 aggressive expansion, you only need 50 warscore and take 50 aggressive expansion.

Conquest Strategy

Very important note: subjects of your Culture Group will never rebel against you.Imperator:

Conquering Foreign Lands

Expanding through vassalising is a lot cheaper than direct annexation. Combining claims with vassalisation lets us conquer at 25% the cost. Using this strategy as Macedon, you can turn Egypt into a tributary who will never rebel.
Allies of the war target are 33% more expensive to conquer. It's best to fight the biggest nation head on, rather than declaring on smaller allies.Imperator rome forum
Attacking nations of a higher rank than you are also much cheaper in warscore. If you're about to go to war with a higher rank enemy, it may be worth reducing your rank by giving land to a subject or client state.
Aggressive Expansion doesn't care how valuable a province is. Taking a 1 pop desert territory costs the same as taking Rome or Carthage. It's more efficient to expand into high value provinces rather than empty land. However civilised lands tend to have much lower happiness than tribesmen.

Annexing Vassals

Once you've acquired enough subjects, it comes time to trick them into rebelling so you can annex their lands for free. You can do this by setting Subject Tributes to Harsh in the economy screen.
A subject must be lower than 33 loyalty to rebel. If they're still above that, send them an insult.
You can check a list of your potential rebels by looking at the rebellion threshold in your country screen. You can also check each subjects loyalty by going to their country in the diplomacy screen.
Once they rebel, conquer them again separate peacing each rebelling country for all their land. Be sure to conquer the war leader last, as otherwise you might not be able to afford all the land in warscore.

Conquering Lands of the Same Culture

For these guys, it's better to claim & directly annex rather than subjugate, unless you really want permanently loyal vassals. Just remember that it's very expensive to take land that belongs to the allies of the war target.

Managing Unrest in Conquered Lands

Aggressive expansion is probably the greatest limiter to expanding in Imperator Rome. For each point of AE, you get the following maluses:
  • -1% wrong culture group happiness.
  • -0.5% wrong culture happiness.
  • -0.02 claim fabrication speed.
  • -0.5 subject loyalty (33 is the loyalty threshold).

Imperator: rome cheatFor each point above 50 AE
  • -0.5% primary culture happiness.
  • -0.1% monthly political influence.
  • -6% aggressive expansion impact (this is a bonus).

Above 66 aggressive expansion, conquering new provinces is basically free. However it is nearly impossible to maintain this. Any foreign culture pops will have zero happiness, zero output, and max unrest. At that point, conquering any foreign cultures is just adding liabilities that will rebel in your country.
A pops base output is their happiness. A pop at 25% happiness will produce at 25% output.
Any pop below 50% happiness generates unrest. Unrest hurts religious conversion and cultural assimilation speeds MASSIVELY. If a territory is above 4 unrest it will stop converting/assimilating entirely. It also lowers provincial loyalty and outputs, but less significantly.
In short: high AE = low foreign output, high unrest = low conversion / assimilation speed
However it is possible to maintain low unrest with high AE, allowing us to circumvent the AE happiness debuff. Without going into too much depth, you can assign leaderless armies to a Region with the provincial army mechanic. Depending on how many troops you have assigned, every territory in the region can receive up to -5 unrest. This will allow you to convert pops to your primary culture, and in doing so significantly raise their happiness.
Note: it's faster to convert then assimilate pops, than it is to assimilate then convert pops.
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If, like me, you simply cannot get enough of Paradox Development Studio’s grand strategy titles, then you have likely been playing a lot of Imperator: Rome. Though the game synthesizes mechanics gleaned from a bunch of the studio’s previous titles it is first and foremost concerned with warfare - expanding your empire, and winning battles. Because of this, a strong emphasis is placed not just on strategic geopolitics, but also on the nitty-gritty tactical-level combat of your armies in the field.

Whereas in some other Paradox titles tactics can be safely ignored, in Imperator, they’re a fundamental component in your quest to stamp your name across the map. It's not quite as impenetrable as some grognard fare, if you're new to these kinds of games, the minutiae of the new tactical combat mechanics can be a bit daunting. If you need a primer, or just want to see what’s changed in the recent 1.3. 'Livy' update, we’ve got you covered.

The Fundamentals

Let’s start with the absolute basics before moving onto the meatier stuff:

  • Armies are composed of cohorts of 1000 men each and are built and replaced using your nation’s available manpower pool.
  • There are nine unit types: Archers, Heavy Infantry, Light Infantry, Camels, Heavy Cavalry, Light Cavalry, Horse Archers, Chariots, and War Elephants.
  • Each of these unit types has certain traits — like their maneuver and damage ratings — that make them useful in certain roles, such as cavalry in the flanks, archers as frontline skirmishers, and heavy infantry as the hard backbone of your reserve. Units will also deal more or less damage based on what type of unit they are fighting.

It’s worth noting that Imperator is extremely transparent, although it's not always obvious. Pretty much everything you need to know to make informed decisions about your enemy can be found in tool-tips or other parts of the UI. For example:

  • You can see exactly how many cohorts other nations have recruited and how much manpower they have in reserve in the Diplomacy Screen.
  • The Warscore Screen will tell you how many of each unit type an opponent has.
  • By hovering your cursor over an enemy army, you can see what types of units they are comprised of, as well as their general’s martial skill.

Combat Mechanics

Imperator’s combat system is broken down into 3 components: a primary frontline, a secondary frontline, and flanks. It’s similar to the system Paradox used in Europa Universalis IV, though much more streamlined for tactical customization. Here’s how that system plays out in practice:

  • Only the units in the Primary frontline and the flanks can attack.
  • Units attack the enemy directly across from them at first, and then, as units flee or are killed, they can attack other units in the line based on their maneuver skill.
  • Flanking units typically have a high maneuver, allowing them to attack far into the primary frontline after the enemy flank has been dealt with.
  • Once units from the primary frontline are removed, units from the secondary frontline, acting as a reserve, will move into the line to take their place.
  • Both the size of the flanks, as well as which unit types will be placed in each of these roles can be modified in the Army Interface, allowing you to experiment with the different roles once you have a firmer grip on combat mechanics and army composition.

Additionally, discipline, morale, leader skill, and terrain all impact this basic structure. A die roll takes these factors, as well as your unit types and modifiers and applies them to determine how much physical and morale damage is being dealt, with a new roll happening every five days. Having a Leader with a high martial skill will give buffs to your rolls, whereas adverse terrain effects can give a debuff. Even if there is some hard math going on under the hood, you can get by with an intuitive understanding of some military basics.

For example, you don’t need a graduate degree in mathematics to know that you should avoid letting incompetent generals attack with underpaid units over rivers.

Army Composition, Traditions, and Tactics

The real nuts-and-bolts of Imperator’s tactical gameplay lies at the intersection between the various combat mechanics and each nation’s unique strengths and weaknesses. The trick to crafting a coherent army composition is to take into account how these systems react to and play off one another. So, how do you know what composition to use? Most often, this will be determined by three factors: resources, traditions, and tactics.

Army Composition: Resources

At the most basic level, resources will determine what units you can recruit. To build war elephants, for example, you will need access to an elephant resource tile. This effectively locks certain unit compositions away from certain nations until they expand enough to acquire these resources. Strategic resources like iron, steppe horses, camels, or the aforementioned elephants will be highly sought after, and will likely funnel your nation’s army composition in a certain direction based on what you have available to you.

Army Composition: Traditions

Equally as important as resources is your Military Traditions. There are seven unique tradition trees, each with three branching paths comprised of eight steps, representing broad ideological developments within a culture group. These provide bonuses to different unit types, unlock special military abilities, and some even grant access to unique tactics for your army to use. Much like the scarcity of resources, the bonuses provided by these military traditions will shepherd you towards some types of units and away from others. Do your traditions give significant buffs to cavalry? You should probably consider using a cavalry-heavy force with wider flanks. Tons of Elephant buffs in the tree you chose? Maybe a meatier shock-focused force is right for you.

Army Composition: Tactics

The next factor to consider when composing an army is tactics. There are ten tactics that you can select for your army: five basic (Shock Action, Envelopment, Skirmishing, Deception, and Bottleneck) and five that are unique to specific military tradition trees (Triplex Acies, Hit and Run, Padma Vyuha, Cavalry Skirmish, and Phalanx). The old Sun Tzu maxim “if you know the enemy and know yourself, you need not fear the result of a hundred battles” holds especially true here as these tactics operate in a Rock-Paper-Scissors fashion with each tactic of the ten being good against two, bad against two others, and neutral against the rest.

If you’re having trouble finding out which tactics to use, the tooltip on the left of each bar shows what the percentage of effectiveness is for each tactic option based on your current army composition, while on the right of the bar it shows what tactics each particular type is good or bad against. Of course, Combat is not only knowing what tactics to use, but also knowing what tactics your enemy is likely using based on their current composition. Even if a tactic is lower on total efficiency, it may be more effective based on the enemy army's composition.

Army Composition: In Practice

So, what does this look like in practice? Let's use Rome as an example to see how these three factors come together to provide the framework of an effective army composition. Starting with the first factor, resources. Elephants, camels, and horse archers are all out of your reach from a resource perspective, so you likely won't be able to use those, but Rome starts with access to iron and horses, so two types of cavalry, as well as heavy infantry are on the table.

In terms of traditions, Rome is part of the Italic military tradition, and within that tree there is a Roman branch that provides two bonuses to heavy infantry and one to light infantry. So you’re going to want to use mostly heavy infantry, with some light mixed in for skirmishing purposes, depending on your tactics, alongside some heavy cavalry, as the two starting tactics that buff heavy infantry — Bottleneck and Shock Action — also boost heavy cavalry.

Early on, you will be pulled towards the Bottleneck tactic, as it is effective with heavy infantry and cavalry, but the light infantry builds of your northern Gallic neighbors are likely using the skirmishing tactic, which is effective against that, so it may be a good idea to switch to shock action to neutralize. If you’re starting to expand south and begin fighting in North Africa and the Carthaginians are using shock tactics with elephants, switch over to the bottleneck tactic and change your composition accordingly. Once you have unlocked the Triplex Acies tactic from your traditions, switch your composition to a heavy infantry, light infantry, light cavalry combination to maximize efficiency and decimate skirmisher-reliant tribal states and the antiquated phalanxes of Alexander’s successors. Success in Imperator, much like Roman success in the real world, will depend on your ability to be flexible depending on what you know about your enemy.

Other Key Concepts

Forts and Terrain

Operationally, Imperator uses forts and terrain to create a complex landscape to play out these engaging tactical battles. Forts exert a zone of control that disables movement through adjacent provinces, forcing armies to stop and siege before proceeding. Where the nuance comes into play is when you combine this feature with the impassable terrain that dots much of the map.

Creating bottlenecks through alpine passes or ambushing divided armies taking circuitous routes to get around forts is extremely satisfying and makes for some nail-biting gameplay. By navigating these mechanics wisely, even outnumbered armies can make the most of a strong defensible position to defeat a larger foe or stymie an attempted conquest. Don’t haphazardly deploy these defenses, though, as forts are an expensive resource to maintain and take up valuable building slots in your settlements. Be sure to tear down forts on pacified frontiers and replace them with more productive buildings.

Attrition, Manpower, and Mercenaries

At the macro level, your ability to keep the war machine running is going to be determined by your available manpower. It’s the key resource you will need to sustain your conquests. Unfortunately, in many provinces, harsh attrition can melt away your manpower in a matter of months. In theory, even in your home provinces, Imperator’s brutally high attrition can prevent the kind of giant doom stacking that other Paradox strategy titles see, creating interesting tactical considerations in the process; however, by knowing how to get around these kinds of issues, you can avoid unnecessarily dividing your forces.

Some recent tinkering in the Livy update has made manpower even more vital. Maximum manpower caps have been shrunk and base manpower has been reduced by 50% from previous 1.2 levels. Along with a general decrease in starting army and navy sizes, this means that you have to make this already thinly-stretched resource go even farther. Avoiding unnecessary attrition is therefore a must for any competent strategist.

The best way to avoid attrition damage is to understand the new supply mechanics. While the 1.2 update added food as a new provincial resource that you need to manage, 'Livy' has added this mechanic to armies as well. To keep your stacks from taking unnecessary attrition, you can now rely on supply wagons that can be recruited as cohorts. These slow moving units are useless in combat, but allow you to bring stockpiled food with your troops to prevent attrition damage. Your armies can also raid food stocks from your enemies as well, allowing you to circumvent the brutal attrition of the ancient world.

What this means in practice is that you can maintain much larger stacks, so long as you are keeping up with your supply units. Make sure to keep these with your army to preserve your manpower. Doing so will allow you to focus the vast majority of your manpower on battlefield casualties, where it’s needed most.

The other key method to preserve manpower is to rely on mercenaries. Mercenaries are much more than a simple stopgap measure for wartime emergencies or auxiliaries to supplement your main army. The preciousness of manpower and the brutality of pre-modern attrition rates mean that they take on a much more pivotal role. In the early game, they will be less viable for smaller nations, as their high maintenance and disband cost (you need to pay them a lump sum at the end of their service) means that unless you’re playing as one of the large Diadochi kingdoms, chances are you won't have the income to use them outside of extreme emergency situations. In the mid-to-late game, however, mercenaries will become much more vital for your war effort. As your state expands, trade and tax income should leave you with a healthy well of cash to dip into. By converting this cash into what amounts to a secondary manpower pool, you can keep up the pace of pyrrhic wars or conquer small states while your manpower pool is replenishing.

Imperator: Rome - Magna Graecia

Mercenaries are spread out fairly evenly over the map, so there will likely be some in your backyard or your neighbors if you really need them. In the post-Alexandrian east, where the coffers are deeper, wars can often devolve into largely mercenary affairs, as each side tosses stacks at one another in order to overwhelm each other in the harsh deserts of the near east. If you find yourself on the wrong side of one of these conflicts, know that mercenary armies can be bought off and flipped to the opposing side of a conflict by being offered a large sum of money, which the original buyer can counter with a higher sum. This can allow you to significantly weaken an opposing enemy army right before an engagement or potentially end an important hostile siege. When it turns the tide of a close war, it feels so, so satisfying.

While the well-timed deployment of mercenaries can turn the tide decisively, it’s also worth noting that the last two updates have de-incentivized the overuse of this option. The introduction of supply and food mechanics slightly eases the necessity to rely on mercenaries to avoid Imperator’s crippling attrition. As long as you bring sufficient supply units, it’s possible to keep your manpower from melting away.

Additionally, recent increases in the cost of buying and maintaining mercenary forces makes them much more costly than they were at launch. To purchase them, you not only need to sacrifice valuable gold, but also Military Experience, the resource that you need to get access Military Traditions. The Livy update has also increased the maintenance cost of mercenaries from 125% of normal units to a staggering 200%. While they are still a valuable part of the toolbox, you have to be much more careful with deciding when and where to deploy them.

Imperator Rome Map

Naval Warfare

Navies in Imperator operate in a very similar manner to armies. Much like your land forces, you have to consider traditions, compositions, and tactics. There are six kinds of ships, two of which, the Octere and Mega-Polyreme, are locked behind certain military tradition trees. Ships vary in stats, but generally they break down so that the weaker ships (Trireme, Liburnian) are faster and cheaper to maintain, while the stronger ships (Tetrere, Hexere, Octere, Mega-Polyreme) are increasingly slower and more expensive to maintain, but do increasingly more damage.

It's important to note that Naval combat gives a bonus for the defender, incentivizing you to try and lure your opponent into a fight with you, rather than chasing down their fleet to engage. Like in land combat, units in the line will attempt to find a target to attack based on their positioning, which changes daily. Additionally, the basic stats for your ships can be augmented with both traditions and technology, so make sure you are investing in these areas if you're going to be focusing on the sea.

When engaging in naval combat don’t forget to select a naval tactic based on your current composition. Naval tactics work in a similar rock-paper-scissors format to the army tactics, so if you understand how to wage war on land, you can apply those same concepts to the sea. Choosing the right tactic is both about knowing your current fleet composition and predicting what you believe your enemy to be using.

The End, and a Beginning

While Imperator: Rome will doubtless be built up with numerous patches and DLC, the base game rests on some really interesting tactical foundations. Paradox has been very proactive at fixing what was lacking at launch in its two most recent updates, such as naval combat and a lack of any kind of food/logistical mechanic for your armies. Coming from a studio that often ignores tactics altogether or abstracts them away, this is a really positive step forward, and hopefully is a sign of things to come. Even if you’re not someone with a penchant for optimizing army compositions or micromanaging field armies, there is a lot of fun to be had in learning to manage the nuances of Imperator’s more combat-oriented gameplay.


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