Warfare is one of the three main methods of expanding national territory, the other two being diplo-annexation and colonization. Among the three, warfare offers the quickest means of expansion, but it lowers diplomatic relations with other nations and increases reputation.
Each army is organized into regiments of three different classes: infantry, cavalry, and artillery. An army has a minimum of 1 regiment, and may have an unlimited maximum; though the supply limit of a province provides a practical maximum number of troops. Each type of unit has 3 numerical values used to calculate its performance in battles:
- Fire - Applies to the "fire" phases of the battle
- Shock - Applies to the "shock" phases of the battle
- Speed - Determines the base speed of the unit when moving between provinces. An army only moves as fast as its slowest unit.
Each unit has an offensive and defensive value for each. In addition to regiments, each army may have a leader, which have their own values for fire, shock, speed, and siege, which applies to the army's ability to capture a fortified province. The leader's values are added to the regimental values in calculating battle success. There are dozens of different regimental types for each class, depending on tech group, technology levels, and other factors. Generally speaking, however, infantry units have better fire numbers, cavalry units have better shock numbers, and artillery units are needed to besiege a province.
Armies should be built of a diversity of troops, considering their purpose. By far, the most important troops in any army are the infantry. They do the bulk of the damage to other armies, and are required to assault a fortified province. Cavalry are useful in the "shock" phases of a battle, and can profoundly impact the morale of the opposing troops; however they are useless in sieges. Artillery, on the other hand, are vital in a siege, but move so slowly that they are not effective in all situations. When considering a holistic battle plan, you will probably want several different types of armies:
- Siege forces consisting of infantry and artillery (defensive cavalry are optional if you expect to have to defend against cavalry-based attacks)
- Battle forces consisting of infantry and cavalry used to bust the sieges of the enemy and chase their forces around the map (artillery are NOT recommended in these armies since they only slow you down.)
- Reinforcement forces consisting of infantry only used to provide assault forces to besieged territories and provide for the final assault on a fort.
As of DW patch 5.2, artillery no longer has a slower strategic speed, making it more practical to bring it with your battle armies; but you'll still have fiddly work to do concentrating artillery against forts once sieges are established.
Introduction to Land Warfare
There are three types of land units. Infantry, the one you will be using most of time. Cavalry that costs more than infantry and has more shock damage which helps routing enemy armies. Finally, after a few years of Land Tech research, artillery that costs the most but is more than very helpful during sieges and is a great asset in any battle you fight.
At the beginning, with low Land Tech levels, your cavalry will be superior. Basic infantry stands no chance 1:1 with a cavalry unit, especially if it's led by a great general. So for your early wars (Castille - Granada, Aragon - Navarra, Burgundy - Lorraine, Poland - Teutonic Order, Sweden - Denmark and the likes) it is advisable to use armies with many cavalry units; however, you lose the "combined arms" bonus if you have too much cavalry in your army (a proportion that varies with tech group).
So the basic early fighting strategy is to build one or two big armies with as much cavalry as lets you keep the bonus and assign generals to them (depending on your budget and manpower of course, as well as on the size of your enemy). For smaller countries like HRE minors (little countries on the area of nowadays Germany) you don't have to overstretch yourself like you would if you are fighting with France or Lithuania.
Now you have to find main forces of your enemy and order your armies to attack them. Make sure you have at least the same number or bigger and if you can spare cash, assign a general. Your army will fight and probably beat your enemy, making him run away in a random direction. Many new players think that the war is won already, we're not that naive. You have to order your army to march the way your enemy escapes (it is shown when and where he will arrive when you hover your mouse cursor over his army) and beat him again. You don't stop chasing them till the war ends or till they are all dead.
- Tips: To completely eliminate your enemy's troop, yours need to be at least double your enemy's size.
Now the second stage of your invasion. When their armies are beaten you can besiege their forts. For this you need a number of small infantry armies, with 1000 men per level of the fort to be besieged. March your unit into a province. When they get there they will start a siege. It takes a year or two for enemy to surrender. A good general and artillery units can shorten this time significantly. Do not assault a city unless you have at least 10 times more troops than your enemy. Otherwise you will fail and, in most cases, lose all your troops in the process. If you are really impatient, you can order an assault after the walls are breached, but remember that losses will be heavy and, worse, if your assault fails the enemy will hold the fort longer than he would have if you hadn't attacked.
After having won a siege your army will place a garrison inside so the enemy will have to siege the city if he wants it back. Thanks to that you can move your army further into enemy territory.
Baiting your opponent's army
This strategy works well against a fairly evenly matched opponent. Put your infantry on the front lines, but keep your cavalry one province behind. When you see the opponent's armies advancing on your infantry, check the arrival date by hovering the mouse over the opposing armies. Since your cavalry are fast moving, they should be able to reinforce your infantry in time. Try to time the cavalry's arrival to the same day as your opponent's arrival. That way, your opponent won't be able to back away before the battle begins. This tactic is eliminated in the expansion "Heir to the Throne" as cavalry move the same speed as infantry, and ping ponging is no longer written into the AI; but armies with high-maneuver generals can still be used effectively to reinforce armies under attack.
Fighting Using Attrition
Often it is best to fight on your own soil, rather than the enemy's, and to retreat from border provinces initially in order to invite sieges there which can then be crushed. Supply limits are greatly in your favour, and it's worth remembering that while completed sieges are the key to war score, incomplete sieges count for nothing, but an opponent who is out of manpower is completely at your mercy; hence destroying the enemy's armies may be a more important operational goal than initial siege success. Additionally, you have better visibility in such a conflict; rather than moving forward and hoping not to meet a large enemy stack coming the other way, you always have some warning as enemy forces move through the border provinces.
If you charge into enemy territory, their armies will concentrate to fight yours, and supply will be against you; if you let the AI into your territory, they will typically sit down for the first siege they come to, and you can concentrate forces against them - if they assault immediately, at least they have chewed up men and morale. Better yet, the AI may divide its forces into multiple sieges; these are reluctant to abandon sieges to support each other, so can be defeated in detail. Against a superior opponent, this may be your best hope of victory if they cannot swamp your entire empire.
If successful, the repeated victories will drive up your military tradition and give you a good war score. A very large opponent such as Ming will appear initially to simply replace every casualty by recruiting or replenishment, but as long as the casualty ratio is sufficiently in your favour, they will run dry before you. It can be a difficult decision in such a campaign as to whether to follow up a retreating enemy army; it could be annihilated cheaply, but your own army might get trapped by further enemy reinforcements.
Obviously, if you have overwhelming military superiority, there is no need to use this tactic. Additionally, if you have local superiority, a quick push into enemy territory can result in the annihilation of several regiments being recruited, a very nearly free source of war score and drain on their manpower. Using a spy to "Infiltrate Administration" will help in this case; you can also then use small siege stacks because you will be able to see the enemy building up a large force to counterattack and send your one large army to kill it. It is also useless if you need a quick victory (e.g. to release troops for use on another front), where the best hope will be to build up a decent war score quickly, perhaps by assaults, and sue for peace.
Newbies should note that armies can be hurt just as badly by attrition, as they can by combat. Fighting on your own soil can bring great harm to an enemy by attrition alone; the same is true when the situation is reversed.
Sometimes you will find that you get 1% attrition in a province, when your army is actually right at its displayed supply limit. This is because the province window's Supply Limit display rounds up from n.5, but the attrition code rounds down (it drops the .5). Because Owned provinces have a modifier of 5 times the base supply limit, an easy rule of thumb is that if the base supply limit has an odd-numbered decimal (e.g., 1.3 x 5 = 6.5, but it will display "7"), you will have the 1% problem. If you don't Own the province, just multiply the decimal by the corresponding status modifier, and only look at the resulting decimal. That's all that matters.
In some tropical lands (e.g., sub-saharan Africa), indigent nations do not get the tropical modifier - but you do. The effective supply limit for such provinces will drop when you take them, versus when you MA'd or Controlled them! Needless to say, you can suffer horrific attrition losses when fighting in such provinces, if they're still enemy owned. But then, their armies are usually easy to kill, and you get Controlled status (without the tropical penalty - they're still the owner) instantly when you defeat them, if they don't have forts.
Natives only subtract from an unowned province's Supply Limit when they are fighting. Try to avoid fighting them at the end of the month.
In Europa Universalis most values are updated on a monthly base. Therefore it is always crucial where your armies are on the last day of the month. Concerning this there are two important facts that can be exploited for effective warfare:
- A moving army is for unit support limit purposes located in the province from which it comes until the day it arrives at the neighbouring province. This means, if an army arrives on the first of may it is restocked on the last day of April as if it was not moving.
- During a fight, army supply limits are without effect. That means that during a fight even 100 units in a province that can only sustain 10 will not suffer any attrition.
After a fight (if you flee or won) with much more troops than the province can sustain, try your best to leave the province in such a manner that you have already left the province at the months end to circumvent attrition. So if you flee some troops from the battle, do it on the first of a month. In most cases they will arrive in the next province before the month ends and not suffer the terrible attrition. This is even more important, when the earth in the province is scorched.
If you are attacked in a province and want to buy time, scorch the earth shortly before the enemy troops arrive but either do it in the beginning of a month, so you can still flee before the enemy arrives and before attrition strikes, or do it in the month the enemy arrives, fight him until the first of the next month and then flee. If you have forts of level 2 or higher you can sometimes watch enemies as they melt away one huge stack after another, repeatedly breaking up the siege as soon as they feel beaten too hard by attrition. If you then do well-timed hit and run strikes with cavalry (In Nomine: arrive 4 days before months end, so the battle ends earliest on the first of the next month) you can win wars against ridiculously superior armies using scorched earth in combination with high level forts.
Another less important point is: If one of your troops needs to heal or recover morale once more before it can enter battle again, just send it to arrive on the first of the next month, this way it wil be able to recover. If you pursue an enemy army with cavalry and a fight in enemy territory ends near the end of the month check how many days before the enemy you can arrive in the province he flees to. If you have the time, do not pursue him until the first of next month because unit limit in enemy land is doubled during sieges, so you can heal better while your army is not moving (so it will automatically siege). Send them to overtake the enemy on the first of the next month.
Evading a Truce
If you have a truce with a nation but would like to return to war with them before the truce expires, declare war on one of their allies or on a nation they are guaranteeing. They will almost always declare war automatically, and therefore disregard the truce.
Inferior Tech Groups
The different tech groups have different unit types as detailed in the articles Infantry and Cavalry (artillery and ships are the same for all). In the vanilla game, westernization will allow you to build units of the new tech group, while in IN you are stuck with the units of your starting tech group. Comparing the units you will find that the Latin tech units are by far superior with few exceptions, like the eastern tech and Chinese tech cavalry being comparable until land tech 36 (and for the Chinese even beyond).
There is a possibility to build units from different tech groups: if you take provinces in a peace agreement, you can build the units of your enemy there until you get cores on these provinces (this means for 50 years in IN). Thus to keep up with Latin tech armies, it suffices to take some provinces from a Latin tech country every once in a while and build their units there. For example, a Muslim nation should head for Latin tech minors (e.g. in Italy) to be able to face the armies of the other European countries like France. However, these units won't be upgraded when you change your preferred unit type, so taking this approach means a lot of additional expense if you want to keep them up to date (that said, even an out of date Latin unit may be better than your most recent unit in your own tech group).
With every land battle you win you get additional Land Tradition. The bigger the battle and the more casualties you inflict, the more Land Tradition you gain. High Land Tradition helps you recruit better generals and those you employ while "you have high land tradition" flag is up (90% and more) are real gods of war and their names are feared all over the world. You know such guys from history, Frederick the Great, Napoleon, Attila, Genghis Khan, Marlborough...
Strong generals are essential on higher difficulty settings.
However, good generals can be recruited already at 25-30%, and those (and slightly better) are the ones that will be most common throughout the first 200–250 years of the game. It might be a good idea to save up your Land Tradition to at least 25-30% before recruiting a general, considering both the cost in ducats and the small decrease your Tradition suffers upon recruiting. Recruiting a general also consumes a diplomat (i.e. you train/promote him into a general).
Considered by many to be an emergency option, but very frequently used by most players and always by the AI, is the option of converting your (male) ruler into a general. His stats are determined primarily from his military attribute (meaning a 6 would be pretty good, a 9 a god, but a 3 not necessarily a complete loser) but also slightly from your Land Tradition. This option is free and doesn't use any diplomats; however, it endangers your ruler's life. To get your ruler killed in combat, or siege, decreases your stability by 1, and of course risks the potentially nasty effects of a Personal Union, a Regency Council or a Succession War. But maybe the ruler wasn't that much to put in the shelf anyhow, and his successor is the Peter the Great you've been waiting for?
There is also one special general, the Conquistador. He is the only person skilled and brave enough to be able to lead his troops into uncharted Terra Incognita, but may only be recruited by a government following the National Idea of Quest for the New World.
Very much like generals, but traveling the seas instead, the admirals are a very important factor to be able to get the upper hand, this time on water. Admirals are recruited exactly like generals, costs an amount of money, 1 diplomat and a bit of Naval Tradition. Naval Tradition is acquired from fighting Naval battles and causing/receiving casualties. The more Tradition you have, the better admirals you will have; at around 50% you'll get very able admirals with the ability to completely turn the tide in the Naval struggle. A ruler can never be converted into an admiral.
There is also one special admiral; namely the Explorer. This skilled person is good at, you guessed it, exploring, meaning he is the only admiral able to sail into, and reveal, Terra Incognita sea zones. You will have to have the National Idea "Quest for the New World" to be able to recruit an explorer. Exploring new sea zones will increase your Naval Tradition.
Whether your army is successful on the battlefield or not doesn't depend only on your soldiers and generals. If you want to fight a lot it is important to set your Sliders and national ideas accordingly.
Cost and time it takes to recruit a unit depends on its price. The price changes when you move your Aristocracy/Plutocracy, Land/Naval and Serfdom/Free subjects sliders. The more aristocracy, land and serfdom orientation you have, the cheaper your units are and the quicker they build. Free subjects makes your armies morale grow.
Another important setting is your Offensive/Defensive slider. If you are all defensive it is easier to you to recruit artillery and to siege cities. But I advise to go all offensive, this makes your armies deadly and your leaders to be feared.
The last domestic policy you probably want to adjust is Quality/Quantity. If you have a huge country with a lot of manpower you can afford to reduce it a bit by selecting Quality, but a small country may need Quantity to get enough manpower to be able to replenish armies at all. I advise staying close to the middle here, and to Quality or Quantity depending on your personal preference.
It is easier to understand all of that comparing different countries. Start a game with Portugal and Burgundy for example and compare their sliders. Portugal is the best country to build a colonial and naval power. Ships build fast, have great morale, cost nothing in comparison with other countries. Burgundy is a predator, a country for warmongers. It is set 100% to offensive, its armies are strong and its leaders are more than capable. Portuguese army is no match for Burgundian one. But if you try to build a ship in Burgundy, you will see it costs you a lot more and builds a few times longer. If you try to colonise anything with Burgundy, you will notice how hard it is to get new colonists. This is the price they pay for their elite armies.
The first national idea for everybody who wants to fight early wars is Military Drill. It gives you a nice bonus of 0.50 to your armies morale. It makes them stand and fight in situations when others would run. And the longer they fight the bigger your chances for enemy to rout are.
If you are a small country and have difficulties in recruiting any army, you can go for National Conscripts (+50% manpower). It is useless for big players like England or France.
Grand army rises your limit of armies before penalty triggers on, Engineer Corps helps in sieges but the bonus in not significant enough to consider it useful, Battlefield Commissions rise your land tradition slowly which helps you in a war after a long period of peace to recruit good generals. Glorious Arms is the idea that allows you to make tons of prestige from land battles, so even after beating a small country you will have a significant prestige percentage and thus your diplomatic efforts will be more successful that they used to be. Military Drill works for most of the countries, National Conscripts is useful for really small ones.
There are four types of ships in the game. Big ships, Light ships, Galleys and Transports. Only ships from transport category can carry your troops. Others differ in their speed, number of cannons and hull strength. The more here means the better and each battle is about numbers, hull strength and admiral skills.
Fleets can blockade ports reducing amount of overseas income that the targeted nation earns. You need Naval Tech level 9 (tech level 2 in EU3 & NA) for that. They can also blockade straits forbidding enemy armies to cross them. If you want to get advantage from that, for example holding Danish army on their capital island while you take over their other provinces you have to realize that your blockade doesn't work while your fleet is engaged in battle. That's why it's important to guard not only the strait but also sea sectors adjacent to it. This way your enemy won't be able to move his troops through the blockade after engaging your blocking fleet. Just make sure that others fleets are strong enough to keep him away from your main blockading fleet.
If you position a fleet in a sea province that borders an enemy port, it will initiate a blockade. You will see a graphic appear on the map, showing a net that encircles the port. Coastal provinces are assumed to rely heavily on maritime traffic for their income, so a blockaded province will generate only 25% of its normal tax and trade revenues until the blockade can be lifted.
If the country that owns the port receives any income from overseas colonies or centers of trade, and the port belongs to province that is directly linked to the country’s capital, a percentage of this overseas income will be captured by your fleet and be diverted to your own treasury. If you are able to blockade all of the enemy’s home ports, you can completely cut off his overseas income while making a very tidy profit yourself.
In NA and EU3, you don't have to build large fleets if you have a large colonial empire. You can take over pirate ships that appear next to your lands instead. Just send your fleet to where pirates are sighted (you must have seen such messages) and beat them. After each battle there is a chance that the pirate ship will fall into your hands. A good leader (explorer or admiral recruited during "you have high naval tradition" flag) and strong navy can help here. This way it's possible to get around 10 free Carracks a year in the British Caribbean. If you lack large colonial empire, you can always wage a war with a country who has strong navy and hope to take some of their ships during your battles. Just make sure you win, if you fail they have chances to get your ships.
In IN you can no longer capture pirate ships, and a large navy is required to collect tariffs from your colonial provinces.
Additions in Heir to the Throne
The latest additions to Heir to the Throne have, to say the least, rewritten the rules of warfare in EU3. The first order of business pertains to the fact that cavalry and infantry now march at the same rate, rendering cavalry chasing down armies almost useless. However, morale now plays a much larger role in battle, the mechanics have been changed to stop the constant ping ponging resulting from an armies defeat. This presents a double edged sword, make sure that upkeep is kept full in war, and make sure to chase an enemy down to the last man if you have the ability to do so.