How to do Attritional Warfare
Attritional warfare is a method of inflicting loss on an enemy, by using attrition instead of battle. As a tactical maneuver, it can help you beat particular enemy stacks by wearing them down. Attritional strategy is also a possibility in EU2, although relatively rarely outside of special situations.
Where Attrition Can Work
Attrition can work for you in any land province where you get more supply than an enemy does. To make it work well, you need significantly more supply.
Here are the set of cases where you are likely to have a large supply advantage:
- in winter, in any owned province.
- in owned provinces with relatively high base tax value. If the BTV is low, then you can still get a supply advantage, but it is small.
- in owned provinces that are fortified.
- in fortified provinces owned by a member of your war coalition.
- in high base tax value enemy provinces where you have military access and a blockade. This is a minor twist to the ahistorical exploit of Military access with enemies.
There are several kinds of situations where you might use attritional tactics. Sometimes you are sure you won't win a battle, i.e., against a dogpile sieging in mountains. Or you might be able to prevail, but at a high cost in lost men, and there is no time pressure. In those sorts of situations, you don't even try to fight the battle. However, often you want to at least probe the enemy in combat. The idea is to let combat go for long enough to see if there's a chance of winning.
Waiting to Attack
Sometimes the enemy will decide to siege a province that happens to be low in supply, and he will take lots of attrition there, without you having to lift a finger. In cases like this, you can attrit the enemy without doing anything yourself. So, it's often best to simply let the enemy siege for a while.
You may want to break the siege when it gets near to complete. (You can watch the siege progress bar to give you an indication of how far the enemy is progressing.) Or, you might just let the enemy complete the siege. Usually in that case, the survivors will march back into their own territory, and you can move in behind and start your own siege to retake the city.
Winter is a sort of special case here: in winter, every province you own has no supply for the enemy.
In general, you'll want to carefully examine the supply levels, to make sure that you do not take attrition yourself, from lack of supply. Also, you want to use the minimum force possible to attrit the enemy, because your force will be moving at the end of the month, and thus it must take 1% movement attrition. 1% isn't very much, but it's not free, either, especially with a large force.
How do you know what size of army to use? Here's how. First, you should calculate the maximum force you can supply in the province: call that number F army units. Next you should account for the existing enemy force, as well as any other forces that you expect to be in province at month's end (either friendly AIs or the enemy); call their total E army units. Thus, F-E is the amount of "spare" supply in the province, for you. As a first approximation to your ideal attritional force, you want to move in F-E armies.
There are two situations where F-E is not exactly what you want. First, you need to understand the rules for maximum attrition. If the enemy force can be made to suffer maximum attrition, you only need to move in enough men to cause that, and no more. (In fact if the enemy is already at maximum, you don't need to move in at all! This is one example of the case "waiting to attack", above.)
Second, for a sufficiently large enemy force, because enemy forces take attrition first, you can actually move in just a bit more than F-E army units, counting on the attrition inflicted to reduce the enemy's effective size enough to allow you to safely support a few more unattrited.
Once you have decided on the force size to use, you must give it orders to move to the province, then when battle starts, immediately voluntarily retreat. You want to make sure that the retreat will still be going on at the last day of the month, so you need to understand land movement times.
The downside of simple attrition is that it costs you warscore for losing the battles. And you also take movement attrition, so it is not free. However, if you can routinely attrit an enemy by 20% per month, while you suffer only 1% yourself, pretty soon you will be able to safely engage him in battle.
Oftentimes you encounter a situation where you can engage an enemy and attrit him, but you have some hope of winning the battle, and would prefer that. But you'd prefer even more not to take risks with your costly men. In this situation, you want to do what I call an attritional probe.
The idea here is to synchronize a single day of battle with the infliction of attrition -- so, the day of battle is the 1st of the month. To do this, you must master land movement times, so that you time your force's arrival exactly for the 30th of a month (the 28th in February).
When you arrive and battle starts, you get a message. Pause. Check out the attrition levels displayed, to make sure that you calculated them correctly. Now carefully unpause and repause, to run the game for exactly one day, no more. Now examine the morale damage you've taken (which is easiest to see), as well as your own casualties. And also look at the enemy's morale and his damage, although his damage will include the attrition just inflicted. If you got a particularly favorable result, then you should let the battle go for at least the phase (the next 4 days), to see if you can win it. Otherwise, it's the first of the month, so you can retreat without even taking movement attrition!
Attrition Against High Tech Enemies
If you are a low-tech country facing a higher-tech foe, then you'll want a slight variation of the attritional probe, which is the combination of an attritional probe with a "fire phase soakoff". (See XXX.) In this tactic, you send your soak-off force, usually just a few thousand men, exactly timed to arrive on the 25th of the month. Then you send your main force (usually a huge army that is mostly or all cavalry), timed to arrive on the 30th.
If you are not lucky, the soakoff unit will have their morale broken in the first fire phase, before the main force arrives. In this case, you either cancel the move of the main force and try again in a month, or you let it arrive but then immediately retreat it (i.e., just use it for simple attrition).
Ideally, the soakoff unit manages to make it through the first fire phase. Then, just in time for the first shock phase, your main force arrives. This boosts your total morale to almost full, so your units can still fight. Since it's the last day of the month, you get to attrit the enemy, at the least. And you also get in one day of shock phase, to see how much damage you might get if you stand.
You can often annihilate small enemy forces using this tactic. If you get a poor shock result, at least you attrit them, and can keep trying without very much damage in men or morale.
By "strategy", I mean here a means to win a whole war. Attrition can be used strategically only when the following conditions hold:
- warscore losses from lost battles can be overcome
- you can prevent the enemy from building as fast as you can attrit him
These conditions present problems, especially the latter one.
Warscore losses from battles can be overcome in two ways. One is just going for 100% warscore, which you should be doing in most wars anyway. The other is by stomping lots of armies as they are recruited, when they are small and low morale. One tactic you might use, particularly if you cannot reach the enemy homeland easily or at all, is to allow him to build on provinces that can you can reach, where you know you can easily beat him in battle.
If you know you will eventually get 100% warscore (i.e., you plan to control every province owned by the enemy war leader), then you don't have to worry about warscore losses on the way. On the lower AI levels, you can outbuild an AI! Of course, usually if you can outbuild them, you can also just beat them flat-out in battle. But not always.
Generally speaking, you cannot win wars via attrition at the higher difficulty levels. The problem is that AIs are given cheats that make it impossible to stop them from getting income, or recruiting, such that you can never outbuild them without covering all their lands. However, there are a few exceptions to those observations.
First, in "wars" vs rebels, the enemy is only a particular stack of rebels. It cannot recruit, and so it is the ideal target for attrition. It can be very helpful to attrit a large stack of rebels down to a manageable size before attempting to destroy it in battle. See the article on How to Handle Rebels for more discussion.
On the higher difficulty levels, to win most wars you must cover all provinces the enemy can recruit armies on. Once you've done that, then you can often use attrition as your main method to destroy large enemy stacks.