Hearts of Iron 4 (HOI4) – What Is Combat Width?

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All Paradox Interactive games have some type of Combat Width mechanic in them to make sure that the country with bigger armies won’t win just because they stack all their troops on top of one another.

The problem with Combat Width is that it’s never explained properly, and you will likely just occasionally see it come up in battles or while editing divisions.

Recommended Read: Best Tank Designs in Hearts of Iron 4

Unfortunately, it is a relatively important thing to understand since you can get a maximum debuff of 30% to your Attack and Defense stats while fighting.

Combat Width is a stat in HOI4 that decides how many divisions can take part in a battle at the same type, which is decided by terrain. If the Combat Width is exceeded, the player can get debuffs to their Attack and Defense throughout the battle.

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What Is Combat Width in HOI4?

Combat Width in HOI4 is the amount of space that divisions can take up in a province battle.

Each province will have a set maximum Combat Width based on the terrain type (Plains, Urban, etc.), and each division will have its own Combat Width stat, which will decide how they fit in the battle.

When you create a division using the division designer, you will notice that most line battalions will add either 1, 2, or 3 Combat Width to your division, with most of them using 2 (Support Companies don’t add any Combat Width).

You can also check the Combat Width of a province before attacking by clicking on the tile and hovering over the image of the Province in the bottom left corner of the screen, which will tell you the terrain type and Combat Width.

When you start a battle, you can see if you open the fight menu (press the bubble with numbers in it) a number in the center that represents the Combat Width.

This can also change based on how many directions the province is attacked from (+half of the normal Combat Width per attack direction).

How Combat Width Works Example

So, here is exactly how Combat Width works in action in HOI4: If a battle has 90 Combat Width, then the game will allow at least 90 Combat Width worth of divisions in the battle.

If you have 4 30 Width divisions, then 3 of them will enter the battle, and the 4th one will be out of the battle, in reserves, waiting for a space to enter the fight.

However, if you have 4 29 Width divisions, then all 4 of them will take part in the battle, exceeding the Combat Width by 26.

This is because once three divisions have joined the battle and their Combat Width isn’t larger or equal to 90, new divisions will join.

The problem with this is that the divisions will get debuffs to their Soft Attack, Hard Attack, and Defense based on how much you passed the Combat Width.

Due to how this mechanic works, players will often exceed the Combat Width since you can easily get over it just by making divisions that don’t have Combat Width ending in 0 or 5.

Exceeding Combat Width Debuff

Here is the exact equation used to calculate the Exceeding Combat Width debuff in HOI4:

(Total Width – Battle Width) / Battle Width * 100

Total Width stands for the number of Combat Width your divisions get for the battle. Battle Width stands for the Combat Width of the province. You can see both just by opening a battle by clicking the battle bubble on the map.

Let’s say you are fighting in a province with 105 Combat Width (Battle Width) where you have 118 Combat Width on your side (Total Width).

This means that you will get a -12.3% ((118-105)/105*100) Exceeding Combat Width debuff to your Attack and Defense for all the divisions present in the battle.

The maximum Exceeding Combat Width debuff you can get is -33% to Attack and Defense, but the normal amount you will usually get is between 10 to 20% if you don’t use optimized Combat Width for your divisions.

Combat Width for Terrain Types

All terrain types in HOI4 have different Combat Widths:

  • Urban – 80 Combat Width
  • Desert – 70 Combat Width
  • Plains – 70 Combat Width
  • Hills – 70 Combat Width
  • Jungle – 60 Combat Width
  • Forest – 60 Combat Width
  • Mountain – 50 Combat Width
  • Marsh – 50 Combat Width

All of these can also get extra battle width if you attack from different directions which will give you an extra half Combat Width per direction of attack.

What Is the Best Combat Width?

When optimizing and designing your divisions in HOI4, you need to make sure that you choose the best Combat Width that will get the least amount of negative modifiers in most terrain types.

One problem that you can often bump into is making your divisions too small (less than 12 Combat Width) or too large (bigger than 40 Width), which will often either give you horrible Combat Width debuffs or just bad stats in the battle.

Taking this into consideration, the best Combat Width stats that you can use for your divisions in HOI4 are these:

  • 14/15
  • 18
  • 24/25
  • 35/36

If you were to do some math, you would see that in most terrain types, these Combat Width stats will usually get you the least amount of negative modifiers.

The best ones actually are 14, 15, and 18, with 15 as the best overall Combat Width in all terrain types in HOI4.

Also, 24, 25, 35, and 36 are the best Combat Widths to use if you want to field relatively large divisions.

That’s everything you need to know about Combat Width in Hearts of Iron 4!

Have any input or suggestions for this guide? Let us know in the comment section below.

Adrian Oprea

Based in London, United Kingdom, Adrian Oprea is a Guides Writer. As a professional single-player RPG player, Adrian has often been stigmatized. He has decided to pour his frustration into writing guides!

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