[HOI4] An In-Depth Guide to Land Combat

hello hearts of iron players my name's Raymond and today I want to talk about how combat works and hearts of iron for this will be a guide that explains how units do damage to one another and how the different combat stats are related to each other as with all of my guides my aim is to be efficient and thorough I'll use plenty of examples and show how the combat equations function to give you the details of casualties and losses then towards the end of this video I'll present some rules of thumb that demonstrate important implications of the battle system for template design army composition and overall strategic planning to start out with there are two important numbers relating to a divisions health that you can see on the unit panel there's a green bar and a brown bar the green bar represents organization when the unit is engaged in battle this functions very much like the morale bar in eu4 and that it's essentially engaged to see how long the unit can stay in the fight before being forced to retreat when it hits zero the unit is either forced to stop the attack if they are on offense or move back to another province if it's on defense also like morale it has no bearing on combat effectiveness a division at one percent of its organization will fight just as well as a unit with 100 percent of its organization it'll just be closer to retreating organization is the primary determinant of which side will win the battle when you see the little battle indicator the number shows you the balance of organization and the color represents which side is projected to run out first with green meaning victory is likely for your side divisions not fighting will begin to recover organization quite quickly finally a unit with low organization that moves slower when it's making hostile moves into enemy territory the penalty starts at 50% of Units organization and scales downwards linearly so that a unit loses 80% of its speed at zero organization the other bar you can see on the unit panel is the brown bar indicating fighting strength which measures what percent of the necessary man and equipment the division has depletion of this bar does impact combat effectiveness and so a division with 50% strength would lose half its attack and defense values this bar also has to be reinforced from your equipment storage and manpower pool although it typically gets reduced at a far slower pace than organization as we'll see later okay so let's show an actual battle to keep things as simple as possible I'm going to be using a division with three infantry battalions on both sides I've also modified the game to stop ephemeral bonuses and penalties from changing things things like entrenchment commander's weather terrain day time etc have all been removed so things stay constant so as the battle begins you can see the battle screen appear for this first example we'll be interested in three stats soft attack defense and breakthrough we can completely ignore heart attack for now since both divisions are comprised of infantry which are entirely soft the soft attack represents how many dice the division rules every hour to see if it can do damage to the other side for example the attacking side rules 18 dice every hour to try to hit the defenders then the defenders have a stat known as defense that helps block some of the damage every one point of defense plots one attack if the attack is blocked by defense it has only a 10% chance of hitting if an attack isn't blocked it has a 40% chance of hitting as you can see the defending infantry have a very high defense that's bigger than the soft attack of the offense so all of the offenses attacks will be blocked so they all only have a 10% chance of hitting on average we would expect 1.8 of the offenses attacks to hit every hour or 43.2 hits every day the defending side also uses its soft attack to strike back in the same way the only difference is the attacking side users break through to block attacks so defense is your defense while defending will break through is your defense wall attacking you can see that breakthrough is quite low and many of the defending side shots won't be blocked hence we expect the defending side to hit 4.5 shots per hour or 108 shots per day when a division is hit it takes damage to both its organization and its fighting strength it takes the number of hits multiplied by the damage fire in the game files which is always point oh five multiplied by a dice roll divided by ten the last number the division by ten is a number I approximated from statistical inference some people have done experiments in the past and they approximated the division to be by twelve but when I did the experiments myself I found it closer to ten so either it changed or we somehow got different data sets regardless the number doesn't appear in any of the game files anywhere and ten is always close enough so we'll use it for our purposes the other interesting number is the dice roll which rolls between a 1 2 3 or 4 for damage to organization and rolls between a 1 or a 2 for damage to strength so each hit will deal between 0.005 2.0 2.oh damage to organization and between 0.005 2.0 100 damage to strength the damage to organization is straightforward it just gets applied to the base value so a division with 60 organization that takes 20 organization damage we'll have 40 organization damage to strength though has to jump through one more hoop and that damage is applied to a stat called HP if a 25 HP unit gets hit 400 times it will take an average of 3 HP worth of damage this means that we'll have 88% of its HP left which means it will have 88% of its strength left in other words it will have lost 12 percent of its manpower and 12 percent of its equipment so if we let combat play out we can see the defending side wins pretty handily and it's all because the attacking side has low break through the unit that runs out of organization will be forced to retreat when combat ends any damage done to strength is immediately refunded by 30% to represent missing soldiers returning to their divisions and that's pretty much it that's a basic overview of combat the game has a huge amount of modifiers like entrenchment unit veteran C planning bonuses weather and on and on and on but they don't change anything fundamental they just push numbers in the system up and down for this next example I want to explain that heart attack which we ignored earlier this time I'm swapping out the three infantry battalions on the attacking side for motorized this gives them 20% hardness as you can see in the division design window what the hardness versus softness percent tells you is what percent of the hard and soft attacks the enemy will use against you with regular infantry division's softness was 100 percent so 100 percent of the soft attacks were used while 0 percent of the heart attacks reused now with 20 percent hardness and 80 percent softness the amount of attacks made on the division that will be 20% of the heart attack value plus 80 percent of the soft attack value when the battle starts the trucks on the offense will still do the same amount of damage since their attack values haven't changed however the amount of attacks they receive from their enemies will change from 18 to 15 based on the math shown here and since they still have 9 break through 9 of those attacks will be blocked while 6 won't be so we expect them to be hit 3.3 times per hour or seventy nine point two times a day hence they'll be taking quite a bit less damage than the pure soft Infantry Division that preceded them you can see they fight a lot longer before retreating in the next example I want to explain armor and piercing if a division fights another division it compares its armor value to the enemy's piercing value if the enemy's piercing value is higher nothing changes if the enemy's piercing value is lower though it gets some bonuses here I've changed the trucks into three light armored battalions which have an armor value of 10 then if I switch back over to Bulgaria you can see their infantry division 2 has a piercing of only 4 so when the tanks go to fight the infantry they get the bonus the main portion of this bonus is that all attacks do half damage to organization and strength and this bonus applies after things like break through that already reduced the hit chance I don't have to tell you that it's a pretty powerful bonus but it gets even better if a divisions armor isn't pierced it also gets an attack bonus as well the dice and the organization rules go from 1 to 6 instead of from 1 to 4 making the average rise to 3.5 from 2.5 in other words it does 40% more organization damage to represent its freedom of movement even though the tank division has a measly 10 organization and only 6 HP it will he'll end up winning because of this bonus and since it has a high breakthrough and 80% hardness even though the attacks on both sides are blocked by defense and breakthrough the tanks end up doing 21 times more organization damage which lets it deplete the 60 organization of the Infantry Division much faster than the infantry can deplete the 10 organization of the tanks in the next example I want to explain reinforcements in combat width first up is reinforcements most of the time battles won't be one division of fighting against one other division you'll have multiple divisions coming from several provinces when you declare an attack it starts the next hour assuming the enemy province is adjacent if you ordered a bunch of units to attack at the same time then they'll all join the fray at the same time with no problem this also applies to units attacking from another province as long as they all start the battle at the same time they all join immediately however if you have divisions during the battle later on perhaps as reinforcements or after they finish moving to another province they do not join the battle immediately instead they get put to the reserves and have to reinforce the base chance is 2% per hour so if we do a bit of math we can see the average time would be over 34 hours which is a really long time to not be shooting at the enemy with the radio tech the chance increases to 7% per hour which makes the average time become nine and a half hours finally through signal companies you get a stack called initiative which the game divides by four and adds to the reinforced rate so a top tech signal company gives 56% initiative which gets divided by four and added to the base rate of two in the radios tech of five for reinforced rate of twenty one percent per hour or an average time to reinforce of just under three hours next let's talk about combat width like most paradox games you can't just dump a hundred units on an area and have them all fight at the same time and high for unit divisions have a stat known as combat width which represents how much of the frontline they take up a battle where an attack is coming from one province will have a width of 80 and then for each additional province the attack is coming from the width will increase by 40 so if a province was being attacked from three sides the combat width would be 100s so 160 width of divisions from both sides could participate in the battle and all the rest would be reserves which could eventually participate if other frontline divisions lose all their organization in which case they'll have to go through the normal reinforcement process I mentioned earlier beyond these stats there are a few others to keep in mind every 24 hours of battle tactics will change I had modded them to have no value for ease of explanation but all they do is change values up and down so they're pretty straightforward if you have a recon company for higher reconnaissance you have a better chance of using a counter tactic for more bonuses then there's entrenchment which again just gives you bonuses to attack and defense and after all that the other stats really only apply out of combat and are fairly self-explanatory so that's combat and hearts of iron for here's what it looks like when I don't hold all those other modifiers constant there's a lot of ups and downs all over the place but again those are simply changes in modifiers to the base values mostly to defense breakthrough and soft and heart attack the actual mechanics of the battles will always be the same as I've described them here now I want to go over some of the implications of how the combat system is designed you've probably picked up on a few of these already but I want to make them explicit because they can have a big impact on your philosophy for division design so first off let's talk about the basic combat stats of Defense breakthrough and soft attack defense and break through are a bit unusual and that they can both be wasted if you have too much of them they can essentially overflow and provide no more benefit so if you think back to the original example of a division of three infantry battalions fighting a copy of itself you can see that the soft attack on both sides is 18 which means 18 attacks are made every hour the defending side has a defense value of 66 which blocks all the offenses attack attempts however it goes way above and beyond because all they need is a defense of 18 to block all the attempts and any defense beyond that functionally does nothing they get the same effect out of 66 defense as they would out of 18 defense or 10,000,000 defense since defense can only block a shot there's no benefit to having a defense value that exceeds the number of attacks likewise if you think back to the tanks fighting the infantry the breakthrough exceeded the attack of the defenders by quite a bit hence and an overarching sense each additional point of Defense or breakthrough is less important than the one that preceded it because it has an ever-increasing chance of being more than you'd ever need and thus overflowing and doing no good on the flip side you can take a look at soft and heart attack you will never waste attack because it can always be used it doesn't have to have some enemies stat that precedes it to make it function in fact it's better if the enemy doesn't have the defense to counter it because as I stated earlier an attack they do have the defense to counter has a ninety percent chance of missing while an attack they don't have the defense to counter has a 60 percent chance of missing in other words each point of attack that exceeds the enemy's defense or breakthrough is four times better than a point of attack that doesn't this leads to a very close corollary that each additional point of attack is better than the one that preceded it because it has an ever-increasing chance of exceeding the enemy's defense and doing quadruple damage now don't take what I'm saying in the wrong way by thinking you can get away with really low defense defense is incredibly important and if you skip on it you'll find all your divisions dead really quickly however you should try to make it as low as possible so that you can cover against all enemy at acts without wasting a bunch in a perfect world if the enemy made fifty attacks you would have exactly 50 defense but this is a paradox game so there are bajillion modifiers everywhere which will make any sort of precise optimization like that utterly impossible but if you look at your tank divisions in combat and consistently see them having five times more breakthrough than they actually need then you should think about swapping out some of your tanks for self-propelled artillery thereby moving away from the useless breakthrough towards more soft attack that will let you kill enemies more effectively likewise if you're strategically on the defense and you see that you're entrenched infantry have way more defense than they'd ever need to swat away the enemy you can think about changing out some of your infantry for artillery so your divisions can kill more effectively next since units that attack use breakthrough and units that defend use defense divisions that only Tapp will only care about breakthrough and can ignore defense completely likewise divisions that you only plan on having defend will only care about defense and can ignore breakthrough entirely this means you'll want to specialize your divisions to have some dedicated attackers and some dedicated defenders for example when you make an armored breakthrough you can have your tanks leading the charge to punch a hole in the enemy's line and have them keep pressing on until an encirclement is complete behind them you can bring in motorized to hold the line till you can mop up the pocket in this case it's important for your tanks to never stop attacking and for your motorized to never attack at all because this place to each of their strengths of high breakthrough and high defence respectively moreover when you're not planning on attacking for a while you'll probably want to move your tanks off the frontlines so they don't get pushed into defending additionally you really don't want to be attacking with general infantry a lot of times I see people putting all their infantry on the front drawing an arrow and letting the AI slowly push the enemy back that can be ok when you have massive superiority but if you only have a medium sized upper hand against your enemy then the AI will push your enemies back but at a serious cost and manpower since infantry have terrible breakthrough in short don't use low breakthrough units as general-purpose attackers use them as cost-effective ways to hold the line and sparingly use them to pin enemies mop up encirclements or make a tax of opportunity when they have massive superiority next let's talk about piercing an armor so armor on your tank divisions is a bit like defense and that it can be wasted if your enemies only have 50 piercing then you get the same amount of benefit out of 51 armor as you would out of 500000 armor however the thing with the armor bonus is that it's completely binary either you get the full effect or you get nothing with defense if the enemy makes a few more attacks than what you can block it's not too bad but with armor if they have 50 piercing there's a world of difference between you having 49 armor or 51 armor the armor bonus represents 40 percent of your offense and half of your protection it's what makes Tanks special so you need to have it I love having quick break through units but even though light tanks are quicker their little armor by means always prefer medium tanks because of their better protection armor is important enough that you shouldn't worry about wasting it sure your tank still have their hardness and high breakthrough but at the end of the day pretty much half of their combat potential is tied up in the armor bonus if your enemy is consistently piercing you you'll probably want to rethink your strategy next let's talk about reinforcements this is a minor tip but there are definitely places it could be useful if you'll remember all the divisions that start an attack on the province at the same time will immediately join the battle as long as there's enough combat with for them because of this if you need one of you units in the battle right now and you're the attacker what you can do is pause the game stop the battle and then restart the battle with the divisions you need to engage them immediately the only thing that will change when you do this is both sides will get the 30% refund to their strengths that normally occurs at the end of a battle the important value organization stays exactly the same this is great if you're just about to close of encirclement and you're coming up on the rear of the enemy front if you already have your infantry attacking then the battle will already be happening and it can take hours or even days for your tanks to join the fray which can represent thousands of attacks lost and precious time which enemies can use to escape use this little trick to save some critical time and close that encirclement with the utmost haste finally two notes on combat width the first is that the combat with is completely in the hands of the attacking side but it applies to both the attackers and the defenders if you're attacking into a province with a lot of enemies and you can't fill the combat width you're only doing yourself a disservice by attacking from multiple angles in general maximize the amount of combat width and battles up to what you can fill but don't give your enemy a free advantage by letting them bring more wit than you can and second you want divisions that are easy to work with in terms of combat width you want easy multiples so widths of 10 20 and 40 are best or if you have the general trait that decreases width you can go 11 22 and 44 these widths can form the baseline of your divisions so if you want an offensive tank division you'll know you want to with the 40 then you can work out how much breakthrough soft attack and HP you need to decide how many tanks self-propelled artillery and motorized you what to include if you have a weird combat with on all your divisions like 17 then you're just making a mess for yourself so that's been an overview of combat and hearts of iron for I hope a look into the fine details has given you some insight into how the mechanics work and what some of the major implications are my name is Raymond and until next time thanks for watching

Channel: Reman's Paradox

Views: 279,652

Rating: 4.9448743 out of 5

Keywords: Paradox Interactive, Hearts of Iron 4, HoI4, Land Combat, Combat Mechanics

Id: fbBjywJmcEM

Length: 20min 4sec (1204 seconds)

Published: Wed Dec 20 2017

Reddit Comments

[u/KhanOfMilan]

This is a very useful and detailed guide, and I highly recommend giving it a watch. I myself learned some new stuff with how valuable excess attack is, and how one should tone down excessive defense/breakthrough in favor of other stats.

Could someone fill me in though, if strength damage is equally split between manpower and equipment, is the reason I often see more equipment than manpower losses because of various forms of attrition and field hospitals? And would you likely see the opposite with maintenance companies instead of hospitals? Also I'd like to know more about how the refund of strength damage after combat works.

Lastly, I guess I'll add some information myself to return the favor. Regarding reinforcement bonuses, the Soviets have a crazy good idea for this (upgraded NKVD), which adds 30% hourly reinforcement chance.

[u/Aldrahill]

I am SHOCKED that this doesn't have more upvotes. This is a fantastic guide that will massively help you with your HOI4 strategy, watch it.

[u/georgioz]

When watching this I gained a 100% bonus to hardness

My sides hurt :D Fantastic video BTW similarly to the naval one. Great job.

[u/TheBlobber]

/u/-Reman

Timestamp 9:33 - Not quite sure where you are pulling the formula from, and I think you may be ignoring the cumulative nature of the problem.

I believe the mean time to reinforce should be determined as the mean (M) of a geometric distribution*, and so take value M=1/P, where P is the probability of success for a single trial (2% base chance to successfully reinforce per hour tick, and 7% with radio). This would give mean reinforce times of 50 and 14 hrs respectively, not the 34 hrs and 9.5 hrs claimed.

It is left as an exercise to the reader to determine the expectation value for reinforcement time of radio+signal companies.

Kind Regards,

The Blobber

[u/Killa567]

Nice guide, I have been looking for one that goes in-depth to the combat mechanics.

[u/carliboi]

Tl:dw pls