Hearts of Iron 4 announced


I’ve been running a game as Canada in 1936.

So far, it has been about as entertaining as watching paint dry… but it has been a really good experience for me to understand the economy a little bit - civilian factories and trade, military factories and production - building things in provinces, research trees, national focus, etc. etc.

And then suddenly war breaks out in Europe and the game gets REALLY fun. Because I’m Canada, I don’t have much in the way of a military - but i’ve sent a fleet of like 9 destroyers and a heavy cruiser to Great Britain to protect convoys around the North Sea and also moved over my airforce of 25 naval bombers to hunt enemy ships in the same region. Finally moving over a meager 11 divisions to England to be ready to contribute to whatever.

I feel like I have a decent grasp on the naval aspects and the air-power - but I find the division designer and the groundwar to be confusing as hell. There are a million types of support troops, different tanks and mobile infantry options and i don’t know what is worthwhile (do i really need field hospitals?)


Yes. :)

When designing the division, you really want combat widths of either 10, 20, or 40 (the latter is typically only for later game and larger economies that can field very large armies). This is because the default combat width of a battle is 80, if I remember correctly. You want to maximize the number of divisions that can be firing at the enemy at one time. Having a combat width of 22 for each division would only allow 3 to fight all at once instead of 4, for example.

You want to watch your Organization. That’s the ability of your division to hang in the battle. Then you get into other details, like Soft Attack and Hard Attack. The former is the damage applied to soft (infantry) targets, the latter is what is applied to hardened units. When you build a division, you can see the Hardness percentage. A bunch of infantry will be at 0%, a division with some medium tanks and the like might be around 50%. If you are going up against a division with mostly soft attack, that 50% tank division is going to be very hard for them to damage.

Next up we have Breakthrough and Defense. Breakthrough allows you to avoid damage on the attack, defense does so when defending (shocker).

So what is worthwhile, when building divisions? It depends on the role of the division. Infantry provide the bulk of your Organization and have terrific Defense values which gets even better when they’ve had a chance to entrench. Their Breakthrough stat sucks though, which means if you assault with just Infantry, expect a ton of casualties and Org loss. But if this is a division intended to primarily hold a front? Infantry are great!

If you want to add a little punch to your Infantry division, take a look at Artillery. It provides more Breakthrough than another brigade of INF and has some good soft attack values. It’s able to punch, but the Org stat isn’t great so it lessens the division’s ability to take one. If you’re facing Armor, anti-tank guns give you the ability to pierce their armor (I’m going to avoid going into that with this post because your eyes are probably already glazing over) and provides important Hard Attack, so you can inflict casualties on the hardened portion of the division you’re facing. Anti-air helps protect from CAS planes and is most useful if the enemy holds air superiority and you’re unable to compete with Fighters.

The Support brigades you can add (up to 5, they’re assigned on the left-hand side of the designer screen) are important because they do not increase the combat width of the division. In that sense, they are “free” upgrades to the division, as long as you have the industry to produce the necessary equipment. They typically have low Org, but they bring a lot to the table. Anti-tank guns for armor piercing and hard attack, artillery for some damage against infantry, Engineers allow better entrenchment and lessen penalties crossing rivers, etc.

Now, those Field Hospitals? For most countries, they’re very important. Manpower is one of the most limiting resources for a lot of countries. Field hospitals allow you to return a lot of the casualties you suffer to the Manpower pool, I think it’s 20% for the first one you research. They also have the added benefit that those wounded vets returning to the front retain their experience, so your armies are better able to maintain their effectiveness compared to throwing green troops onto the front.

The Division designer and how it interacts with the amazing Production system is a very core part of the game, you can really dig deep into it as your understanding of the game grows. The “tl;dr I just want to get started” version is: stick to 20 combat width, use the majority of infantry unless you’re playing a Major and can afford tanks. Experiment with Support brigades.


This is really useful. Thanks for taking the time to write it up. Now that I know more I might restart as Italy and get myself involved in some ground wars to try and sift through all this information that you’ve shared.


When I played Canada, I found that the manpower restrictions were pretty severe. You probably don’t want to go too crazy about building a large number of divisions. Just try to build really effective divisions. Investing in airpower is also fun because it’s relatively easy on the manpower (and you don’t tend to lose it).

As Canada, I’m not sure I’d wait for the UK or the US to do “whatever”. I think it’s more fun to choose a target and do a naval invasion yourself. You have to be pretty selective in your fights though, so you don’t end up having to deal with a dozen full-up Panzer divisions. I think I had some success challenging the German takeover of Norway, and did some fighting in Africa.


Alright - good advice. And when I said ‘whatever’ i wasn’t trying to flippant and passive, I was mainly pointing out that i didn’t know what was happening :)

At the start of the game, you have a bunch of divisions that aren’t in armies. Is there any benefit to leaving them like that, or should I have them in armies and performing exercises no matter what?


You should always have divisions organised under some commander. I haven’t had time to play since the reorg of field marshals versus generals, so maybe there is an advantage somehow to just having divisions under an FM (though I would think FM + general should always be better). Never leave divisions without leadership thought. Having a chain of command always gives you bonuses. Field-training is also a great return for your investment. Veterancy is a huge combat advantage. There is no point in training once they are regulars though: it just burns your equipment.


New Dev Diary on Fuel

It looks like a pretty good system, and I’m glad that fuel use varies based on activity level (e.g. tanks that aren’t moving or fighting don’t use as much (any?) fuel and fighters on interceptor use less fuel than air superiority).

My major concern is whether the AI will be able to handle this. Already there are enough mechanics that can cause the AI to fall flat on its face.


Maybe this is where I hit a dead end with HOI4 - as the supreme ruler of a nation, do I really want to micro-manage division minutiae?


I don’t think this is going to greatly increase micromanagement, I see this having a larger impact on the strategic decision-making side. Things like “how many tanks can I really afford to field?” and “I’m going to build a few cruisers and destroyers for this patrol task, instead of more capital ships”.

I think there will be some additional “micro” when determining when to use heavy fuel-consuming forces. For instance, you might not want your huge carrier fleets sailing around non-stop if you have naval superiority. Maybe you notice your stockpile is getting low so you tell your strat bombers to chill out for a while.

We’ll see once we get it in our hands, but I don’t think it’ll add a bunch of tedious micro for me.


So this is something from the Paradox forum that I found really helpful that was posted by GAGA Extrem.

DEF - Defence - Used to deflect attacks when defending.
BRK - Breakthrough - Used to deflect attacks when attacking.
SA - Soft Attack - Used to attack soft targets.
HA - Hard Attack - Used to attack hard targets.
HARD - Hardness - Used to define how many % of the SA and HA of an enemy will actually be used against this division.
ARM - Armor - Average thickness of the armor for the division. If enemy can’t pierce you deal extra damage and take less.
PIER - Pierce - Used to penetrate Armor, if you can’t pierce your enemy, he will suffer less damage and he will deal more
SPD - Speed - Determines how fast the unit can move. High Speed gives a bonus to reinforce chance in combat.
MP - Manpower - How many men you need.
SUP - Supression - Used to keep partisan resistance in check.
REC - Recon - Used to determine which side has the initative, which gives a better chance to pick a good tactic.

Infantry (INF) - Your basic combat unit. High DEF, but low stats otherwise - Use as main body for your army.

Mountaineer (MTN) - Slightly better BRK than INF, but also much more costly - Use these for mountain warfare.

Paratroopers (PAR) - Weak stats and limited in terms of design options - Use them to snatch provinces to delay an enemy or cut him off.

Artillery (ART) - Very high SA, decent BRK, excellent firepower per frontage - Use them to increase your division’s SA and offensive capacity.

Anti-Tank (AT) - High HA and PRC - Use them to counter enemy tank divisions.

Anti-Air (AA) - High Air Attack, decent HA, minor PRC - Use them to shoot down enemy air units that attack in combat and get a bit of extra HA against enemy tanks, particularly LARM.

Rocket Artillery (R-ART) - High SA, decent BRK, excellent firepower per frontage. Almost the same as ART, but slightly better at offense - Use them to increase your division’s SA and offensive capacity.

Cavalry (CAV) - Good SPD, high SUP, subpar stats - Weak and more costly version of INF that’s faster and better at garrision duty - Use them to supress partisans.

Motorized (MOT) - High SPD- Faster version of INF - Use them to provide ORG for your tanks or for fast encirclement moves.

Mechanized (MECH) - High Hardness, good stats, high HA. Much stronger stats than MOT, but also way more costly and much slower - Use them to provide ORG for your MARM and HARM or to create semi-armored attack divisions.

Light Armor (LARM) - High SPD, high hardness, good BRK, low DEF, ARM, HA and PIER. Very low ORG. Weak against enemy armor - Use them for fast exploit divisions, to add BRK and a bit of ARM to your combat units or as breakthrough units against inferiour enemies.

Medium Armor (MARM) - Good SPD, High hardness, good ARM and PIER, balanced DEF/BRK and SA/HA, but low SA per IC cost. Very low ORG - Use them as Breakthrough units and to counter other LARM and MARM.

Heavy Armor (HARM) - Very high hardness, ARM, PIER and HA. Low SA per IC cost. Rather low SPD. Very low ORG - Use these to counter enemy tanks if you have too much IC for some reason.

Super Heavy Armor (SHARM) - Extreme Hardness, ARM, PIER and HA. Low SPD. Very low ORG. Insane IC cost - Use these if you are a maniac for whom HARM wouldn’t drain enough ressources.

Self Propelled Artillery (SP-ART) - Extreme SA, terrible HA, bad BRK, okay DEF, lower hardness, ARM and PIER. Trade stats for SA. Excellent firepower per frontage - Use these to give your tank divisions a big boost against soft targets.

Tank Destroyer (TD) - Good HA and PIER, terrible SA, bad BRK, okay DEF. Trade stats for HA and PIER. Rather low HA difference to regular armor - Use these to counter enemy tanks of a higher class (LARM -> MARM, MARM -> HARM) or better tech level.

Self Propelled Anti-Air (SP-AA) - Mediocre AA. Bad DEF, BRK, ARM, HARD, SA, HA. Trades stats for AA - Don’t use them - they are terrible.

Self Propelled Rocket Artillery (SP-R-ART) - High SPD and SA, decent BRK, excellent firepower per frontage. Lower ARM and HARD than SPART, but muchcheaper. An excellent way to add firepower to motorized divisions and a cheap way to add firepower to armored designs.

Engineer (ENG) - Better dig-in, better SPD and defence for some terrain, better attack for invasions. Later models increase dig-in significantly and give minor benefits for fort, river and urban combat - Use these to make your units significantly stronger at defence, particularly when defending a river. Remember that dig-in does boost ALL stats (and not just DEF) of a unit.

Recon (REC) - Better SPD in difficult terrain. Provides REC. Later models provide more REC - Use them to make your units a bit faster and pick better tactics slightly more often. Seems more important when your leaders are inferior (or just on par) to the enemy.

Military Policy (MP) - Improves SUP. Later models improve SUP bonus - Use these to supress partisans more efficiently.

Maintenance (MAIN) - Improved Reliability. Reduces equipment losses (including attrition and training). Later models increase reliability - Use these with your most costly divisions to reduce equipment losses.

Field Hospital (HOS) - Grants trickleback (returns some MP losses to your pool) and lower XP loss from combat losses. Later models improve trickleback and XP loss reduction - Use these to preserve precious manpower and boost XP gain from combat.

Logistics (LOG) - Reduces Supply Usage - Later models reduce usage further - Use these to reduce your supply weight and field more units inside a supply region.

Signal (SIG) - Increases Iniative, which givs a better chance to reinforce in comabt and improves planning speed. Later models grant more iniative - Use these to speed up your Battle Plans and to reinforce faster in combat.

Division Design Notes:

(1) Always aim for a width of 5, 10 or 20. The regular frontage in combat is 80 + 40 per extra attack vector (from a different province). Exceeding frontge gives you signfiicant combat penalties. Design with width 11 or 22 if you plan to attach the unit to a leader with Offensive trait (-10% unit frontage).

(2) Support brigades don’t increase frontage, so it’s a good idea to add ART (and maybe AT, AA) to all your designs. They don’t affect speed or hardness of a divsion, but do lower ARM and PIER.

(3) This means that a base design with 10/11 width has higher firepower per frontage than 20/22 (because you can squeeze in more support ART), but it also costs more equipment and Land XP to design (since most nations start with 8+ INF in their main template).

(4) Do not use pure Armor divisions. Armor has extremely low ORG and should be teamed up with MOT or MECH. Even when using the Blitzkrieg Doctrine Tree a pure Armor division will be barely more than a breakthrough unit that can’t sustain combat for more than a few days.

(5) SP-ART has, by far, the highest SA per frontage (followed by ART). It also needs far less equipment per brigade, so you actually pay ~30% less for it than for a regular ARM brigade, even if production cost per unit are the same. As of Sunflower (1.2), the equipment cost has been increased. They are still cheaper, but not that great of a deal anymore.

(6) Related to that: Support ART, AT, AA and R-ART need less equipment than Frontline variants (but also provide less stats). LARM, MARM and HARM also have different equipment numbers (60, 50, 40), so while '41 costs are 10/13/27 IC less per equipment, the total IC cost per brigade is 60 * 10 = 600 vs. 50 * 13 = 650 vs 27 * 40 = 1080.

(7) Remember you can use the DUPLICATE function to create new templates. Since every change to a template costs 5 XP per unit removed, exchanged or added (10 for support brigades), the duplicate function can save you a lot of Land XP. For example, if you want to have both LARM and MARM divisions with a few extra MOT, first finish your LARM template, then duplicate it and replace all LARM with MARM. That way you don’t have to add the MOT units to both templates.

(8) Any unit can capture territory, regardless of size. So if you want you can build single brigade MOT divisions to swarm out and capture territory. Just pray you aren’t stopped by a “real” division.

(9) ORG, ARM and PIER are calculated as an average (with some additional weights in it) of all your existing brigades. This means that adding a low ORG unit will lower your division’s ORG, while adding a high ORG unit will slightly improve it (same for ARM / PIER).

(10) ENG combines extremely well with a Defensive trait leader (+30% digin), even more so when the country also has Grand Battleplan (+10 dig-in) or Mass Assault Doctrine (+5 dig-in). France in particular can pull off some amazing dig-in values if they manage to grab the '39 model before the outbreak of the war - I have seen values up to 59% (just don’t ask me HOW it is calculated).

(11) A divisions armor and pierce are heavily dependent on the unit with the strongest stats. That means adding a single HARM or H-DT to a division will provide enough protection to be immune to any division that doesn’t use AT, TDs or MARM/HARM.

(12) When more comes to mind (or if there are some good questions in this thread), I’ll add it here.

Example Division Designs:
(Keep in mind these are just SUGGESTIONS to demonstrate how the system works, not necesarily the BEST DESIGNS). Support brigads are listed in [brackets].

Basic Main Combat Infantry:
10xINF [+ ART/ENG] (20 width)
Cheap and affordable, but not much else. Good on defence. Useful for poor minors.

Intermediate Main Combat Infantry:
7xINF + 2xART [+ ART/AT/EN] (20 width)
Same as above, but much better when attacking. Good for minors.

Deluxe Main Combat Infantry Division:
7xINF + 2xART [+ ART/AT/AA/ENG/LOG] (20 width)
Good all-around division that can fend off tanks on it’s own and even inflict minor losses to air units. LOG means you can squeeze in more divisions per Supply Region (great for GER / SOV / USA), ENG gives a good advantage when defending. Good for majors.

XL Deluxe Main Combat Infantry Division:
8xINF + 2xART [+ ART/AT/AA/ENG/LOG] (22 width)
Same as above, just with an extra INF to get to 22 frontage. Good for majors with an Offensive leader.

Mass Assault Division:
Adjusted template that adds a few extra INF divisions to make use of the -0.4 frontage reduction from the Mass Assault Doctrine tree.

Heavy Infantry DIvision:
6xINF + 2xART +1x H-TD [+ART/R-ART/ENG/LOG] (20 width)
A somewhat pricey, but extremely effective Infantry design. Protected against units without dedicated pierce and quite strong against enemy armor designs at the same time. A great option for late war countries like USA or SOV that have the time to grab HARM II tech before going into the fray.

Artillery Division:
4xINF + 4xART [+ ART/R-ART/LOG] (20 width)
Has lower ORG than regular Infantry, but more firepower per frontage. Good for breakthroughs.

Anti-Tank Division:
4xINF + 2xAT [+ AT/ENG] (10 width)
Great balance between SA, HA and cost. Keep them in reserve and use them in large stacks (8+) to halt enemy armored spearheads.

Anti-Air Division:
2xINF + 6xAA [+ AA/ENG] (10 width)
Low ORG, but high AA. Keep them as a reserve in the rear and strat redeploy them into important battles where the enemy airforce is harassing you.

Armored Spearhead:
2xSP-ART + 3xARM + 4xMOT [+ ART/AT/MAIN/LOG] (20 width)
Has great SA, good HA and decent ORG. A good spearhead and breakthrough division that can hold against counter-attacks.

Assault Gun Division:
4xSP-ART + 2xARM + 2xMOT [+ART] (20 width)
Incredible SA that rips through enemy Infantry, with (barely) acceptable ORG value.

Mixed Armor Division:
2xSP-ART + 3xARM + 1xTD + 3xMECH (20 width)
Mixed armor division that can deal with any situation.

Motorized Division:
A fast division with decent speed modifiers. Even rivers won’t stop these guys.

Security Division:
5xCAV [+MP]
Partisan supression unit

Garrison Division:
4xINF + 2xAA [+ENG/AA]
A defensive unit designed for island garrison duty where enemy air power is more threatening than tanks

Sorry for the spammy post. Some of this might not be optimal anymore, and I am a big supporter of having field hospitals in my divisions unless I play as the Soviets. I did however find this to be really valuable to help me wrap my head around division makeup.


This is useful for a noob like me. Thanks.

Restarted as Norway, and has been an enjoyable experience thus far. Got my navy bottled up in the Baltic Sea. The low manpower means that I have tried to focus on building elite divisions for the mountains, and then everything else I did was for the air force.

In 1941 the Germans and Italians finally invaded. My troop management was a mess, as the controls for managing the armies is not intuitive at all.

Still, my two mountain divisions bottled the enemy up in northern Norway. In Southern Norway the Germans pushed me back to Oslo, where I figured I was going to have to hold out with the hope that my air power (250 fighters, 100 CAS, 100 TAB) would let me hang on until the Soviets or the US caused enough mayhem to draw some troops away.

Instead, the enemy starting to try and push North, through Norway, leaving a long, straggling front line as they did so. I seized the opportunity to start rolling their flank and reclaim my ports with many 3 v 2 or 3 v 1 divisional matchups and overwhelming air power. A few months later I had completely driven them out of Norway.

Meanwhile, the allies had made a beachead in Amsterdam, but were locked in a stalemate. Moved my air force to an open air base there, and proceeded to tip the scales as the allies have broken through and started to retake Belgium and France.

Now I’m ready for my meager forces to try and move in and invade Denmark - but I can’t figure out how Naval Invasions work… so learning that will be my goal for tonight I guess.

After that I finally play a major!


Thanks for posting that! Yeah, some of that stuff is out of date, so don’t take their division design notes as gospel, @dionisus1122. The way special forces work now is very different and there’s been a fair amount of rebalancing in Waking the Tiger that makes some of the statements inaccurate. It’s a great read to kind of learn how to think about division design, you just don’t want follow his exact division makeups in all cases. ART has been nerfed for example, and AA is useful now in situations where you lack air superiority. Stuff like that.


A few bullet points to get you started:

  • There is a maximum number of divisions that can be assigned to naval invasions at one time, based on technology. If you try to exceed this it just won’t work, without clear feedback as to why your troops aren’t setting sail.
  • Move the divisions you want to participate in the invasion to a province with a port.
  • Select only those divisions you want to participate, then click the Naval Invasion button (looks like an anchor). You first click on the province you want to ship FROM, and then you click on the province you want them to land at.
  • The more divisions assigned, the longer it takes to plan.
  • You need to have ships in the sea “provinces” between your source and destination, otherwise they won’t launch.
  • Once the planning is complete (shown on a tooltip), click the green checkmark that tells your general to execute the plan. They’ll ship out and land at your destination.
  • This makes it sound way more complicated than it is. It’s pretty simple, but can be tricky to figure out how to do it the first time.


Yeah - I had figured most of that out, but what was confusing me was the ‘You need to have ships in the sea provinces’ bit.

The tooltip in-game for invasions says that you need to have air superiority or ships ‘running missions’ in the area. I couldn’t make heads or tails of this, because I had a large air force performing air superiority in that area, as well as ships on patrol in that area… but still nothing was happening.

I will try just dropping my fleet right there in the connecting sea province and see if that fixes it for me. I didn’t have much time to fiddle with it last night because it was the end of my session.


I think you need more than ships on patrol. You basically need to have a reasonable control of the sea zones.

From the wiki

In order to be allowed to execute the invasion, a country requires more than 50% Naval Supremacy (also called Naval Superiority in some tooltips) in all sea regions the divisions will need to cross in order to make a beachhead. Invading army will decline to embark on the mission with less naval protection.

Naval Supremacy over the region depends on the amount of ships on missions by the opposing sides, with a multiplicative bonus for air superiority. One fleet can simultaneously contribute to supremacy in up to 3 sea regions covered by its mission.

All ship classes contribute the same to the supremacy rating, a submarine being equal to a super-heavy battleship.

Ships on Hold or in ports do not contribute to the Naval Supremacy. Otherwise all mission types (formation spreads) contribute equally. Fleets on Patrol mission with Do Not Engage order contribute as well, even though they never engage in any combats.

Maximum possible bonus for Air Superiority is +100% to the ship amount, making each ship count for two. It is achieved when you have 100% air superiority and enough planes to cover 100% of the sea region.

Naval supremacy is only required for a short moment to launch the prepared invasion. After that the invasion will proceed even without sufficient supremacy.

Once the invasion has been properly planned, naval supremacy has been attained, and sufficient convoys are gathered, the plan may be activated.


It does look like a good system and I agree with Kevin the strategic implication are very interesting. That said I think it will severely hurt the Axis (it certainly did in real life) and so I wonder how the AI will be able to handle it. I hope they add the option to turn it off.


A couple of new developer diaries. The first is about the new UK focus tree, they seem to be pick on Alternative history. I love alternative history novels like the kind Turtledove writes, but I’m not particular interested in them in a WWII game. I sort of want to see a semi-historical game. I’m unusual in that feeling?

The 2nd is all about releasable nations. I don’t really care much about them in the context of WWII. On the other hand I think they are setting the stage for doing an interesting post WWII game early cold war game. All they have to do is expand the tech tree and now they have all this interesting countries to work with. Add some mechanics for the cold war using political points and it could be an interesting game.


I don’t think you’re unusual in wanting something semi-historical, but they were completely caught by surprise about how many people wanted more ahistorical options. Because of that, when they’ve revisited the old vanilla trees they have been adding in additional options for people who want to pursue a more off-the-rails approach. The AI won’t pick them unless you uncheck the Historical AI option and a player has the option of going down that path or not.

Personally, I enjoy semi-historical, but once I’ve done that a few times I like to start tinkering with “what if…” scenarios. I really enjoy keeping the AI on historical and going ahistorical routs myself.


I like having the options. I’m playing an imperial Germany game right now. It’s a new situation and it’s nice to have the position of Germany but not be playing Nazi’s. Now I don’t know who I will end up at war with first.

The Kaiserreich mod is a lot of fun for alternate history scenarios but the Expert AI support for that mod is an afterthought, and I find it hard to play without Expert AI.


Kaiserreich really is great.