This is a guide I'm making, feel free to comment below any questions or suggestions. I may update/expand this as I receive more feedback or ideas.

This isn't going to be a total guide to fix your individual issue, but should hopefully cover the most common ones. Please let me know any ideas or areas you'd like me to cover.

Here some some resources I've found to be helpful. If you have any to suggest, please comment below.


How to verify your game cache:
https://help.steampowered.com/en/faqs/view/0C48-FCBD-DA71-93EB

Good for fixing common technical issues. I recommend you do this first whenever you have a significant technical issue.


The hearts of iron 4 wiki:
https://hoi4.paradoxwikis.com/Hearts_of_Iron_4_Wiki

Good as a reference. Not perfect, as it can often be out of date or isn't fully explained, but great for getting a better understanding of certain mechanics.

Also good for cross-comparing things like doctrine or equipment stats without having to load into the game and hover over each thing.


Various YouTubers and other Steam guides:
Too many to count. You can generally get a good guide by simply searching something like "Hearts of Iron 4 (topic) guide"
Odds are someone has made one about the issue you're having, be it a certain country or doctrine.


Steam forums/Paradox Forums/Reddit:
If the things about didn't help you, try asking one any of these. Each one has its own community, so post at your own risk.

One of the most important things to do when asking for help on a problem you're having with the game is communicating it properly. There are several factors which could cause your problem, trying to isolate what is causing it is crucial to solving it.

If you're having technical problems, take note of things like what version of the game you're running, any mods you have installed, and what settings you have in place.

For in-game problems, there can be a dozen different reasons why you're getting pushed back or why your invasion isn't launching. Take screenshots of your battles, supply situation, air/naval zones, etc. Describe what you're doing, who you're doing it with, when you're doing it, who you're doing it so, and so on. Everything from doctrine, template, design, terrain, supply lines, focuses, decisions, and more can all dramatically change battles.

Don't be afraid to ask for help, but in turn be as forthcoming as you can with information. Help them help you.

This isn't a definitive list, there could be other answers to your problem, but these should help with the most common causes.


This is a big one. HOI4 is a complex game and requires a fair amount of investment to get into. My personal recommendations is to watch some youtube tutorials/gameplay and see if it's the right game for you. From there, you can play the in-game tutorial or choose an "easy" country, like the USA or Germany. Pick your battles, focus on doing one thing, your first run shouldn't be about trying to conquer the world.


Another very common issue for beginners. For your troops to attack, you need to be at war with the area attacking and attacking from an allowed area. Make sure you're at war with the target country (not just your faction or the country you're in) and make sure the land your attacking from is also at war. Your troops also need organization to advance, so if they're out, they're stuck. Make sure they're getting supplied.


This one could have a whole guide to itself. Land combat is complex and has multiple factors which can completely change the nature of a battle. To cover the most common problems:

-Check the terrain you're fighting in. Marshes and Mountains are much harder to attack in, especially with good offensive divisions like tanks. Also look for rivers, trying to attack across a river also inflicts debuffs and can change combat width/tactics.

-Supplies are key to any offensive. Check your supply situation (press F4). If you're low on supply, capture hubs, increase the infrastructure/rail lines in the area, reduce the amount of troops you have, or add supply companies to your divisions. Look before you leap. When doing naval invasions, make sure you capture a port. When doing land offensives, take note of the range of your supply hubs and where theirs are located.

-Air support dominates both land and sea. Having planes in the sky affects the troops below. Air superiority by having fighters up (green/red air) will debuff enemy troops in the zone below. Having close air support will not only buff your troops, it'll deal direct damage in combat, meaning that even weak divisions can push against much stronger ones in normally unfavorable conditions. To counter, make sure you produce enough fighters, capture enemy airfields, and add support-AA to your divisions.

-Strength. Make sure your divisions are fully equipped. If you're out of guns, your troops can't do much. Also applies to manpower. Don't waste lives or equipment. Tanks are expensive, lives are too. Once you're low, it's hard to dig yourself out of the hole, as your divisions will do worse.

The army is the key experience for many HOI4 players. It's easy to get confused with all the different mechanics all coming together in one big battle. A few things to keep in mind:


It used to be that the answer to this was resoundingly 20 or 40 width. These widths used to perfectly fit in combat on all terrains, so they were the optimal size for fitting as much firepower into the division as you could.

With No Step Back, the developers intentionally made it so that there is no best combat width for every situation. For example, plains and deserts have a combat width of 90, so a 30 width tank template would be good, as you could fit three divisions into combat without any penalty. However, Forests and Marshes have a combat width of 84 and 78, respectively. Meaning that tanks that are optimal for fighting on plains and the desert would receive some penalty fighting in forests or marshes, in terms of combat width stacking. (Tanks get additional penalties to some terrain regardless of width)
Mountains have a base width of 75 and increase by 25 for each additional tile, meaning that 25 width divisions are optimal for fighting in mountains, but generally speaking it's best to keep your divisions "pure." Infantry have a base width of 2, so odds are you'll be using 24 width infantry/Mountaineers. Or add 1 line arty and make it 25.


That general is set to an area defense order. By default this triples the amount of divisions the general can hold without penalty. If the general has skilled staffer (24->30 divisions), they can hold 90 divisions on area defense orders. You can set more troops to these generals, but the benefits gained will be reduced, so I'd recommend you hire more generals and spread out the troops.


Pre-La Resistance DLC, you used to have to station troops physically around the areas you controlled, which was annoying to manage, slowed the game down, and wasn't fun to deal with.
Nowadays, you automatically garrison the area, "off-map" and try to reduce resistance and build compliance. This happens without you needing to do anything other than hold the land, so focus on winning the fight. You can change your occupation law to reduce resistance or have a softer law, which increases compliance. Eventually you'll want to reduce your law so you can build enough compliance to reap some of the benefits of occupying the land, but you need the guns and manpower to do that.

As to what division to use, the cheapest one is a pure cavalry division. This only requires guns and most countries start with a cav division, so should be cheap EXP wise as well. Remember to remove any extra support companies (recon, arty, engineers) when assigning the template to act as MP.

MP support is effective, but more expensive. It requires support equipment which can often be better used supporting your frontline troops. Additional research makes it more effective, later game.

Once you have more of the world under your boot and have the IC/EXP/research to deal with it, you might want to consider adding tanks or armored cars to your MP divisions. This increases the hardness of the division and will reduce the losses they take in high resistance areas. The mechanic here is hardness, not armor. Hardness is how much of the division (percentage) is "armored," versus "armor" which is the divisions ability to fend off piercing attacks.
In other words, it's best to have the cheapest tanks/armored cars for these divisions. Increasing your armor won't help here. If you're trying to balance it, economically, I use cavs until I fully switch to medium tanks, leaving 1-3 military factories producing light tanks to later act as MP.

In short: Cav -> Cav/MP -> Cav/MP/light tanks, each step optional. Just make sure you're not wasting your good tanks or arty on occupational forces.

The Navy is arguable the hardest and least understood aspect of the game. It's a common joke that no one really understand the naval system. Again, this is another topic that could have its own guide, so I'll try to limit it to a few FAQs.

I'll also note that what I put here is what I personally do, there are various playstyles and options that might work better for you, or might change overtime as Paradox balances the game. If anything I say is inaccurate, please let me know below.



Most common causes are either airpower or lack of screens. If they have naval bombers overhead, they can damage your navy without even getting into a fight. If you don't have screens covering your capital ships, torpedoes will shred them. Ensure that your fleets have air cover and your capital ships are properly screened. (I would suggest at least 4:1 screens:capital ships)



Odds are you've set them all to "Patrol"l, which means they're out in the ocean, burning fuel, looking for the enemy. You don't need your slow battleships to go hunting, send your fast light cruisers out in a separate patrol and set your main fleet to "Strike Force"
Also worth noting that bigger ships burn more fuel. If you're having trouble managing this, import more oil or research better fuel options. You can also change your economy/trade law. Finally, try shifting to cheaper, lighter ships, like destroyers and submarines.


Check that you have dockyards assigned to repairs and see where your ships are, physically. If they're in a low level port, they're limited in how many ships that can be repaired at the same time. (A level 1 port can only repair 1 ship at a time, a level 6 port can repair 6 ships at the same time, etc.)

Build and assign more dockyards to repairs, move the fleet to a higher level port, and make sure they're not getting hit via port strike from enemy naval bombers.

This is the way I deal with most enemy nations as almost every country. Again, you don't have to do this yourself, but this should provide an easy template to expand upon once you've got the mechanics better understood. Spam out NAV/TAC bombers. Take your initial fleets and combine it into one big deathstack (or two). Filter out any submarines into a separate Admiral and split them again until each task force has fewer than 10 submarines. Assign your submarines to convoy raid zones outside the air range of the enemy nation.

Balance your initial stack. About 4:1 screens:caps, then create a few task forces for specific roles. If you're facing an enemy with submarines, make a few destroyer-based TFs with convoy escort. If you're expecting to do some naval invasions, have some older Battleships/Battlecruisers set to naval invasion support.
Take your newer light cruisers and have them patrol for enemy fleets. Your main stack set to strike force will provide naval superiority and will fight once your cruisers have discovered the enemy. Your naval bombers (and TACs if you're fighting in longer range zones) will chip away at enemy ships while your fleets hunt them down. Hopefully your submarines will raid their convoys, reducing their war support and resources.

The airforce is extremely important for supporting your industry, alongside your land/naval forces. As the loading screen says, "If we lose the war in the air we lose the war and we lose it quickly.- Bernard L. Montgomery"

(I'll also note that I don't have BBA, so I can't comment on the air designer... so this section is currently more of my opinion on a few subjects.)

Fighters.
Fighters are the most important air unit for basically every situation. If you don't have enough fighters, the enemy fighters will shoot down the rest of your airforce and then you'll have nothing.
Having just fighters is still a significant boost to your other forces. It'll debuff enemy divisions and increase your naval superiority.


Depends on how you use it. Also depends on who you're playing and who you're fighting.
Historically it was used only by rich nations with enough industry and fuel to make numerous, massive planes drop numerous, massive bombs and hope to hit the right city. It's an expensive process which requires significant investment. However, if done properly, it can help trap the enemy in a downward spiral or give you the advantage you need to make a strong push.

IMHO, there are two ways to approach it. Either a "light" investment, like making a fair number of TAC bombers or a small number of strategic bombers, and using them to do things like bomb Pacific islands or target airfields/supply hubs near combat zones. This is effective by denying the enemy air support and reducing their logistical capabilities. This doesn't require too much research/IC/fuel/etc.

The other option is to go after their industry which requires more bombers and more dedication. Your air doctrine here really matters. Going Strategic Destruction and choosing Day Bombing gives you a massive +50% bonus to strategic bombing which makes a huge difference when you're sending 1,000+ bombers out to destroy the enemy's war industry. This is only really worth it as the USA or as alt-history nations, in my experience. Remember to target their airfields first. You need to cover your bombers, as enemy fighters and disrupt and shoot down your bombers, meaning you're wasting IC for nothing. Once you've got them in a downward spiral (i.e you've bombed their factories so much they can't make enough fighters to stop you from bombing them even more), you can try to whittle away their conventional forces via other means.


In general, no. The range of tiers 1/2 of rockets is comically small, being only 500/640 kilometers. The amount of damage they do is also small and rarely worth considering.
Tier 3 rockets have considerably better range and thus have a few uses. As a "free" air wing, they can be used to harass enemy back lines. I'll build a handful, late game, just to make sure every air zone the enemy has is getting at least some form of coverage.



Nukes are a powerful tool, but they aren't the world ending ICBMs we have today. They're expensive to research and build, requiring late game research and numerous building slots to be effective.
Researching level 1 of nuclear research only grants a research bonus. Level 2 lets you build reactors but until you research level 3 they don't produce anything/ Once you research level 3 (properly unlocking nuclear bombs), each reactor will build one nuke per year. So if you have a dozen reactors, you can drop a nuke every month. Note that nuclear reactors are extremely expensive, more than twice as much as a synthetic refinery and more than four times as much as a military factory. You can also only build one per region, so you are fairly limited in the number you can make.

As to actually using them, note that dropping nukes in-game does no permanent damage to cities and is more of a "tactical" solution to your problem. Dropping a nuke directly reduces the war support of the country you drop it on, depending on how much damage it actually did. This means that the areas you've already been strategically bombing where all the buildings are damage won't reduce war support.

One of the lesser known and one of the most powerful features of nukes is that dropping it on an airfield will destroy the planes located there. So if the enemy has 2,000 planes sitting on an airfield, get 75% air superiority and drop on a nuke on it and instantly delete a massive portion of their airforce. Repeat as needed.

As for land combat, there are two options. Dropping a nuke on enemy divisions will cut them roughly in half and damage any forts on the tile. You can either use this directly for combat (such as dropping it on a tile you land on before you launch your naval invasion) or you can try and deplete their manpower/equipment.

Divisions cut in half quickly become a massive void for manpower and can lead to enemy nations running out of men by trying to refill numerous deplete divisions. Or you can focus on expensive divisions like tanks and try to get them to run out of equipment. Once they're in a good deficit, your troops should be able to push without issue. The AI will often stack large numbers of divisions on borders, making this a perfect way to deal significant damage to them without needing to move a single division. Find a tile with a good number of divisions, drop a nuke on it, then repeat as needed. Look for multiple tiles so you can spread out the damage to better equipped divisions. Give the divisions time to refill, then strike again.

You have various laws which impact how your economy, army, and resources are used.

Conscription law determines how much manpower you have.

Your economy law determines how many factories you can dedicate to the war effort, among other things.

Your trade law determines where your resources you extract go.


The easiest option is to increase your conscription law. Upto Extensive Conscription, there is no real downside other than losing political power. After that, you run into issues with your construction speed and production. Sending your factory workers to the front line makes it harder to produce things.

If you're playing a smaller nation, consider adding a field hospital support company to your divisions.

Otherwise check for things like making sure you're not getting convoy raided and that your occupation areas aren't in death spirals (seriously, this is a major one, if you have massive resistance then you're going to be losing a lot of men and guns.) Stop fighting until you can get your pool back up. Make sure you're not attacking mountains, forts, across rivers, or into enemy controlled air zones.


It's almost always better to increase your economy law. Once your war support goes up, it's generally the best use of your political power to up your economic mobilization. The exception is Total Mobilization. It's the best economic law in terms of civilian factories at your disposal and military factory construction speed, but comes with the massive downside of a -3% recruitable population. If you're only on Limited Conscription (or one below that), you'll quickly hit negative manpower, rendering your army depleted. Either get a bonus to your recruitable population (such as the decision Women in the Workforce) or only use it when you have a high enough conscription law.


Check your trade law. Having it set to Free Trade will take 80% of the resources you extract and put them up on the market. Other countries can buy them from you, giving you civilian factories, but if no one is buying it goes to the free market. If the war kicks off and you find yourself running out of resources, change it down to Export Focus/Limited Exports. The benefits from having a high level of trade law are nice, getting additional factory output, construction speed, research speed, and so on. But if you're wasting all your civ factories buying resources you're already extracting, it's worth paring down.


In my experience, they're only really worth it as Germany. They get a strong bonus to their rubber production, have plenty of building slots/IC, get bonuses to research, and have an excess of everything else. Building a refinery costs more than a civilian factory, which makes it a question of it is worth building versus building a civ and trading for rubber/oil. Refineries cost a lot of IC and research, but if you're playing a country that is locked out of these critical resources, they can be a life saver.

A variety of reasons.
-The game has changed significantly since the initial release, the video could be from an older version.

-Mods. Some mods change only a few things (like a specific mechanic or visual). Other mods revamp and overhaul the entire game. From entirely new tech trees, to expanded vanilla mechanics, to totally new scenarios like Old World Blues or Kaiserreich.

-DLC. The mechanic/focus tree you're looking for might be part of one of the several DLCs release that changes the base game. Notable features include the tank/plane/ship designers, spy missions, most minor country focus trees, and various tasks like minelaying, recon, and logistic strike.

Oil and fuel are frequently used interchangeably, but are not the same thing. Oil is the resource you extract out of the ground. Fuel is the thing you put into your tanks, trucks, planes, and ships to make them go. The general idea is that oil = fuel, but there is a little bit more to it than that. Some things affect only oil or only fuel, and should be noted. (This didn't always use to be the case, as pre 1.6 oil was used to produce equipment like steel or rubber.)

For example:
-Your economic law changes how much fuel you get per oil. Anything below War Economy means you're losing fuel.

-Refineries produce rubber and fuel, but not oil. This means you can't build refineries and hope your allied nations can trade with you. You have to lend lease fuel directly to them.

-Things like bonuses to research for synthetic refineries should be balanced with other resource extraction research or things like logistic support companies (If you're playing a country with fuel from refineries vs fuel from trade vs fuel from extraction)

There are two kinds of Anti-Air, each with their own use. Equipment-AA is produced with military factories and given to your troops. This helps reduce the penalties on those divisions when moving over land or fighting in combat. This only applies to the division it is in, so it's best used as a support. It's not worth having multiple stacks of AA in its own division, trying to shoot planes down. Equipment-AA helps shoot down CAS/TACs going for your divisions, but won't touch Strategic bombers.

State-AA or Static-AA on the other hand is used to fight the larger, strategic bombers flying high overhead, bombing your factories. Many people feel they're not worth it, but I'll build them on rare occasion when fighting a long war against numerous enemies that have a large air force. It also helps with fighting enemy port strike missions. So it can be worth building AA in areas where you're repairing your navy or hold numerous factories. I've used it most (in unmodded worlds) as Germany, fighting against the large airforces of the UK/US trying to bomb the mainlands of Europe while I try to focus on knocking out the USSR first.

I plan on updating this guide some more, both in content and format. If I made any mistakes, please let me know and I'll correct them. If there are any topics you want me to cover or change, comment below.