Tips After 300+ Hours Played

Hearts of Iron 4 (HOI4) is a strategy game that is build really for WW2 buffs who love strategy games and micro-managing. If you are NOT a fan of micro-managing, this is NOT the game for you. You will have to pause the game every couple minutes or seconds in order to close a dialogue prompt, check how your offensive is going, select new buildings to construct, choose the next research item, etc. . It is not like a typical RTS where you see your units dish out the combat on the ground and control individual grunts, but rather you are managing whole army groups and telling them to attack another army and you just see the "dice rolls" effects of whether you are winning or losing.

So, with that for context, I am going to give tips that I have learned so far about the game that I hope people getting familiar with the game will find useful.

NOTE: I will NOT go into all the basics of how the game operates for the sake of my personal time. But, I will try to give basic to intermediate tips to get you to a level to where you can enjoy the game!

In HOI4, you control EVERY aspect of your nation as it undergoes the trials of WW2.

To get a grasp of everything at your disposal, here is a breakdown of the building components in game:


Military Factories: These are your workhorses for you creating weapons, vehicles, and upgrades for your armies.


Civilian Factories: These allow you to build new buildings and upgrades in territories are the work horse for any and all buildings you want to create across the globe. The amount you have are limited by your Economic policy, and how many are used to "process" raw materials you trade for with other nations.


Naval Dockyards : Build your ships and fleets. Are also needed for repair and refitting.


Naval Bases : The higher the value of the naval base, the more supplies can be funneled into that territory for your land units.

Naval HQ : These give minor upgrades/advantages to your fleets depending on the commander assigned.


Rocket Sites: Like airbases but for rockets you build and want to launch.

Airbases: These not only "store" your aircraft, but their location adjusts what territories your planes can strike, depending on your air units range. They are also required to deploy paratroopers.

Supply Depots: Locations where supplies will be "built up" for distribution via rail roads.

Rail Roads: The higher the value, the more supplies can be delivered to the territories it passes through.

Radar: Gives advantages to air units fighting in same, or near, territories.

Tech Facilities: These allow you to assign/recruit scientists to build weapons and upgrades otherwise unobtainable in the normal tech tree.

Fuel Refineries : Gives you gas for your vehicles and the more you research certain items, the more fuel they give. Also with research upgrades, they can produce rubber as a raw material for your vehicles/units.

Fuel Silos: Increase the capacity of you max fuel level for your nation if you want to store up more fuel.

Infrastructure: Gives a nominal boost to troop speed but is mainly useful for giving more raw materials per territory and per level of infrastructure.

Sea-ward Bunkers: Gives defensive bonus against amphibious landing attacks.

Land-ward Bunkers: Gives a defensive bonus against land attacks.

Anti Air Emplacements: Gives advantages to air units in friendly territory, or works against you if it's enemy AA. Can also increase the risk associated with raids and deters raids in friendly territory per the AA level in a region.

Other building types I either don't use or are specialty buildings that I won't discuss further here.

Every "unit" you see on the map actually represents a whole division of thousands of men and equipment. Your job is to customize these divisions to your liking and KEEP THEM SUPPLIED!

I can not overstate how important supply is in this game and is the reason why I mentioned this game is very much micro managing. Without your divisions having proper levels of supply, they are basically useless both on offense AND defense. Therefore, any changes to a division template MUST be taken into careful consideration before saving the changes, as they take effect IMMEDIATELY to existing units NOT just new units of the same division template. Therefore, if you have only a dozen surplus artillery pieces and then assign all your regular inf divisions with support artillery or "line" artillery, then expect a MAJOR supply shortage.

In general, if you are planning to make any changes to existing division templates, it is best to start building a surplus first so that divisions avoid supply shortages and get a -50% combat disadvantage and thereby lose territory and men and possibly whole divisions.

If you want to really customize divisions, it is recommended to do so for special forces which already come blank as is or build entirely new custom divisions. The only modifications you should make to your existing divisions is either adding support artillery AND one or two line artillery to the template, depending on your artillery production level, signal companies, hospital companies, engineer companies (if not present already), and armored car recon. Recon gives you the best intel advantage in land combat and can not be ignored. I find that supply companies are not that useful if you have armies with commanders that have good enough supply skill as is. Helicopter support companies I would reserve for your elite divisions as they add a recon bonus and helos are just another thing to produce at scale that could otherwise be used elsewhere. You could also customize your armored divisions in leui of your special forces if you want a more "generalized" break-through division template, but just plan on either not building additional armored divisions to reserve surplus for existing unit replacements and upgrades, or build more only if supply allows for it.

If you want good break-through divisions, spamming artillery for marines or mountaineers is always a got to depending on the terrain. Doing the same for armored divisions but making the artillery motorized also has a huge offensive effect. Having assault engineers is also very useful but keep in mind that armored support vehicles are very costly to make and therefore assault engineers should be reserved for your breakthrough units.

You CAN have your regular infantry be your main offensive units, it just requires scaling your artillery production AND having air superiority bonuses to assist. Having some support anti-tank will help on the defensive in general. I have found that having support anti air really does nothing in air superiority both for your air power projection or reducing CAS effect for land divisions and may be a bug, so I would avoid assigning any AA support companies or line AA to any and all templates.

Typically, I find that heavy tanks are best for infantry based break through units since their is the bonuses from land combat your get from doctrines for infantry support for armor. But, you can also make cheap tank destroyers to obliterate armored divisions of your opponent if needed.

If you want to really have air superiority, I find that air defense is just a necessary for building your planes as is air attack or Ground Attack or strat bombing. Having "invincible" air units basically guarantees you a high k/d ratio and eventual air supremacy. In fact, if your strat bombers have such a high level of air defense (this is mainly for single player or playing against AI), I find that they rarely get shot down anymore.

I will be talking from the angle of you playing a major nation. My advice could be applicable to minor nations, but I simply haven't played with them much so I will just give that bit of precautionary warning.

During my time playing HOI4, I've noticed that by mid-game you need to be building more buildings, upgrades for territory, and factories than your baseline number of Civilian factories can handle. I find this especially true for Axis powers, as rebel damage to buildings can choke your build capacity to become a gigantic queue that your civilian factories either need to de-prioritize or chug through to get your nation/s working to top level.

I find that, if you are starting the game from 1936 on, it is best to actually split your civilian factories between building military factories AND additional civilian factories; with priority given to civilian factories. The idea being that investing in more civilian factories, though they are the most expensive, will have a "snow ball" effect mid to late game to where you avoid the aforementioned building problems and bottlenecks. Though early in the game your peace time economic policy will make any additional civ factories negligible, you will notice it once war comes upon you. If you know when your particular country is going to war, whether you be axis and attacking or allies on defense, I would recommend saving up enough political points to immediately change your national economic policy to wartime once war starts to receive the benefits of your well laid plans. Once war is upon you, I would either reduce or cancel whatever civ factories are in production in order to focus solely on territory upgrades and mil factories for supply.

Depending on your strategy for winning the game (as there is no one single strategy to win but there can be some deviations), you want to build accordingly.

AIR POWER

For example, if your nation is investing heavily in air power projection, CAS, or strat bombing, it is best to invest in building AA to help your air units dominate friendly skies. Also, radar gives advantages to this as well. If you have territories without an airbase, DO NOT build new ones as often you can convince an allied, friendly-neutral, or even straight neutral country to allow you to use air bases nearby via diplomacy and increasing their opinion of you to overcome whatever threshold there is for asking for air base access. Building your own simply takes too long and isn't worth the effort unless it is of critical importance for some odd reason.

NAVAL POWER

For the most part, you do NOT need to invest in additional dockyards or naval bases. Unless you face a serious supply shortage somewhere, then you can upgrade a nearby naval base to increase the amount of supply, but this is uncommon. For the most part, you can ignore building any additional naval building your major nation doesn't already have. The only exception is if you need a Naval Research center and I would only do this to unlock Anechoic Tiles for research for your submarines IF you have enough raw rubber to spare.

LAND POWER

If you plan on going mainly defensive, like playing Russia against the axis, or France, then I would recommend maxing out land-ward bunkers and territorial AA and radar in regions on the front line as this will cause the most damage to attacking powers. Don't be afraid to spam the max fort level on multiple hexes even if they are adjacent to each other as your armies are not invincible and may need more forts when they are overrun and fallback to the hex behind them. For the most part though, the game relies heavily on supply so building a reinforced electrical grid on a territory with high building limit and spamming mil factories on it is always your best bet. Build the electrical grid only if you plan on not having enough coal, or not researching coal upgrades as mil factories without enough coal power fail to perform after a time.

IN GENERAL

NEVER let your supply get too low for units. You can have level five railroads or whatever, but not having enough of a certain piece of equipment will severely limit your combat abilities on offense and defense.

Soft Attack is always king. Max it out.

AXIS

If playing as any Axis power, I would recommend strongly the building civ factories before war breaks out to avoid a bottle neck of endless building repair due to rebel activity. I find this especially true for Germany where you basically are forced to always have Brutal Oppression turned on for your occupied areas and wasting all your spies on uprooting resistance to allow you actually build stuff.

For Germany, your focus should entirely be on land and secondarily air power. Naval power as it is in HOI4 does nothing besides disrupt raw resource trade and allow for naval invasions which you will be doing nearly none of for the majority of the game. Having good armored divisions is key as your main opponent (Russia) doesn't have many hilly or mountainous areas which excludes the need for mountaineers. Really focus on breaking through with unstoppable armored divisions. Also, fuel is key so building a number of synthetic refineries before war breaks out will make or break your war effort early on. You can eventually trade for oil with Iran but may need to either invade them or defend them from hostile influence to secure your precious oil. Trading with Japan after they take the dutch east indies is also an option but may require building a lot of convoys to take the hit from raiding. In general, ALWAYS have a surplus of convoys to trade with.

For Japan, focus on controlling the sea with your existing navy and training them and using the up the fuel to make them Regulars to get the combat bonuses. If you build any ships, besides leaving the existing ships queued that have partial build bonuses already, focus on submarines as they build for cheaper in mass and can destroy most navies easily, especially once you get low sub visibility.

For Italy, basically do the same as Germany but your secondary focus should be naval power to control trade mainly and avoid naval invasion and rack up kills in the navy. Again, focus on building subs for mass production sake.

In general, having more allies than having to occupy more nations is better to avoid the supply hassle of occupation AND to have additional nations in your war efforts even though that's not entirely historically accurate (ie. Japan allies Nepal, Bhutan, Siam, etc., and Germany allies Portugal, Spain, Hungary, Bulgaria, Yugoslavia, etc.). Besides, as the Axis, you need to conquer the major powers anyways to win.

NOTE: I have noticed that Military Police does nothing really to suppression bonuses in a territory even when I hover over the occupation statistics for a territory and may be a bug in the game. Therefore, having MPs support companies is really useless besides the recovery bonus.

ALLIES

In general, you can avoid occupation policies as you will almost always be "liberating" nations that were previously occupied. Therefore, to get the manpower freed up, you can set it to either Secret Police or Local Police generally and change per nation as needed. Only set to Local Autonomy if you KNOW that the country won't entirely revolt and the integration bonuses will outweigh the unrest.

In general, keeping your allies in the game allows you to win. If both France and Russia, fall, you are kind of screwed as either the US or Britain unless you have already made substantial gains against a major Axis power, AND the game just becomes really long at that point given the Axis now have a huge increase in factories, supplies, and manpower now. So avoid losing both of these countries.

For Britain, sending most of your divisions to France to play defense helps prevent the fall of France and racks up a huge casualty ratio for the Axis early in the game. It also allows France to build up to slowly become more of a stronger ally later in the game. As Britain, your main concern is keeping your raw material supplies intact. Ensure your rubber producing territories in Asia don't fall to Japan later in the game, and crush Italy in Africa while they are distracted in fighting in southern France to avoid a protracted war to protect the Suez. Also, avoid making peace with Iraq once they join the Axis as to secure their oil fields once you turn your African divisions to deal with them. Also, since Britain will be interacting with the most capitulated countries in the game, increasing a counties legitimacy only gives you a few extra (weak) commanders that instantly go away once the country is liberated and one or two weak divisions you will need to supply with your own equipment. You political points are better spent boosting your own war efforts and nation.

Sea power is key for the allies but most major nations have large enough fleets to crush the Axis as is really but any additional ships should also be submarines for the mass concentration effect a mentioned with the Axis. Sea power is not only key for naval invasion for the Allies but also supply for both raw materials and lend lease. As an allied power, you need a large reserve of convoys to either send or receive lend lease at all times and for raw materials as you can not win the game really otherwise as any allied country either eventually needs some weapons from another or raw materials from another.

For America, you basically focus on having OP divisions once you join the war to crush the enemy. You do not need to spam divisions really as your allies likely already have plenty to play defense. Also, you can avoid penalties and having to wait to join the war by simply avoiding choosing "Limited Intervention" or "The Neutrality Act" until AFTER you ask Britain to join the allies once war with Britain and France breaks out. In order to do this, be sure to DELETE your original faction that is only just you and the Phillipines anyways. This allows you to help out earlier in the game (mainly in Africa and an earlier invasion of France as France will fall too quickly before you get there likely). You can then get the bonuses of selecting the Neutrality Act after already joining the war, which seems like a huge loophole in the game but hey it works.


As France, you basically are playing defense the entire time and trying to get enough national bonuses to give you political stability to avoid the factory output disadvantages from low stability. Focus on befriending countries and trying to get the focus "The Little Entente" finished asap so that Yugoslavia, the Czechs, Poland, and other smaller countries all gang up on Germany early in game while it is still relatively weak. I have seen this even trigger a revolt for a non-aligned Germany if you cause enough casualties and instability this way and knocks out Germany very early on to where you just focus on holding Vietnam afterwards from Japan. Build forts along the French border with Belgium and don't help it or the Dutch on defense as they will fall too quickly and you will find your units behind enemy lines.

As Russia, you basically focus on production and buildings on defense. It's not worth overthrowing Stalin as you lose most of your army in the process and your best commanders (unless you convince them to join the rebels) and it waste time. Build a bunch of forts on the Russian border and just amass there. The Fins are relatively weak and you can eventually send fresh divisions that way once you slow down Germany and trigger Finland to sign peace deal. Strangely, you can then increase their opinion with you almost immediately and ask for Lend-Leas from them to support your war effort. The war in the East is also crucial so either get neutrality deal with Japan to avoid raw resources being taken from you, or have a defensive line that can just hold Japan for the war. But, mainly, send most units west to fight Germany.