Hearts of Iron 4 Construction

Economy is first up in this tutorial and that is no accident. Your economy is the foundation that your country is built upon in Hearts of Iron 4. Without it, you will struggle to conquer anything or worse, find yourself easy prey to be conquered by someone else.

I have divided this economy guide into 4 subsections:

  • construction
  • production
  • technology and
  • politics.

go to Part II of Hearts of Iron IV Tutorial: Land Combat


Hearts of Iron 4 Construction
Hearts of Iron 4 Construction

We will begin first with construction. You can access everything construction by clicking on the ‘construction’ tab at the top of the screen. Here you can decide which buildings to construct and where. You can queue up multiple buildings at once or build them one by one. Constructing buildings doesn’t require any resources. 

Buildings can be broken down into two basic categories:

  • production buildings
  • non-production buildings.

(There are also specialist buildings such as rocket test sites and nuclear reactors but these aren’t useful until the late game and even then on a limited basis). 

Production Buildings

Production buildings consist of

  • civilian factories (civs)
  • military factories (mils)
  • and synthetic refineries (synths).

These buildings all produce something. 


Civs are what you build with. They are expensive to construct (10,800 construction industrial capacity – CIC) but essential if you plan on building a lot.

Each civ provides 5 CIC (Construction Industrial Capacity = what you use to build.) each day and you can have up to 15 civs working on constructing a single building at a time. This means that with 75 CIC, it would take 144 days to build another civ. (This doesn’t factor in any modifiers like techs, advisors, infrastructure, etc).  

Civs are also used to trade for resources needed for production, but more on that later. 


Mils are factories that produce equipment for your armed forces. Mils can produce army equipment like tanks, small arms, trucks, and artillery as well as aircraft for your air force. Ships are produced at naval dockyards instead, which can only be built on the coast. 


Synths produce one oil and one rubber each. This yield can be further increased with techs found in the industry tab of the tech tree. We will discuss rubber and oil along with the other resources in the game later in the tutorial. 

Non-Production Buildings

Other than production buildings, there are several non-production buildings that can also be constructed by the player. 


Infrastructure represents the road network and electrical grid of a province and can be built up to a maximum of level 5. Higher infrastructure increases the amount of resources extracted, speeds up construction times, and improves supply throughput in that province. 


Railways are a new addition to the game in the No Step Back DLC. Railways are now the primary route for logistics in the game. A higher level railway (max. level 5) allows for much more supply throughput. Keep in mind that they need to be connected on both ends to a supply hub, however. 

Supply Hubs

Supply hubs are another rather expensive building (20,000 CIC). They are necessary, however, to supply your troops in the field. Fortunately, many countries begin the game with several already built so it may not be necessary to construct many, if any, additional ones. Naval bases serve the same function as supply hubs but over the sea rather than on land.

Air Bases

Air bases are needed to station your air force. They can be built up to level 10 with each level allowing an additional 200 aircraft to be based there. If you have too many air wings at an airbase, you will face stacking penalties. 


Permanent fortifications can also be constructed. Land forts help deter attacks from other land tiles while coastal forts do the same from attacks coming from the sea. Land forts do not have any effect on amphibious attacks and coastal forts do not have any effect on land attacks. 


Rather than boost your own troops’ defensive stats, forts reduce the opposing troops’ offensive stats. This is actually more beneficial as it can allow understrength, under-equipped troops to hold out against a superior force for longer. 


Radar installations provide intel on enemy forces and assist your air force in combat. When combined with static AA that can also be built in provinces, and your own fighters running intercept missions, it makes for an effective defense against enemy strategic bombing raids. 


Finally, there are fuel silos which are used to stockpile the fuel needed to power your aircraft, ships, and motorized land units. Fuel silos can be built up to a maximum level of 3 in any province. Each silo constructed allows for 100,000 fuel to be stored in the national stockpile. Fuel silos are only needed for fuel and not for crude oil, which requires no storage. 


Production is the part of the economy where ‘the rubber meets the road’ so to speak. It is the production of actual equipment, ships, and planes that will be used by your armed forces. It can be accessed by clicking on the ‘production’ tab at the top of the screen. 

Equipment is produced in the game in ‘lines.’ The player adds a military factory to one of these ‘lines’ to increase the production of the desired item. Each mil has a base daily production value of 4.75. This means that if you wanted to produce a tank that cost 14.25 production, it would take three days to produce using one factory. With three factories on the line, you would produce one tank every day. 


Of course, this is just the base production value. There are many modifiers (usually positive) that alter production value. Chief among them is production efficiency. Production efficiency is a measure of how good factories are at producing something. When starting a new production line, the base production efficiency is 10%. 

hearts of iron 4 production efficiency
Hearts of Iron 4 Production Efficiency

If you often modify what is being produced or change it all together, factories on that line will have a low production efficiency. Conversely, by producing the same thing over a long period, the factories on that line will gain production efficiency. Certain techs increase the production efficiency cap and reduce the penalty for switching production. 

Other factors can also influence your production including output, techs, advisors, national spirits, laws, etc. 


hearts of iron 4 refitting of older equipment
Hearts of Iron 4 Production screen

Recycling is good! Why let old equipment sit and gather rust in a depot somewhere when you can have it refitted into something useful!

Old variants of tanks and aircraft can be refit into a newer, modified version. For example, if you are producing Panzer IIs (light armor) and you unlock engine upgrades in the tech tree, you can convert the old Panzer II into Panzer II A’s. This comes with the benefit of lower resource costs and faster production time. 

However, you couldn’t convert the old Panzer II into, say, Tigers because Tigers are considered heavy armor which is a different equipment type in the game.

If you need numbers, you can keep older equipment in service alongside the newly produced upgraded variant. Just make sure the obsolete equipment variant is NOT ticked on the decommissioned tab. 


hearts of iron 4 Italy's lack of resources
Hearts of Iron 4 here Italy is lacking resources

Unlike constructing buildings, production actually requires resources. There are 6 basic resources in the game:

  • steel
  • tungsten
  • chromium
  • aluminum
  • rubber
  • oil.

These resources cannot be ‘stockpiled’ as in previous Hearts of Iron games. You must control territory that has them, trade for them, or synthesize them. 


Steel is by far the most common resource in the game. However, it is also the most used resource in the game. Almost everything from infantry kits to tanks to ships needs steel. Most of the major countries like Germany, the UK, and the Soviet Union have an abundance of steel so it isn’t normally a problem. Other majors like Italy and Japan may need to import it though. 


Tungsten is a hard metal that is needed to produce artillery, anti-tank guns, and tanks. Because of this and it’s a relative rarity when compared to steel, it is a vital resource and will play an important part in most games.

Iberia, especially Portugal, has large quantities of tungsten.


Chromium is not as common as steel in the game. Luckily it is not as commonly used for production. Only large ships like battleships and carriers and high-level tanks need chromium.

There is an abundance of chromium deposits in western Anatolia and the Balkans in the game. 


Rubber is needed to produce all aircraft as well as wheeled vehicles like half-tracks and trucks, thus it is of critical importance. It is found almost exclusively in the southwest Pacific islands which gives western Allied countries like the UK, France, and the Netherlands a significant advantage. 


Oil is not used to actually produce anything. Instead, it is used exclusively to convert into fuel to be used by aircraft, ships, and land vehicles. It is, therefore, perhaps the single most important resource in the game. Without oil, countries cannot operate a modern and effective military. 

Rubber and oil are different from the other resources in the game in that they are the only ones that can be synthesized. 


hearts of iron 4 Soviet Union's focus tree
Hearts of Iron 4 Soviet Union’s Focus tree

Each country in Hearts of Iron 4 begins the game with 3-4 research slots. You can usually add 1 or 2 more by completing certain focuses. Clicking on the ‘research’ tab at the top of your screen will allow you to browse through the different tech trees and choose what to research next. 

When you finish researching a new technology, a popup will come up on the screen showing you what you have unlocked. If it is a stat upgrade, it will have an impact immediately. However, if it is a new piece of equipment, you will still need to produce it. 

Design Companies

Each country has several design companies (some historic, some generic) that have an impact on research. Each company provides a boost to research speed as well as certain stat boosts for the relevant equipment item.

hearts of iron 4 France political
Hearts of Iron 4 France Tank Designer

For example, when playing as France, you can choose between five different tank designers. All five provide a +15% boost to research speed plus various other bonuses such as increased armor, speed, soft attack, etc. 

Only one design company can be active at a time so you will have to decide what your priority is. To get the bonuses the design company must be in place before you finish researching a tech but not before you begin to research it. This means that as long as there is still at least one day remaining to completion for a tech, you can still add a design company to get the stat bonuses. 

Design companies can be found by clicking your country’s flag at the top-left corner of the screen and are added using political power. More on that later.

High-Priority Techs

hearts of iron 4 important tech
Hearts of Iron 4 important tech

Each tech in the game has a year associated with it. For example, improved machine tools is considered a 1937 tech. Researching ‘ahead of time’ will result in a research speed penalty. Generally speaking, it is better to research techs ‘on time’ to avoid this penalty.

However, some techs are so crucial that they should be researched ahead of time. Techs like electrical engineering and computing machines allow you to research things faster so they are usually a top priority tech. 

Industrial techs like concentrated or dispersed industry, machine tools, and construction are all very important to your economy and thus usually worth it to research ahead of time. 

Finally, it is important to consider build time when thinking about when to research techs for aircraft, tanks, and especially ships.

If your strategy calls for, say, 6 divisions worth of 1940 tanks by 1939, then you probably need to have finished researching the tech by the end of 1938. (This is because once researched, you will need time to produce them in your factories).

Pro-Tip: Tech Juggling

One advanced strategy players use to research critical techs faster is tech juggling. Tech juggling works by deliberately leaving one of your research slots empty for up to 30 days, then using that ‘stored’ research on another tech.

For example, let’s say I wanted to research electrical engineering as quickly as possible. I would begin researching it in slot A while letting slot B sit empty for 30 days accumulating ‘bonus research.’ After 30 days have passed, I move electrical engineering from slot A to slot B and suddenly it has 30 more days of progress towards completion. You can then let slot A sit empty to generate 30 days of bonus research and switch back and forth.

As stated, this allows you to research crucial techs as fast as possible in the game. It does however have downsides. You are using two slots for one tech which means one fewer tech overall. Therefore it is advised to use this tactic sparingly. Losing one tech for the gain of getting another more important tech faster is only worth it in select cases. 


In the final subsection of this tutorial, I will cover politics. Politics in Hearts of Iron 4 includes choosing laws, decisions, and focuses and appointing advisors. These can be found by clicking on your country’s flag at the top left of the screen. Decisions are accessed by clicking the ‘decisions’ tab also found on the top-left side of the screen. 

The ‘currency’ or mana used for most political moves is called political power or ‘pp’ in the game. 


Advisors are your cabinet members and military high command. These people are ‘bought’ using pp and provide a wide array of bonuses from increased political power generation to construction buffs or experience gains for your armed forces.

Some advisors are only unlocked after completing certain focuses or changing your country’s ideology so check back if you think there was a new candidate added to the pool. 


hearts of iron 4 law screen
Hearts of Iron 4 Law Screen

Laws in Hearts of Iron 4 deal with things like conscription, economic mobilization, foreign trade, etc. Changing laws usually costs 150 pp.

Most laws provide bonuses as well as drawbacks. For example, you could increase your conscription law to a very high rate to get more manpower available for your armed forces, but this would come at the expense of your economic output simulating men leaving their jobs for the army. 

Some laws are only available if certain conditions are met like having a communist or fascist government, not being restricted by treaties, being at war, etc. 


hearts of iron 4 decisions
Hearts of Iron 4 Decisions

Decisions cost less than laws or advisors usually 50 pp. They have a smaller effect, however. Additionally, most of them are conditional requiring certain triggers to be available. For example, you can’t activate propaganda or sell war bonds unless you are at war. Many countries have unique decisions, some activated by focuses so it’s worth checking back often to see what is available. 


Your country’s focus tree can be found by clicking the flag in the top-left of the screen and then clicking on the ‘select focus’ button next to your leader’s portrait. 

By now, most countries have unique focus trees. Focuses offer a wide range of bonuses from tech speed increases to free factories and infrastructure. Focuses are also a vehicle (but not the only way) for countries to engage with one another diplomatically, offering non-aggression pacts, faction alliances, or even war ultimatums and declarations. 

Focuses usually take 35-70 days to complete and cost 1 pp each day. Some focuses are mutually exclusive so choose your country’s path carefully!


This guide has taken you through the basics of economy in Hearts of Iron 4. Economy is of critical importance in HOI4. Although the game has taken steps away from WW2 realism, it is still a game set during the WW2 period. As such, the war is a war of economies. The stronger economy always wins. Ignore it at your own peril. 

Here you find the Hearts of Iron 4 part 2: Military tutorial

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