Like most games developed by Paradox Interactive, Hearts of Iron 4 may seem intimidating to a beginner. Leading a country through the 20th century's greatest conflict is no easy task after all. One bad mistake can lead to certain doom for a nation that isn't careful. Myriad decisions, both large and small, need to be planned in advance in order to avoid catastrophic failures.

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Knowing the keys to success before starting the game can help immensely. Hearts of Iron 4 possesses many layers. Coordinating those layers, especially in the midst of war, can often be difficult. However, with the right information in hand, conquering Hearts of Iron 4 can become less of a headache and more of a breeze.

Updated October 24, 2022 by Mark Hospodar: Hearts of Iron 4 recently released its latest expansion, By Blood Alone. This DLC focuses primarily on Italy, which got a much-needed revamp to bring it on par with the other major nations. An Aircraft Designer was also introduced, allowing players the opportunity to experiment with different plane designs.

With every new DLC and update, Hearts of Iron 4 becomes a more complex game. Since the game continues to evolve, players could always use a few new tips to reflect the updated meta. As such, this list has been expanded to include several additional pieces of advice.

17 Guard The Coasts

Naval Invasion Of Great Britain From Hearts Of Iron IV

One aspect of the gameplay that many beginners tend to overlook and pros never ignore is coastal defenses. The attention this task entails obviously depends on which country the player is controlling. Landlocked nations need not worry about this problem.

Any country occupying a coast needs to implement some form of defense sooner rather than later. Unguarded shores easily invite enemy naval invasions. Build plenty of coastal forts and garrison the perimeter with second-line troops. Don't feel the need to construct a colossal chain of defenses. Even modest preparations can defeat enemy amphibious assaults.

16 Build A Variety Of Ships

Naval Combat From Hearts Of Iron IV

When playing as a major nation, it's vital not to neglect the navy. After all, why throw away a helpful resource? The key to any proper naval buildup is variety. New players learning the ropes may be tempted to just focus on one type of ship. However, that strategy isn't always very efficient.

A proper task force meant to engage the enemy should contain a healthy variety of ship types. Veteran players all have their preferences, but a good composition to aim for is around 4:1. In other words, there should be 4 screening ships for every 1 capital ship. Here's the breakdown of what constitutes screen and capital ships:

Screen Ships

  • Light Cruisers
  • Destroyers

Capital Ships

  • Aircraft Carriers
  • Super Heavy Battleships
  • Battleships
  • Battlecruisers
  • Heavy Cruisers

The reason for this variety is that each ship type has its own strengths and weaknesses. A task group only composed of one ship type can be outmaneuvered/outgunned by a superior enemy navy. A variable collection of ships, on the other hand, is ready for anything. In addition, submarines can be grouped separately to form "wolfpacks" to terrorize enemy convoys.

15 Close Air Support Is Essential

HOI4 Aircraft Designer

When it comes to deciding where to allocate military factories, players should never neglect close air support (CAS). Close air support directly aids the player's ground troops in combat by inflicting damage on enemy forces and also provides a bonus to Breakthrough and Defense.

Players will still need to produce enough fighters to defend their CAS, but focusing on the latter should ultimately be the priority. Building radar stations will also increase the effectiveness of all aircraft in range. With the new Aircraft Designer introduced in the By Blood Alone expansion, fans can make their CAS even more effective by experimenting with the different aircraft modules.

14 Train Special Forces According To Your Needs

Paratrooper Drop From Hearts Of Iron IV

In the race to churn out as much infantry and guns as possible, it's easy to forget about Special Forces units. Special Forces come in three varieties: paratroopers, marines, and mountain troops. To maximize the efficiency of these troops, it's best to look at the map and plan ahead. Play to each unit's strength and watch them go to work.

Let's use a naval invasion of Great Britain as an example. A German player will want both air and naval superiority over the English Channel (use that variable navy!). Marine battalions may want to secure the ports in preparation for the arrival of the main army. Paratroopers can also be dropped behind enemy lines to cut supply routes and hold major cities.

In this example, mountain infantry will not be very useful overall due to England's terrain. It's important to remember that players are limited to the amount of Special Forces units they can train. A cap limit is instituted, whereby Special Forces can't exceed more than 5% of the player's total battalion strength. As such, don't waste resources on training units you won't need!

13 Occupation & Collaboration

Occupation Mechanics From Hearts Of Iron IV

Occupation is now a more complicated endeavor in Hearts of Iron 4 than it was at the time of release. Players hoping to directly occupy every single territory they conquer are going to have to invest extra time and resources to make sure it's secure.

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A territory that's successfully occupied will yield more resources and factories for the player. However, clamping down on resistance effectively is essential. Otherwise, habitual sabotage by the angry populace won't do the player much good. A worthwhile alternative involves setting up collaborationist governments. Although players won't directly administer the territory, the headaches of collaboration will be passed on to a semi-independent puppet government.

12 Invest In The Intelligence Agency

Intelligence Mechanics From Hearts Of Iron IV

Utilizing one's Intelligence Agency effectively is yet another handy tool in a nation's repertoire. There are quite a few different avenues players can invest in, however, it's useful to decide ahead of time what kind of spy agency a player wants.

For example, if the player knows that they'll be occupying a lot of territories, it's beneficial to focus on the Defense branch. This specialization grants bonuses to anti-partisan activities and makes one's operatives more effective at rooting out resistance. As with all aspects of managing a country at war, the key is to play to one's strengths and stick with them.

11 Unlock Those Extra Research Slots

Research Slots From Hearts Of Iron IV

Research is vitally important in keeping pace with other nations in Hearts of Iron 4. Among other things, research makes industry more efficient and combat units more deadly. The faster a country can conduct its research the more of an edge it will have over its enemies.

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Large, more developed countries tend to start with three or four slots already unlocked. Small and less developed nations only start with two, thus suffering from a disadvantage. Regardless of the initial count, smart players should always prioritize National Focuses that grant an additional slot. Outproducing and outgunning one's opponents ultimately result in victory and research serves as the linchpin.

10 Always Prioritize Production Technology

Industry Tech Tree From Hearts Of Iron IV

Now, what to do with all those research slots? Technology that benefits the military should never be neglected, but neither should production. Efficient production is imperative for keeping those tanks and planes rolling off the assembly line in short order. Research plays a key role in maintaining that efficiency.

At least one research slot should always be kept open for an industry technology. Playing as an Axis country, it's typically a good idea to choose the Dispersed Industry tree considering the threat of being bombed is quite high. Allied countries, like the United States, can get away with Concentrated Industry. In addition, always prioritize Production, Construction, and Fuel/Rubber technologies whenever possible to stay ahead of the curve.

9 Save That Fuel

Fuel From Hearts Of Iron IV

20th-century warfare cannot be conducted without fuel. Nearly every unit in the game requires some degree of fuel, whether it be tanks, half-tracks, artillery, ships, or planes. If a nation's entire fuel reserves are depleted, units will still move but will start to suffer massive combat and speed penalties.

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As such, players always need to keep an eye on their fuel levels. Building synthetic refineries help, but fuel silos also need attention. Larger fuel silos mean larger amounts of oil that can be stockpiled for future use. Invading and occupying countries with large amounts of oil is also a helpful strategy. Don't let those tanks run dry!

8 Keep Training The Troops

Training Troops From Hearts Of Iron IV

Although there are diplomacy mechanics in Hearts of Iron 4, World War II will eventually break out at some point. A nation's military is going to play a pivotal role when it comes to either victory or defeat. Whether or not a player's military is already large or small at the start of the game, more is going to be needed regardless.

Starting in the 1936 bookmark is favorable considering it gives the player about four years to build up their forces. Infantry and artillery are vital, but tanks also need to be given some early consideration if practical. When upgrades are made make sure they go to the principal front-line troops that conduct most of the fighting. Garrison units don't need all of that fancy new equipment.

7 Exercise Those Troops

Troops Exercising From Hearts Of Iron IV

Countries that start the game with significant military forces (like Germany) should never be kept idle. Likewise, newly trained divisions should never just sit on their hands waiting on the front line. Assuming there is no imminent danger, land units should conduct military exercises. The same holds true for air and naval units as well.

Exercising consumes equipment, which can potentially slow down the training of new units and rolling out upgrades. Nevertheless, units that exercise will eventually reach the "Regular" experience level, making them more deadly on the battlefield. Exercising also accrues a small amount of Land, Air, or Navy Combat Experience, allowing for additions to be made to the divisional templates.

6 Consider Terrain When Deciding Combat Width

Division Template From Hearts Of Iron IV

The old debate regarding the pros and cons of 20 vs. 40 combat width is no longer applicable. The optimal combat width of a division isn't a cut-and-dry affair. Deciding on the best combat width for divisions now hinges predominantly on the terrain as well as the Reliability and Organization stats.

Some terrain types are better suited for smaller divisions, while others cater to larger formations. A player's chosen nation will play a role in this decision. For example, Japan and the United States will do a lot of fighting in the Pacific, where jungle terrain is common. Conversely, a country like Germany won't have to do much fighting in the jungle. This guide is extremely helpful for giving players a better idea of where to focus their efforts regarding optimal division templates.

5 Bank Some Extra Political Power Early

Political Power From Hearts Of Iron IV

Political Power acts as a sort of currency in Hearts of Iron 4. Spending Political Power is necessary when a player wants to perform an action such as changing a law or appointing a new advisor. A nation accrues political power gradually, but there exist other factors that can help speed up the process.

Generating large amounts of Political Power early can be extremely beneficial. Appointing an advisor that grants a bonus to Political Power accrual is a great first step. With more Political Power, more advisors can be appointed, which will benefit other sectors of the economy as well as war production. Draft and economy laws can be changed faster to a more war-centered footing, giving the player an edge over his opponents. There's no such thing as too much Political Power in the early game.

4 Get On A War Footing As Quickly As Possible

3D Models From Hearts Of Iron IV

World War II is going to erupt whether the player likes it or not. Being unprepared usually results in getting steamrolled by a tougher neighbor. Luckily, players have the benefit of hindsight when it comes to World War II. They have until about the start of 1940 to get their houses in order.

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Having extra reserves of Political Power can really come in handy here. Moving towards a war economy should be done at the player's earliest convenience to scale back consumer good consumption. Tougher conscription laws also need to be passed so that manpower doesn't become an issue. Appointing a political advisor that increases a nation's war support can be beneficial when trying to enact these changes.

3 Go For The Encirclement

HOI4 Encirclement

When it comes to defeating enemy forces, encirclement is the ideal scenario. Enemy divisions cut off from supply and fuel can't last. To achieve impressive encirclements, players may want to consider producing a few armor divisions with enough Breakthrough to overcome an enemy's Soft Attack.

Players may also want to consider that their tanks have enough Piercing to neutralize enemy tanks. By the same token, players should ensure the Armor value of their tanks exceeds their enemy's Piercing capabilities, although these considerations tend to be more applicable to multiplayer. With enough tanks to make a breakthrough and enough CAS in support, fans will be able to make substantial gains on the battlefield against the AI.

2 Prioritize Military Factories

Factory Distribution From Hearts Of Iron IV

Players have two basic choices when it comes to factories: civilian or military. Civilian factories increase the speed of construction and can also be used for trading with other nations. Military factories, on the other hand, produce all the necessary war material needed for the army.

In the end, military factories are going to have to take priority. Pumping out the vital equipment needed to win a war makes or breaks a campaign. This holds especially true whenever playing as a country where time is of the essence. Build enough civilian factories to fulfill the basic needs of trading and construction, then move forward with the military buildup.

1 Don't Forget To Trade (To Some Extent)

Trade From Hearts Of Iron IV

Trading in Hearts of Iron 4 is a pretty straightforward process. Players can give up some of their civilian factories in exchange for the resources they may need. Resources, like oil and rubber, play an important role in production. Not having enough resources imposes a penalty on production in certain cases.

Thus, it's a good idea to have some extra civilian factories so some trading can be accomplished. However, some deficiency in resources is still okay, even with the mild penalty. It's more important to use the civilian factories to construct other things one's country may need. Just keep things above water and don't feel the need to go overboard when it comes to trading.

Hearts of Iron 4 is currently available on PC.

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