Like most games developed byParadox Interactive,Hearts of Iron 4may seem intimidating to a beginner.Leading a countrythrough 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 to avoid catastrophic failures.
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Knowing the keys to success before starting the game can help immensely.Hearts of Iron 4possesses many layers. Coordinating those layers, especially in the midst of war, can often be difficult. However, with the right information in hand, conqueringHearts of Iron 4can become less of a headache and more of a breeze.
Updated July 27, 2025 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.
17Guard The Coasts
One aspect of the gameplay that many beginners tend to overlook and pros never ignore iscoastal 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 easilyinvite enemy naval invasions. Build plenty ofcoastal 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.
16Build A Variety Of Ships
When playing as a major nation, it’s vitalnot to neglect the navy. After all, why throw away a helpful resource? The key to anyproper 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, buta good composition to aim for is around 4:1. In other words, there should be4 screening ships for every 1 capital ship. Here’s the breakdown of what constitutes screen and capital ships:
Screen Ships
Capital Ships
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 begrouped separately to form “wolfpacks"to terrorize enemy convoys.
15Close Air Support Is Essential
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 theBy Blood Aloneexpansion, fans can make their CAS even more effective by experimenting with the different aircraft modules.
14Train Special Forces According To Your Needs
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, andmountain 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 arelimited to the amount of Special Forces units they can train. A cap limit is instituted, whereby Special Forcescan’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!
13Occupation & Collaboration
Occupation is now a more complicated endeavor inHearts of Iron 4than 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 ensure 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 involvessetting 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.
12Invest In The Intelligence Agency
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 whatkindof 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.
11Unlock Those Extra Research Slots
Research is vitally important in keeping pace with other nations inHearts 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 shouldalways prioritize National Focuses that grant an additional slot. Outproducing and outgunning one’s opponents ultimately result in victory and research serves as the linchpin.
10Always Prioritize Production Technology
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 imperativefor 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 technologieswhenever possible to stay ahead of the curve.
9Save That Fuel
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. Ifa nation’s entire fuel reserves are depleted, units will still move but will start tosuffer 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!
8Keep Training The Troops
Although there are diplomacy mechanics inHearts of Iron 4, World War IIwilleventually 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, buttanks also need to be given some early considerationif practical. When upgrades are made make sure theygo to the principal front-line troops that conduct most of the fighting. Garrison units don’t need all of that fancy new equipment.
