Hearts of Iron 4 (HOI4) – Best Air Doctrine – Gamer Empire

Doctrines are the part of Heart of Iron 4 that cause the most debates. Since you will always have to choose only one out of 3 or 4, players get really heated about which one is actually the most useful.

Most of the time, the right answer is: “the doctrine that fits your needs.” This is generally the right answer for air doctrines as well since the bonuses are very good no matter which doctrine you choose, as opposed to the land doctrines, where you should never pick Mass Assault.

Recommended Read: Hearts of Iron 4 – Warfare Guide

The first thing you will need to ask yourself is where are you willing to be weaker and what exactly do you want to gain from using your air force.

In this guide, we will go through all of the air doctrines in Hearts of Iron 4, explain why each one of them is very useful, and why, most of the time, Operational Integrity is the best one to choose.

What Each Air Doctrine Does

There are three air doctrines in HOI4:

Strategic Destruction
Battlefield Support
Operational Integrity

Generally, all doctrines offer very similar bonuses, which is why you can’t really go wrong here. There are only a few bonuses that are different, and those can make a big difference.

Here are all the bonuses that you get by investing in any of the air doctrines, that you will receive no matter which path you go down:

Air Superiority: +15%
Fighter Detection: +10%
Ground Support: +10%
Interception Detection: +10%
Naval Mission Efficiency: +10%

Strategic Destruction

As explained by the developers under the doctrine, Strategic Destruction is the go-to doctrine for people that want to destroy their enemies’ provinces using Strategic Bombers.

There are two choices you will have to make down this path, where you will first have to choose between better Fighter skills in Interception or Air Superiority missions, and then choose between a big flat bonus to Strat Bombing or a smaller one with a decreased night debuff.

Usually, if your goal is to bomb your enemies to hell, this is the right doctrine to choose.

Here are the exact bonuses you can get down this doctrine, ignoring the general ones we listed above:

Air Superiority: +15%
Bomber Defense: +25%
Escort Efficiency: +25% & Strategic Bombing: +50% / +40% & Night Time Strategic Bombing Penalty: -50%
Fighter Agility: +10%
Interception Mission Efficiency: +20% / Air Superiority Mission Efficiency: +20%
Naval Mission Efficiency: +5%

Battlefield Support

This is the doctrine to buff your CAS and deal crazy damage to the land troops below your air force. Or, at least, that’s how it’s described. If you actually look at the buffs, your CAS do become more powerful, but not enough to make a huge difference.

It does feel, however, that you are dealing huge damage to the troops on the ground, as long as you’ve got Air Superiority.

Here are the exact bonuses you can get down this doctrine, ignoring the general ones we listed above:

Air Superiority: +15%
Air Superiority Mission Efficiency: +15% / Ace Generation Chance: + 25%
Air Support Mission Efficiency: +40%
CAS Agility: +20%
Fighter Detection: +5%
Ground Support: +30%
Interception Detection: +5%
Strategic Bombing: +15%
Tactical Bomber Strategic Bombing: +10%

Operational Integrity

Weirdly enough, the Operational Integrity doctrine is described as the tactical bomber doctrine since it’s got a single Strategic Bombing boost for tactical bombers.

However, analyzing the doctrine better will likely make you realize that this is actually the best doctrine for fighters.

Most players in HOI4 want to make their fighters better than their enemies’, since this is the way you will win the aerial battles and gain the Air Supremacy needed to also get that intense CAS damage.

Operational Integrity gives you exactly what you need to effectively win in the air and get that Air Supremacy you clearly want over your land troops.

Here are the exact bonuses you can get down this doctrine, ignoring the general ones we listed above:

Ace Generation Chance: +20%
Air Superiority Mission Efficiency: +20%
Bomber Defense: +20%
Fighter Agility: +10%
Fighter Detection: +10%
Interception Detection: +10%
Interception Mission Efficiency: +20%
Strategic Bombing Visibility: -50%
Tactical Bomber Strategic Bombing: +20%

What Everything Means

Here’s a brief description of all the bonuses you can get with these doctrines so you can understand exactly what they do:

Ace Generation Chance: Increase the probability of generating aces during missions.
Air Superiority Mission Efficiency: Improves air attack, air defense, and agility for planes on this mission.
Air Support Mission Efficiency: Improves air attack, air defense, and agility for planes on this mission.
Bomber Defense: Increases the air defense for planes on Strategic Bombing mission.
Enemy Air Support: Modifies the negative effect enemy air superiority has on the combat ability of our ground troops.
Escort Efficiency: Reduces disruption from enemy attacks.
Fighter Detection: Increases the amount of detection planes on Air Superiority mission contribute to the region.
Ground Support: Increases the scaling rate of the Enemy Air Support bonus provided by air superiority
Interception Detection: Increases the amount of detection planes on Interception mission contribute to the region.
Interception Mission Efficiency: Improves air attack, air defense, and agility for planes on this mission.
Naval Mission Efficiency: Improves air attack, air defense, and agility for planes on this mission.
Night-time strategic bombing penalty: Reduces the negative effects of night for planes on Strategic Bombing mission, notably the Ground Bombing Targeting penalty.
Strategic Bombing Visibility: Counteracts enemy detection when on Strategic Bombing mission, reducing the maximum number of enemy planes responding to the bombers.
Strategic Bombing: Improves Strategic Bombing damage for planes on that mission.

What Is the Best Air Doctrine in Hearts of Iron 4?

Though all three doctrines are useful, depending on the country you select at the start, Operational Integrity will usually be your main choice for most countries, making it the best air doctrine in HOI4.

Most of the time, the most important thing in air battles is losing fewer fighters than your enemy. If you and your rivals place all of your planes in one air region, destroying more of their fighters to get Air Superiority is the way to go.

At that point, it becomes an attrition battle, where you see which one of you can keep destroying more planes, as bombers and CAS also get destroyed in the process. For this reason, Operational Integrity is the main doctrine to go for if you play as any minor country.

Since you don’t have the capabilities to build a large air force, your goal is to just keep your skies safe, to avoid the total destruction that CAS deal or the annoying Civ factory usage that bombers cause by leveling your country.

So, to avoid most problems, you just need to pick the Operational Integrity doctrine and send your fighters to fight. The Fighter Detection bonus, combined with Ace Generation and Fighter Agility, will make you the biggest power in the air.

71Cloak has made a video where he made nations fight with the same number of fighters and same tech, using different doctrines.

He pit Strategic Destruction against Battlefield Support, Battlefield Support against Operational Integrity, and Strategic Destruction against Operational Integrity.

In all scenarios, Operational Integrity lost 10 to 20% less fighters in the battles against the other doctrines, making it the superior choice for Air Superiority.

Which Countries Should Choose Strategic Destruction

Though Operational Integrity is the best choice for most countries, this does not mean you need to pick it. As you’ve seen from the stats, you just lose more fighters in the air battles, but this does not mean you lose if you have bigger production pools.

So, if you can afford to lose fighters and don’t care about losing more than your enemy, then you can pick one of the other two doctrines. This is usually the better choice for major countries that have huge production capabilities and can afford to lose thousands of planes.

Countries like the United Kingdom and the USA should always complete the Strategic Destruction doctrine, since they spend most of their time away from the fighting.

They also have amazing industries, allowing them to pump out as many fighters as it is necessary.

Destroying Germany’s industry is very important in taking them down, and the Strategic Destruction doctrine will help out a lot on this front.

This doctrine is also very useful for Commonwealth nations that won’t really be very involved in the fighting on the ground, but that can constantly pester Germany by bombing various different parts of Europe in hopes of destabilizing the country.

Most of America should choose this doctrine, unless they plan on attacking their neighbors. However, in most cases, even if you do attack your neighbors, Supply will be your biggest enemy, not air forces.

Which Countries Should Choose Battlefield Support

If you spend most of your time in huge land battles with your enemies, then Battlefield Support is a really good choice.

Though CAS deals a ton of damage even without this doctrine, this one allows you to quickly push through enemy lines with its amazing prowess.

A country like Germany, the USSR, and Japan would profit a lot from Battlefield Support, since all of them have to win their land battles first and foremost.

The only problem is that Battlefield Support gets the worst fighter bonuses out of the bunch, so you’ll always lose more planes than your enemies.

This doctrine will usually only be useful if you have a giant air force that doesn’t mind losing a lot, in exchange for huge wins on land. Or, if you have a really good fighter design, then you shouldn’t really be afraid of the air battles and just concentrate on destroying divisions.

Battlefield Support will make sure that the ground troops truly suffer if you’ve managed to gain Air Superiority, which should be easily done against the AI with enough research into Fighter and a design that focuses on Agility and damage.