In part 2 of the tutorial (Land Combat), we examined land combat.
Land combat is probably the most important aspect of the military in Hearts of Iron 4. However, one should not underestimate the importance of air power.
Air power serves as a force multiplier for your land forces and as such, can be the difference between victory or defeat.
In this section of the tutorial, we will examine all of the basics of air power so that you can take advantage of all of your country’s potential.
Planning: What do I want my Air Force to Do?
There are several important aspects to consider when planning and building an air force in HOI4. Plane types, their stats, what missions they can perform, as well as basing and logistics all need to be taken into account if one is to utilize air power effectively.
Here we will go over some of the more important stats for planes.
Speed – Speed is important for almost all planes. Having a speed advantage over enemy planes reduces their ability to damage yours. It also increases your own damage against enemy planes.
Agility – Agility is how difficult your plane is to hit. Higher agility combined with high air defense will make your planes very resilient. Agility also affects how easy it is for your plane to damage an enemy plane, thus having high agility for fighters is key.
Range – Range is simply the operating radius of the plane. Planes assigned to air regions that are larger than their range will suffer mission efficiency penalties, which can be substantial.
Air Attack – Air attack is a measure of how much damage your plane can do to enemy planes.
Air Defense – Air defense is how much damage your plane can take before being shot down.
Ground Attack – Ground attack measures how much damage your plane can do to enemy divisions. This is both organization and strength damage.
Strategic Attack – Strategic attack is how much damage your plans can do to enemy buildings such as civilian and military factories, forts, refineries etc. It has no direct effect on enemy ground troops.
Naval Attack – Naval attack is how much damage your plane can do to an enemy ship. Especially important for any carrier-based planes.
Naval Targeting – Naval targeting is a measure of how likely your plane is to land a hit on an enemy ship.
There are 8 basic plane types in HOI4:
- heavy fighters
- close air support
- tactical bombers
- strategic bombers
- naval bombers
- scout planes
- and transport aircraft.
(There are technically more if you count the carrier variants you can build for some of the types). Jet aircraft and rocket interceptors aren’t really useful in the game so I won’t cover them in this guide.
Each plane type has certain strengths and weaknesses that make it more suited to certain missions and roles.
Fighters – Fighters are the most prevalent plane in the game. They are used to wrest control of the sky by shooting down enemy planes. They can also defend your own airspace against enemy bombing raids.
They have the highest speed and agility of any plane, which makes them ideal for this role. They can only perform air combat, however, are limited to air superiority and intercept missions.
Heavy Fighters – Heavy fighters have a similar function to regular fighters. They are designed to shoot down enemy planes in order to establish air superiority over your enemy.
There are a few differences though. Heavy fighters are slower and less agile than fighters but they have a much higher air defense. This makes them ideal for attacking enemy bombers when running the intercept mission.
Additionally, they have a much longer range than fighters which means they can function as fighter escorts for your own long-range bombers.
Close Air Support – These are rather short-ranged dive-bombers whose primary function is to support your army in combat by bombing enemy divisions. They have the highest ground attack score of any plane. They can also function as naval bombers in a pinch.
Tactical Bombers – A personal favorite of mine, tactical bombers are the jack-of-all-trades plane. They have a decent ground attack, naval attacks, naval targeting, and even strategic attack. This makes them capable of filling any bombing role you need them to, albeit worse than the specialized bombers.
Tactical Bombers have more than twice the range of close air support and naval bombers, which is another nice bonus.
Strategic Bombers – These are the big boys. Massive four-engine bombers that are expensive to build, but that can absolutely devastate enemy industrial output. Having decent air attack and defense means that, while they won’t be winning you air superiority, they are no pushover in air combat.
Because of their expense, they are not suitable for every country to build.
Naval Bombers – Curiously, naval bombers in HOI4 have a quite limited range, unlike their real-life counterparts. They make up for that though with the ability to shred enemy fleets. Having enough naval bombers can make an enemy fleet think twice about sortieing out. Unfortunately, they are unable to perform any other missions other than naval and port strikes so they cannot double as ground-attack aircraft.
Scout planes – Scout planes are used in HOI4 to gather intel. The intel gathered builds up slowly over time and acts as a bonus to your national intel on an enemy nation.
Having an intel advantage over your opponent gives your ground divisions a boost in combat performance.
Transport Planes – Finally, we come to transport planes. They are rather expensive to build but they allow for some key missions: Para drop and air supply.
Dropping paratroopers behind enemy lines can be effective if done right and under the correct circumstances.
However, the air supply mission is where they really shine. Transport planes allow you to have some room for error when it comes to supplying your troops. I build them any time I’m playing a major.
Now let’s look at the different missions your planes can undertake in Hearts of Iron 4. Note that not all planes can perform all missions.
Pilot Exercises – While not a combat mission, pilot exercise is a critical mission nevertheless. When running pilot exercises, your airwing will gain experience (up to ‘regular’ level). This is useful in peacetime to get your air force ready from the moment that war kicks off.
It will also generate a very small amount of air experience for your country. Keep in mind that this all comes at the cost of fuel spent and an increase in air accident rate.
Air Superiority – Airwings performing this mission will attempt to engage and destroy enemy air wings operating in the region. When you want to gain air superiority over an air region, this is the mission to run. Only fighters and heavy fighters can run this mission.
Air Intercept – A defensive form of air superiority, airwings running intercept will attempt to disrupt and destroy enemy bombers running bombing missions.
Keep in mind that your air wings will not engage enemy fighters. This mission is useful to defend your airspace from bombing attacks.
It can also be used if you are significantly outnumbered or outclassed by the enemy fighters and want to avoid them.
Close Air Support – Airwings running close air support will attack and damage enemy ground divisions. They will only attack if there is active land combat happening in the air region so you can’t set your bombers to ‘soften up’ the enemy before an offensive.
There is also a limit on how many of your bombers can attack the enemy which is based on the combat width size of the land battle.
In addition to the raw strength and organization damage they do, close air support attacks will provide a combat bonus to your ground divisions.
Remember that to be most effective, your bombers have to get through to attack without being disrupted. This means having dominance over enemy airpower in the region.
Strategic Bombing – Strategic bombing has no direct effect on land combat. Rather, it is the bombing of enemy buildings, infrastructure, and industry.
Within the strategic bombing mission, it is possible to prioritize targets to make your planes focus on radar, forts, airbases etc.
Targeting an enemy’s industry can cripple their war effort. Although, you should keep in mind that strategic bombers are quite expensive to build and that a fairly large amount of them will be required to inflict significant damage on the enemy.
Naval Strike – Naval strike is a mission that targets enemy ships in an air region over the sea. In order for your planes to actually attack the enemy, their ships must first be detected/found. If there is already a naval battle happening, your planes will automatically join the fight.
Thus, coordination between your air force and navy is critical for this type of mission. Naval strike can also target enemy convoys, although only those carrying troops.
Port Strike – Port strike also targets enemy ships while they are at base in a port. Therefore, a port strike must target a land region with one or more ports in it. Unlike other missions, port strikes require at least 30% air superiority in the chosen region before they can be launched.
Logistics Strike – Newly added in the No Step Back DLC, logistics strike attempts to choke enemy supply by targeting trains and trucks. If the enemy has a deficit of these in their national stockpile, their logistical capability will be limited. Keep in mind that if you want to damage their railways, you will need to run a strategic bombing mission.
Air Supply – Transport aircraft are the only planes that can run the air supply mission. The amount of supply that each plane can bring has fluctuated as Paradox tries to get the balancing right.
In any case, lacking range or not having air superiority will reduce mission effectiveness, which in turn will reduce the number of supplies that you can transport.
Air Recon – Scout planes are the only aircraft that can run the air recon mission. Each scout plane will slowly add to your country’s total intel on another country until it reaches the cap. The more scout planes you add, the faster the intel will grow.
Organization & Logistics
Now that we know what types of planes to build and what missions we want them to perform, let’s look at how to actually deploy and use them. Airwing size, air bases, radar, and spirits are all things to consider when using air power in the field.
Airwing Size – You can deploy air wings with just 1 plane all the way up to 1000 planes. So which size is the right size?
Most players like to use wing sizes of 100. This gives you flexibility allowing you to target multiple air zones. It also means you can stack airwings on air bases efficiently without suffering over-stack penalties.
All airwings must be of only one type of plane, meaning you can’t mix bombers and fighters in the same wing.
Air Bases – Air bases are needed to station your airwings. They can be built from the construction tab. Placement is important, as airbases will need to be in range of where you intend to launch your missions.
Each level of airbase can operate 200 planes. The maximum is level 10 for 2,000 aircraft. Stationing more aircraft than the capacity allows will lead to over-stacking penalties, which can be crippling to mission efficiency.
Carriers – Airwings can also be based on aircraft carriers. The amount of them is limited by the deck size of the carrier. Larger deck sizes means more planes.
Remember that only specific carrier variants of planes can be based on them. Regular planes cannot.
Radar – Having radar stations built in your territory will give a substantial bonus to detection. Detection, as we will see in the next section is crucial in air combat. Be sure to keep up with research and construction on radar if you intend to control the skies over your own territory.
Spirits – The No Step Back DLC added the officers tab. In this tab, you can select certain spirits for your armed forces using relevant experience. These spirits add certain bonuses to the branch ranging from increased research speed, faster training, mission efficiency buffs, etc. Be sure to look through them and decide which best fit your overall strategy for your air force.
Air Combat: Owning the Sky
Now that you have planned and built your air force, it’s time to put it into action. But how exactly does air combat work? The answer is a series of complicated mathematical formulas, the scope of which is a bit beyond this tutorial. This is the respective HOI4 wiki.
I will, however, give a general overview of air combat and how it works in Hearts of Iron 4.
As mentioned earlier, detection plays a critical part in air combat. Simply put, if you don’t know where enemy planes are, you can’t engage them. In-game terms the amount of air detection you have determines the number of your own planes that can engage the enemy planes.
For example, if the enemy launches a bombing raid over your territory and you have fighters set to engage, if you have low detection then none or only a handful of your fighters will actually enter combat.
Detection is improved by occupying ground in the air region (think having more ground spotters), having planes in the air region running missions, building radar installations that cover the air region, and by having certain doctrines and spirits. It is impaired by nighttime (-20%) and bad weather (-90%).
When your planes attack enemy planes they will use their air attack stat to deal damage to the enemy plane. If the damage done to a plane is higher than its air defense stat, it will be shot down. Planes use agility and speed to avoid being hit and to gain an offensive bonus against other planes. Once again, the wiki provides the actual formula if you are interested.
Shooting down enemy bombers is great but what happens much more often is disruption. Disruption occurs when bombers are engaged by fighters and forced to abandon their mission and return to base.
If air detection and fighter presence are high enough, it is possible to completely disrupt bombers and render them useless.
Disruption can be countered by ‘escorting’ bombers with fighter wings set to run the air superiority mission in the same air zone. This works by forcing the enemy fighters to also engage with your own fighters, thus freeing up your bombers from harassment.
Air superiority in HOI4 is simply the percentage of control over a particular air region that you have. It is a tug-of-war percentage of 100. Your air superiority score is increased by having planes running missions in the region. Even planes not running the ‘air superiority mission will contribute to this score.
Each plane gives 1 point of air superiority, however, there are exceptions. Heavy fighters give 1.25 and strategic bombers only give .1. Scout planes and transport planes provide none. Building static AA will reduce the enemy’s air superiority score.
An air superiority level of less than 40% is known as ‘red air’. 60% and up is known as ‘green air’ and 41-59% is known as ‘yellow air.’
Air superiority is vital in HOI4 because, for every 50 points of air superiority you have over your opponent, their ground divisions will suffer a 1% penalty to their defense and breakthrough stats.
Having air superiority will also affect enemy divisions’ movement speed making them slower (to simulate only being able to move at night etc).
So there it is; the basics of air combat in Hearts of Iron 4. You should now have everything you need to conceptualize, build, and use air power.
Use the knowledge to dominate the skies and remember the wise words of Field Marshall Montgomery “If we lose the war in the air, we lose the war and we lose it quickly.”