In Hearts of Iron IV, there are three distinct air doctrines, each of which will allow your nation to specialize its air warfare method and ultimately control the skies. Much like land doctrines and naval doctrines, each air doctrine is mutually exclusive and can’t be acquired in conjunction with the others.

Out of all nations, only Germany has an existing air doctrine (Battlefield Support) unlocked, so for the remaining other nations, they are practically a blank slate waiting for you to shape their future.

Strategic Destruction

Strategic destruction, as the description so aptly says, is mainly focused on improving the capabilities of your air force to conduct strategic bombing runs against the enemy's industry and infrastructure. The goal of this doctrine is to force the enemy to either surrender or be so heavily crippled that their army can no longer function properly.

Doctrine Strengths:

• Heavily favored are strategic bombers; they gain the most buffs out of all aircraft types.
• Also provides bomber escort bonuses; since the doctrine is focused on bombing enemy cities and factories, it makes sense that each bomber should be protected at all cost.
• Highest naval targeting bonus out of all doctrines; the naval mission efficiency here is 15% compared to 10% elsewhere.
• Great interception or air superiority efficiency bonus; depending on the path you take, you’ll get a strong 20% bonus in either category.
• Is the only doctrine to give nighttime bombing bonuses; no other doctrine has such a bonus in its path.

Doctrine Weaknesses:

• Poor fighter detection bonus; the bonus granted here is only 10% as opposed to higher values elsewhere.
• Is not good for air support missions; this doctrine provides no buffs for this type of mission.
• Lowest interception bonus; their bonus is the lowest out of all doctrines, regardless of the path taken.
• Fighters are the only aircraft to receive any agility bonus; the bonus here is only a meager 10% increase.
• There is no increase in ace generation chance; going through this doctrine will not result in more aces for your air force.

Why you should pick this doctrine:

• You intend to bomb the enemy into submission; this doctrine works best in this situation, like how Britain did in World War 2.
• You can maintain air superiority; this doctrine relies on air superiority in order to ensure that bombers are always escorted and won’t be shot down easily.
• You can play a patient game; since the doctrine’s goal is to slowly wear the enemy down, it will inevitably take some time to fully reap the benefits of your actions.

Battlefield Support

Battlefield support was the doctrine favored by the Germans during the Second World War. In this doctrine, close coordination between the CAS and land units is emphasized in order to commit the largest amount of damage to enemy units, thereby opening a soft spot to exploit. Some people like to call the CAS units "mobile artillery," thanks to how effective they were in supporting ground units.

Doctrine Strengths:

• Exception in ground support: as the doctrine title indicates, this doctrine received the largest bonus in ground support missions.
• Only doctrine to have an air support mission efficiency bonus, and this is at a whopping 40% increase.
• Provides unit bonuses to bombers; this includes both close air support units and the two types of bomber units.
• The air superiority bonus is still good; the bonus in air superiority matches the bonus given in the Strategic Destruction doctrine.
• Ace Generation Chance is increased exponentially in one path: the bonus here is a 25% increase, while the second best is only at a 20% increase in the Operational Integrity doctrine.

Doctrine Weaknesses:

• Not good in interception missions; as the doctrine emphasizes striking the enemy ground forces, they are not great at intercepting enemy planes.
• No fighter unit bonus; they are the only doctrine not to provide any agility bonus to their fighters.
• Not good in naval missions; they are paired with operational integrity for the lowest bonus here.
• No bomber defense; they are the only doctrine not to provide any bonus to their bombers in terms of defense.
• No escort efficiency bonus; this likely means that you’ll suffer more CAS losses if you cannot maintain air superiority.

Why you should pick this doctrine:

• You like a fast moving army; this doctrine suits a player with a blitzkrieg playstyle, as the ground support here is vital to keeping your armies moving.
• You wish for an immediate return in your air force; since the target is enemy ground forces, you’ll be able to see an immediate impact on your land wars.
• You have a great industry; the necessity of keeping your fighters and CAS units in top condition necessitates the need for a great industry as either can be easily shot down by enemy ground AA.

Operational Integrity

Operational Integrity is the final air doctrine on the list and focuses on improving the capabilities of tactical bombers as opposed to strategic bombers due to the latter costing more in production. Likewise, tactical bombers can also serve as a great alternative to CAS units thanks to their longer range and greater mission efficiency.

Doctrine Strengths:

• Tactical bombers can play two roles; they can be adequate in fulfilling both a CAS unit and a strategic bomber role.
• Air Superiority and Interception Efficiency Bonus at once; they are the only doctrine to give a buff in both missions at once.
• Reduces visibility for strategic bombing; this will lead to fewer losses on your side, and they are the only doctrine to provide this bonus.
• Agility bonus on fighters, tactical bombers, and strategic bombers: the agility bonus will allow units to last longer in fighters and outmaneuver enemy attacks.
• High Fighter and Interception Detection have the highest bonuses in either category among all doctrines.

Doctrine Weaknesses:

• Ground support is somewhat lacking; the ground support bonus here is just the same as the strategic destruction.
• There is no CAS unit agility; only fighter units and bombers receive this kind of buff.
• No strategic bombing bonus; they are the only doctrine to not receive any buff here despite using tactical bombers.
• Naval Mission Efficiency is poor; it matches Battlefield Support for the lowest naval mission bonus.
• The Air Superiority Bonus did not receive much attention despite efficiency seeing an increase; the bonus here is the lowest among all doctrines, making just half of the others.

Why you should pick this doctrine:

• You like having a more balanced air force; taking this doctrine will allow for a more spread-out bonus scheme without tying you down to a single unit.
• You like having air superiority; the great bonuses here mean you’ll have an easier time controlling the skies with your fighter planes.
• You prefer your support planes to have a greater range; this works well on certain battlefields as the range of tactical bombers is twice that of CAS planes.

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