Hearts of Iron IV Guide | Naval Doctrines & Spirits

Hearts of Iron IV has many nuances and factors involved in how its armies and navies work. The navy is one of the game's simpler elements. Despite this, at first glance, things can be very overwhelming and hard to understand. DLCs like Man the Guns add a lot of new things, such as ship designs.

There are a lot of factors going into making your navy good, and one of the main ones is the Naval Doctrines. Another is the Naval Spirits. Doctrines are three mutually exclusive trees that let you specialize your naval forces towards a certain niche. Each doctrine in a tree costs around 100 Naval XP to unlock; however, these are almost always affected by various modifiers ranging from tech, focuses, national spirits, advisors, and theorists.

The base game has three doctrines that you can play around with and select from, each boosting a certain section of your Navy.  These are Fleet in Being, Trade Interdiction, and Base Strike. Now, all of these are at least somewhat emulated from real-life naval doctrines. Fleet in Being in the name is the doctrine followed by the British and Americans in World War 2.

However, for the Americans, it later changed into a Base Strike. Meanwhile, Trade Interdiction stems from German U-boat tactics. Finally, Base Strike is built on the Japanese ideals of Kantai Kessen, or decisive battle.

Naval Doctrines

Fleet in Being

Fleet in Being is the most well-rounded doctrine used by most navies. It has a very general purpose and enhances a number of smaller and miscellaneous stats. It also somewhat equally buffs most ship classes, except for submarines, which it does not favor at all. This doctrine basically counters Trade Interdiction and helps with escorts and surface action. This is also the best doctrine for newer players.

Despite being bested by Trade Interdiction in terms of submarines, it is still better than Base Strike. It also turns Destroyers and Light Cruisers into brawlers and effective sub-hunters. It sub-optimally buffs capital ships, mostly favoring Heavy Cruisers. It gives the most organization out of all of them, though.

Trade Interdiction

The most offensive doctrine, Trade Interdiction, lets you focus on taking out enemy logistics. It is great for a navy that is outmatched by larger enemy navies. It lets you focus on stealthy raiders and utilize both submarine and surface raiding. It also gives them an enhanced ability to seek and destroy enemy shipping and avoid detection.

The usual drawback with such a detachment is that you have lackluster anti-submarine capabilities as well as terrible escort ships. It is also usually the cheapest doctrine to go for, as you really only need smaller ships. Again, this was historically used by the Germans, so if you wish to LARP, this is your route. Als works remarkably well with minor powers.

Overall, Trade Interdiction improves both visibility and reducing detection, making your ships remarkably stealthy. This comes with the drawback of having a lower organization. It is also the only doctrine that actually boosts raiding efficiency.

Base Strike

The historical approach of the Japanese and Americans, the Base Strike Doctrine Tree, focuses on Naval Aviation, particularly boosting carriers and their screens. Additionally, it gives minor buffs to other ships like submarines and heavy cruisers. However, it gives no real buffs to large capital ships. Despite this, in most scenarios, the buffs are still the second best, as any buffs they give are still better than the ones in Trade Interdiction.

While this doctrine mainly buffs carriers for composition, it is definitely advisable to have a mix of screens, heavy cruisers, and carriers, as you'll still need to hold the enemy off until your naval aviation can hit them. Speaking of which, this doctrine requires you to have good naval aviation as well as ships, but since you can usually ignore Battleships, it is still cheaper to do this.

Base Strikes also buff port strikes and naval targeting, making it easier to blow enemy fleets out of their ports, Pearl Harbour style. That being said, this is definitely the hardest to master doctrine and is very situational.

Best Doctrine

To make a real choice or selection on which doctrine to use, you really have to realize what your game plan is. If you have a strong strike force ready and running or can get one running very quickly, then go for Fleet in Being. It is the same if you expect to deal with lots of enemy raiders, especially submarines.

If the enemy horribly outclasses you and has no real industry to support constant ship production, go for Trade Interdiction and focus on submarines. This way, you can starve them out and finish them off with your air force.

If you are using Naval Bombers and a lot of carriers and land-based naval assets, then go for Base Strike. This way, you will slowly be able to wear down the enemy navy. There is no room for error here, however, as in a straight fight with no air support, you'll quickly end up on the bottom of the sea.

Pure raw stats aside, Trade Interdiction remains the worst doctrine to pick overall, except for its bonuses to submarines. This sort of makes them into one-trick ponies, and you will need to dominate the air to keep up.

Spirits

Now, Naval Spirits are actually better to get before going to Doctrines, so keeping that in mind, the Spirits are, overall, very powerful. You get to pick between three categories with a usual option for six spirits. Additionally, each doctrine also unlocks a certain spirit in some of the categories.

Spirit of the Naval Academy

Out of the three general ones, the one boosting attack is your best friend. Every +1 means +5% damage. This starts to add up, so Instilled Aggression is your best choice. Signal Training is also a good choice for those using Base Strike.

Spirit of the Navy

In this regard, all of them are fairly good and balanced. However, out of all of them, Naval Refit Yards and Naval Reform are the best since they are very reliable and all-purpose. Meanwhile, Jeune Ecole and Flexible Contracts are better when you need a lot of screens.

Spirit of Navy Command

This one is also dependent on your exact plans. However, the three doctrine-based ones are the worst to keep since, most of the time, you will want to have a big, decisive battle. If you have a lot of big ships, Close Combat is the best option. If you have a lot of screens, go for Efficient Communications. Night Fighting and Inclement Weather Experience are situational but still useful to have around.

Night Fighting overall actually gives you some very good all-rounder boosts. Even though it only works at night, that's still half of each day. So, the 10% attack increase roughly translates to 3%. Meanwhile, the extra spotting and reduced visibility means you will escort ships better. The Inclement Weather Experience is very useful in open seas with a lot of carriers as weather very heavily affects your carriers.

Check out our Hearts of Iron IV: Götterdämmerung DLC review and other guides below:

• Hearts of Iron IV Divisions Guide
• Hearts of Iron IV Guide | Division Templates
• Hearts of Iron IV Guide | Console Commands for Modding
• Hearts of Iron IV Guide | Navy Tips and Tricks