AA: Anti-Air
BB: Battleship
BC: BattleCruiser
CA: heavy cruiser
CL: Light Cruiser
CV: aircraft carrier
DC: Depth Charges
DD: Destroyer
NAV: naval bombers
SS/SB/SUB: submarine
SHBB: SuperHeavy Battleship

Part intended for players who don't know anything at all about naval gameplay, step by step.

You research a hull design in the research tab.

You then go to the military production tab. There you click to produce a new ship. The option to modify the design of a ship is next to the ship. Click on it. You need naval xp for every module you add/remove/modify. You gain naval xp by exercising your fleet or fighting. If there is already a ship of this class in production or produced, saving the change will create a new variant.

To refit a ship to a new variant, click on the task force in which it is, then click on the ship, then click on the upwards yellow arrow. If it's greyed, that means that there is no upgrade available. It will go to a shipyard for refitting.

By default, newly produced ships join the reserve task force. You can tell it to join a particular task force in the production queue.

Ships are always assigned to a task force. Delete a task force and it will delete the ships aswell. Merging or splitting do not delete ships. You assign missions to individual task forces. You can create templates of task forces so that they automatically get reinforced from the reserve fleet if they are lacking a ship (sunk or just missing).

Task forces are regrouped into fleets. You can put an admiral at the head of the fleet. Naval areas are assigned to the whole fleet. So you can have 10 task forces assigned to the same naval areas performing 10 different missions. The level of risks the ships will take is set at the fleet level.

When there are enemy ships in the same area, spotting tests are run. If the spotting fleet is confident enough (according to the risk level set), it will engage in a naval battle.

Naval battles are separated into 4 areas for each side. The one at the bottom is the submarine. Submarines are either detected or undetected. They fire torpedoes and can only be damaged by Depths Charges.

The one the closest to the middle is the screening area. CLs and DDs are assigned to this area. They take no damage from torpedoes and protect the other ships from the torpedoes. They are the primary target of light attack, and the secondary target of heavy attack and airplanes attack. They are very vulnerable to heavy attack.

The area next to the screening area is the heavy ships area. SHBBs, BBs, BCs and CAs go there. They are the primary target of heavy attack and airplanes attack. They are very vulnerable to torpedoes. As you guessed it, you need screening ships to protect the heavy ships from torpedoes, and you need capital ships to protect the screening ships from enemy heavy attack.

The last area is the CVs area. It's also the convoy area. They are the secondary target of the torpedoes and the last target of everything else.

Tell me if there is something missing, but I think I have explained all the basics.

This is an explanation of all the mechanics and meta I have understood so far, and the navy I am using and its ships designs. It's only for SP, but a lot of things also work for MP. It will be divided into different chapters for a clearer explanation and understanding.

Too many times, when we get into something new, we go too far and fail to see the bigger picture and why some things we did weren't worth it or out of the scope. This is the case of a lot of naval guides that often say to "just" build 4 BBs, 4 CVS, 16 CLs and 50 DDs, which is only doable if you are the US or you have already won the playthrough. This guide focuses first on why you need a naval strategy and then logically builds up a generic strategy that you are free to modify.

There are 2 reasons why you need a naval strategy during your playthrough, which will be the 2 main parts of this guide:

- you and your enemy use convoys for several reasons (bring ressources to your industry, transport troops and resupplying them). Sinking most enemy convoys in an area will give you a noticeable advantage on the ground on some parts of the world (Pacific, Indian Ocean, Oceania) aswell as inflict huge casualties and harshly damage the industry of your enemy. It's 75% of why you should engage in a naval strategy, to protect yourself and have an advantage on your enemy.

- naval invasions require naval supremacy and naval bombardment are valuable tools.

Now is time to set up a context:

- naval strategy is built strategy, during a playthrough, for a long time most of your ships will be your starting ships, so you must start with the idea of a flexible management, not with the image of a perfect fleet that you will build and then use. You will use what you already have and then slowly replace your fleet with better ships.

- fuel is limited, you want to use as little ships as possible on a mission, so you want your ships to be as efficient as possible.

- the naval system relies on missions that you give to task forces, regrouped into fleet. Minesweeping ships on minelaying missions won't sweep mines. Because of that, it's better to have specialized ships based on the missions

Now that we have the context and know why we are going into a naval strategy, we can start looking into the naval missions, which will be the subject of the next 2 parts.

Spotting is everywhere in the naval gameplay, so it's important to understand the big rules and how to make it go your way.

Spotting is a tug of war between 2 task forces. The one with the highest spotting goes closer to spotting the enemy. The larger the difference, the faster the spotting. That means that you need spotting to hide yourself from the enemy task forces aswell.

I am not going to steal the good job of someone else so here is another source to go more in the details: https://forum.paradoxplaza.com/forum/index.php?threads/naval-detection-guide.1157358/#post-25225470

So the big rules are:

- better ships with higher detection is the most important thing, a high speed is important

- more of those ships is better

- air supremacy helps a lot

- radars and good old decryption

Heavy fighters are not only more efficient for air supremacy, they also are a better choice than CVs because they require less research (you have to research the hull, then the design, then the CV fighters), less expensive in production, take less time to build, use less fuel and can be reused for inland battles.

So to support your fleet, the best is to have radars on your coasts and heavy fighters. Tactical bombers are also a very useful tool to support naval invasions, do port strikes and naval strikes. If there is no enemy airforce, focus on tactical bombers.

Best patrol ship is either a submarine with radar or a CL full of plane launchers (called Patrol CLs in this guide).

When you import ressources, they go either through land (and those ones can't be raided) or through naval convoys. The longer the naval route, the more convoys are required. So it's better to deal with nations as close as possible to minimize the number of escorts needed.

All convoys, either troop transports or ressource transports, can be told to avoid some naval areas. For that, click on the naval area, and you will have 3 access options at the bottom right. It's either let them go free, tell them to avoid the area, or ban them from going through this area. The more you restrict areas, the longer the naval routes, the more convoys are needed, the more escort ships are needed. So be spare.

Convoys have very little AA, gunnery, are the slowest ships in the game, can't be upgraded and don't have stats that allow them to hide. If someone is looking for them, they are going to be spotted and attacked.

Convoy escort mission

You can assign as many areas to a task force with this mission as you want without losing any efficiency.

Escort efficiency is lost when there is less than 1 screening ship for every 2 convoy.

To count the number of convoys escorted by a fleet, you sum all the convoys used used by all the trade routes that go through the area covered by the fleet. This means that it requires as many escort ships to cover 1 naval area from a trade route than to cover the entire route. But the escort ships will only protect them in the assigned areas. The only way to increase the number of convoy ships to be escorted is to increase the number of escorted naval routes by adding more naval areas to the fleet.

So it's better to have a single fleet with all your escort ships inside, assigned to the entire world. If you split into 2 fleets, each fleet will have its own, lower, efficiency. You divide this fleet into 10 task forces so that they can engage into up to 10 naval battles (instead of 1 and having convoys being sunk into 9 other battles).

Escort efficiency is gained through naval doctrines and an experienced admiral with higher coordination, allowing you to need less than 1 screening ship for every 2 convoys.

Since submarines are the go-to raiding ship, the best ship is the cheapest ship which can make a sub flee. It needs to be as cheap as possible so that you can produce as many of them as possible. And that's a tier 1 DD, with a tier 1 engine, and a tier 1 gun. It already has Depth Charges (DC) value of 1 so the submarines will flee.

With the default values, you need to put 3 dockyards on DD production for every dockyard on convoy production. This is lowered with higher escort efficiency (because you need less ships). With the right doctrines, you will only need 1 DD for 3 convoys, which means 2 dockyards on DD production for every dockyard on convoy production.

If you are being raided with surface ships such as light cruisers, nothing stops you from adding capital ships such as CAs in your task forces. Just keep an eye on your fuel.

Convoy raiding mission

By default, you can give around 1 area to raid per task force before losing efficiency. The more areas, the less raiding efficiency. The right doctrine and an admiral with higher coordination will increase raiding efficiency, allowing you to raid the same amount of areas with less task forces (and regroup them).

Convoys are on their own until the battle start, so spotting them isn't a problem. A higher detection will speed up things, and hide you better, but that's not a necessity.

The basic strategy is simply to send task forces of submarines to sink convoys. More torpedoes is a more efficient attack before the escort shows up. A radar on your submarine make it harder to be spotted and easier to find convoys. So the best submarine would be as many of the best torpedo tubes as possible and a radar.

This strategy is enough against AI. However, if the enemy has 100% escort efficiency, you can have 10 000 submarines, it will change nothing (unless you spam attacks so much that all enemy escort task forces are tied up) because escort efficiency depends on the number of convoys, not on the number of attackers. That's why I prefer to have a token force of submarines of less than 100.

Your next best bet would be light cruisers, and then go higher and higher. BBs might not be worth it on raiding missions. The Trade interdiction doctrine makes surface ships good raiding vessels, but we will see about that later in the doctrine part. The best light cruiser for this would be a Patrol CL: light cruiser with as many plane launcher as possible + AA. Give your raiding vessels as much detection as possible to make them harder to find.

For you fleet organization, you can either have a single admiral with as high raiding efficiency as possible to concentrate your firepower into fewer task forces (better for surface ships), or make as many task forces as possible to overwhelm the escort task forces (better for submarines).

A human player needs naval supremacy on all naval areas on the way of a naval invasion to trigger it.

This value is again a tug of war between you and your enemy. The primary value is the number of ships operating in the area. Even if they are at port, strike forces count towards naval supremacy. There are then 2 very important modifiers: the number of friendly aircraftand the number of friendly mines in the naval area. They make your ships count more towards naval supremacy.

Strike forces wait in a port for an enemy fleet to be spotted. So let's start with patrol missions first.

Patrol

A task force can only patrol one naval area at a time. So you need as many or more patrol task forces than the number of naval areas covered by your fleet.

Spotting has already been covered in a previous chapter.

Patrol CLs (as many airplane launchers as possible) have my preference, but submarines also make great spotting ships.

A strike force without efficient patrols is blind, and thus useless. So it's very important to produce good patrol ships.

Strike forces

When a task force is given the Strike force mission, it goes into a nearby port and waits there. You can give it as many naval areas to cover as you want as long as it's in range of the port where the task force waits. There is no efficiency, just it's in range or not.

Then when a battle happens or an enemy task force is spotted, it will move out and join the battle. You need a fast task force, close to where you think the fight will be. Otherwise they might not have time to join the battle before it's over (even if they reach the battle, they still need to wait to join the battle itself).

To build your strike force is going to require a lot of explanation. So here it is.

The positioning meta

Positioning is a value your fleet has during a battle. If it reaches 0%, your fleet is half as powerful as it could be.

The first way to reduce enemy positioning is by having less ships than him. It works by increment of 25%, twice. If you have 10 ships and the enemy 15, he has 0% malus. If the enemy has 20 ships, he has -25% positioning. At 30+, he has -50%. So, in theory, you want a fleet as small as possible.

The second way is that every ship that joins the battle after the start reduces your fleet positioning by 5%, for a maximum of 50%. So you want as many of your ships in the first contact as possible. So you want as few ships as possible while as many enemy ships as possible.

Spotting the enemy fleet gives you a positioning advantage proportional to your spotting advantage on the enemy. Which means that you want all your patrolling ships to have as much spotting as possible and the lowest visibility possible. In general, your spotting abilities are compared to the enemy's one, and this determines who gets to spot whom and at which speed. The best spotting ship is a CL with as many patrol aircraft as possible.

An admiral trait also gives +25% positioning and a storm gives -10% positioning.

Overall, you want as few ships as possible. Which means that you want heavier and better ships.

The AA meta

Afaik, carriers are pretty useless atm and I haven't looked into them so far, but planes can still damage your ship and it's important to have AA anyways.

Read this post: https://old.reddit.com/r/hoi4/comments/awfpn7/naval_aa_effect_on_incoming_air_damage/

The general idea is that AA becomes less and less efficient as you have more AA. Because of that I always have at least a tiers 1 AA on my ships on the dedicated slot so that if they are attacked by air while alone, they still have a cost efficient AA.

Airplanes attack capital ships first, so put as many AA as possible on the capital ships.

Dedicated AA CLs are a marginally (0-10%) better way to provide AA cover to your screening ships if they aren't accompanied by a capital ship. Second best is to have 2 AA guns on each ship (1 in the dedicated slot, 1 in the optional).

The armor meta

I have received a lot of contradicting information and my last guide on Reddit was most probably very wrong, so I won't get into the details on how damage is calculated. Still there are important rules that are 100% sure.

Unarmored ships suck in naval battles. DDs die like flies. When you put DD in your Strike force, you can expect 80% of them to sink in the first serious naval battle. it's a waste of ressources and it won't win you the war on the long run. Use CLs with as much armor as possible as screening ships. You can repair them for cheap. You have to rebuild DDs.

Heavy cruisers are capital ships that get pierced by all other capital ships, including Heavy cruisers. Whatever the way damage is calculated, it's bad. Don't use CAs in strike forces. They are going to get murdered the same way DDs are.

I will update this part when I have more information.

Strike force design

You want between 4 and 8 screening ships for each capital ship. Otherwise torpedoes will hit your capital ships. You need 1 heavy ship to screen 1 CV. CVs count as capital ships.

A last note: CVs seem very underpowered during naval battles, not justifying their cost and the screening ships they require (it's a capital ship), especially if you already have heavy fighters covering the area where your task force is operating.

2 BBs: 2 turrets + secondary batteries for the remaining slots + radar + fire control + armor + 2 AA

8 Battle CLs: 1 tier 1 DC + 2 best CL light batteries + 1 torpedo + radar + sonar + armor

This strike force is small compared to what other people propose, it's to keep the price and build time low (especially the CLs that I have found costy, and that's why I am not using all the slots, so that I reliably have enough CLs to screen the BBs) so that you can reliably build it during a playthrough. It won't win against a death ball but it will survive and deal huge damage, giving you a small strategic advantage. Don't hesitate to scale it up if you have the ressources and the fuel.

Naval invasion support

It works like Strike forces for the efficiency.

Ships on this mission will escort troop convoys and give shore bombardment debuff to enemies in the area.

Shore bombardment is 10% of heavy attack and 5% of light attack, so any fleet with guns and some Deptch Charges will do. It's just easier for a strike force to do it (because the naval invasion would have required naval supremacy, for which you would have used your strike force, so it will be still around).

Mines increase the risks of accidents, reduce naval invasion, increase naval supremacy of an area and reduce naval speed by a lot (which has a ton of consequences). It's a very defensive tool to take control of an area.

Minelaying

Minelaying missions do not lose efficiency when adding more areas to cover to a task force. It only gives it more work.

Minelaying is the perfect support mission for your fleet. It will help build up naval supremacy of an area for a strike force fleet. It will make life easier for your raiding task forces. It will sink enemy raiding subs for your escort fleet. It will help defending against naval invasions. You name it.

I find it simpler to manage to have all the minelaying ships in the same fleet, distributed into 10 task forces. As soon as they can't put mines anymore, add more naval areas to mine.

Best minelayer is the submarine with radar and minelaying tubes, period. It also gets a bonus of 20% later in the tech tree.

Minesweeping

It works the same way than minelaying, except that only DDs can do it.

Use them the same way than minelaying task forces.

DDs can equip up to 3 minesweeping gear. Unless there is another threat to deal in the area, DDs with as many minesweeping gear as possible are the best tool to remove mines. Old designs never go obsolete. AI doesn't use minelaying enough to be a threat. You don't need them in SP.

For mine warfare with air power, it uses more oil than ships per minelaying/minesweeping and older designs are as good as newer designs, so use your old designs.

Production

You can put up to 15 dockyards per line of production for convoys.
You can put up to 10 dockyards per line of production for light ships (subs, DDs, CLs).
You can put up to 5 dockyards per line of production for heavy ships (CAs, BC, BBs, SHBBs, CVs).

Capital ships require chromium except heavy cruisers (which are useless as capital ships).

Don't forget to increase the number of dockyards to repairs in the production screen !

Tiers

Those are roughly true:

1922/early/tier 1: the worst, worst slots, not that cost efficient, little fuel consumption, however its components have the smallest debuffs (fire control, AA, heavy battery, medium batteries are interesting) but also the smallest buffs

1936/tier 2: where the real deal starts, decent slots availability

1940/tier 3: the cost efficient tier, all hulls except DD have all slots unlocked, still only require steel for the many part, in line with tiers 2

1944/tier 4: the rich kid yacht tier, DD and sub hulls start to require chromium, overall requires the most chromium, has the highest buffs and debuffs, think twice before using this tier of components

Research

Train your fleet all the time to convert your exceeding fuel into naval XP.

Use your naval XP for your designs and boost the research of your doctrine. Use the spare naval XP to boost the research of smaller techs (such as ammo).

Note: you don't need to research more than tier 1 DD and tier 1 Depth Charges with the strategy presented in this guide. Submarines aren't really necessary to upgrade either.

Refitting

Ships can be refitted to a variant of the same hull, or to converted CVs for cruisers and heavy hulls.

There is a cost to remove a part and a cost to add a part when they aren't of the same type, so it's very expensive. Upgrading is much cheaper but still costs a bit of production. Upgrading the armor or the engine is still very expensive.

To refit a ship, select it in the task force, then a button in the task force bar with a yellow upper arrow will be unlocked. That's it.

Because it takes a long time to build a capital ship, a good strategy for capital ships is to first build a base hull with only the mandatory slots. Then once the ship is finished to refit the optional slots with the latest technology available.

Let's look at each doctrine. And see what is the best for you. From the one I think is the weakest to the strongest. Note: they all give +10% armor.

Base Strike

The base strike bonus gives a +50% Base Strike buff. It's a strong air mission, very cost efficient when it can be used. The doctrine make it even more powerful.

The submarine tree is a standard submarine tree for convoy raiding, not very powerful.

The convoy escort gives +30% escort efficiency, which is pretty good because it lowers the number of escort ships required, and +20% sub detection for DDs. Good enough.

The main tree is mostly for CVs.

Conclusion: CVs are underpowered in this 1.6.1 update. They are less cost efficient than heavy fighters and not very good during battles. If I am already advising you to not build CVs, why would I be telling you to take this doctrine ?

Trade Interdiction

The starting tech is meh. +5% detection and +10 org to a few ships.

The escort tree has been cannibalized to buff CVs. Gives a nice +20% naval targeting for CVs. Same remark than for the base strike doctrine.

Very strong submarine tree, the best one for an overall total of +55% detection and +50% raiding. However, again, if your enemy has all its convoys escorted, the subs will be useless. Which never happens against AI. Good thing there is a third tree.

The third tree turns light cruisers and up into legitimate raiding vessels. They can sink the DDs that escort the convoys, allowing subs to sink the convoys later because of a lower escort efficiency. The doctrine gives them +50% raiding efficiency, +25% detection and between -10% and -25% visibility. The bigger the hull, the bigger the visibility buff.

Conclusion: only for countries that do not care about naval invasions and don't rely on naval trade routes. You can still escort your trade routes, but you will be less efficient. And you will have a disadvantage at sea.

Fleet in being

Starting tech has some org and a +10% minelaying efficiency. There is a second +10% minelaying efficiency later.

The submarine tree is the same than base strike, so pretty meh.

The escort tree is the strongest escort tree with an overall total of +40% escort efficiency and +25% sub detection for DDs.

The third tree and later tech gives +10% capital attack, +10% AA, more org for your capital ships and a better strike force mission (less loss of org).

Conclusion: the best tree for a generic, general naval strategy because escort, minelaying and decisive battles.

To get fuel, things are pretty simple:

Iif you have a lot of Oil, stop right there: just research the tech tree below the Silo in the Industry tab to increase fuel per Oil. You can also build infrastructure on your Oil-rich areas.

If you don't have Oil in meaningful numbers: import what you need to keep your navy doing its basic tasks. The refineries are only cost-efficient if you also need rubber, so only build them if you can't import oil or if you also need rubber. You can also in addition research the tech tree below the Silo, but it's way less efficient.

Your airforce and army usually don't use a lot of fuel, unless heavy mechanization and a lot of planes. Fighting defensively uses less fuel.

Keep your capital ships in ports as much as possible and only use screen ships on the seas to minimize fuel consumption.

Ships on hold don't use fuel. So CVs used as static air bases do not use fuel.

Fleet in being doctrine, 10 dockyards on repair duty

For naval production

Step 1: build enough base early DDs to escort all your convoys

Step 2: build 50 raiding submarines.

Optional: build minelaying subs and/or minesweeping DDs

Step 3: build CLs more and more (patrol and battle, AA if you want to bother).

Step 4: if you have the ressources, plan in advance for a number of BBs and start building them as soon as you have the right tech.

For military production

Build Heavy fighters

Build Tactical Bombers

For civilian production

Build air bases and radar on your coasts

Improve infrastructure on your oil-rich areas or import oil and build refineries

Fleet organization

It's a template in a perfect world where everything is used. Modify it as you wish

A strike force fleet: 1 strike force (2BBs, 8 CLs), 9 patrols (1 patrol CL each)

Your only escort fleet: all your escort DDs, 10 escort task forces

A raiding fleet: 1 surface raiding task force, 9 submarine raiding

Your only minelaying fleet: 10 minelaying task forces (so that they don't get all sunk at once)

Your only minesweeping fleet: 10 minesweeping task forces