Naval doctrine

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Naval doctrine is a technology group that allows a nation to specilize the way its navy conducts naval warfare. Three exclusive branches which provide different bonuses are available:

Fleet in Being
A strong fleet focused around battleships means that we are a force to be reckoned with when deployed at sea.
Trade Interdiction
Against a stronger naval opponent we can focus on tying up their fleet and destroying supply lines to starve their war machine.
Base Strike
With a strong focus on carriers and their support, no enemy will be outside our reach, whether on land or at sea.

Each doctrine has a base time to research of 200 days.

Some countries have enabled naval doctrines at game start 1936:

Doctrine Countries
Fleet In Being.png Fleet in Being Flag of Australia Australia, Flag of British Malaya British Malaya, Flag of British Raj British Raj, Flag of Canada Canada, Flag of China China, Flag of United Kingdom United Kingdom, Flag of France France, Flag of Italy Italy, Flag of New Zealand New Zealand, Flag of South Africa South Africa, Flag of Soviet Union Soviet Union
Trade Interdiction.png Trade Interdiction Flag of German Reich German Reich
Base Strike.png Base Strike Flag of Japan Japan, Flag of United States United States

Fleet in Being: This is the well-rounded general purpose set of naval doctrines that most substantial navies used. It enhances Search & Destroy for capital ships, submarine detection for screening ships, and bonuses for all classes, although subs seem least favored. This is the most powerful doctrine for surface action. It is the most efficient in responding to the escort needs of convoys and in anti-submarine warfare.

Trade Interdiction: This is an offensive doctrine focusing on attacking enemy convoys with coordinated stealthy surface and submarine raiders that have superior abilities to find and destroy enemy shipping while evading enemy detection. Such stealthiness can also be valuable in normal combat or escaping from it, which is usually the best course. Submarines are made very dangerous to the enemy. The trade-off under this doctrine is that light cruisers and destroyers have mediocre anti-submarine warfare capabilities and weak escort efficiency bonuses, so vulnerable friendly shipping may require more effort to defend. Germany adopted the raiding strategy in its efforts in both world wars to strangle Great Britain by cutting off its shipping, but this can also be suitable for minors seeking a naval presence to strike enemy trade with moderate risk and expense.

Base Strike: This is similar to the approach of Japan and the United States. It focuses on blue water navy carriers and their light cruiser and destroyer screens, with submarines also receiving decent bonuses for supporting carrier operations. There are no class-specific bonuses at all for battleships, battlecruisers or heavy cruisers, but if built they share the array of global bonuses under this doctrine. Having at least a few fast heavy cruisers that can keep pace with the carriers for bombardment and surface action is advisable, but it is possible to focus just on research and production of carriers, screens and carrier aircraft to make the best use of limited resources.

Naval doctrine comparison table by unit[edit]

Note: Definitions of HOI4 naval terms follow the doctrine table and charts below.

Submarine (SS) stats
Doctrine Organization Surface Detection Raiding Coordination Attack Defense
Fleet in Being +40 +50% +20%
Trade Interdiction +50 +100% +110% +10% +10%
Base Strike +40 +50% +20%
Destroyer (DD) stats
Doctrine Organization Sub Detection Escort Efficiency
Fleet in Being +60 +50% +90%
Trade Interdiction +10 +10% +10%
Base Strike +50 +40% +60%
Light Cruiser (CL) stats
Doctrine Organization Sub Detection Surface Detection Raiding Coordination Surface Visibility Escort Efficiency
Fleet in Being +10 +20% +90%
Trade Interdiction +30 +60% +100% -25% +10%
Base Strike +50 +60% +60%
Heavy Cruiser (CA) stats
Doctrine Organization Search & Destroy Surface Detection Raiding Coordination Surface Visibility Armor Attack
Fleet in Being +40 +50% +10% +10%
Trade Interdiction +40 +50% +60% +100% -25% +10%
Base Strike +10%
Battlecruiser (BC) stats
Doctrine Organization Search & Destroy Surface Detection Raiding Coordination Surface Visibility Armor Attack
Fleet in Being +40 +50% +10% +10%
Trade Interdiction +40 +50% +75% +160% -50% +10%
Base Strike +10%
Battleship (BB) stats
Doctrine Organization Search & Destroy Surface Detection Raiding Coordination Surface Visibility Armor Attack
Fleet in Being +60 +50% +10% +10%
Trade Interdiction +50 +50% +50% +90% -75% +10%
Base Strike +20 +10%
Carrier (CV) stats
Doctrine Organization Naval Air Agility* Sortie Efficiency Carrier Overcrowding Armor Attack
Fleet in Being +30 +20% +10% +10%
Trade Interdiction +60 +20% +10%
Base Strike +120 +10% +40% -50%
  • Applies only to airplanes based on carriers
Other bonuses
Doctrine Naval Targeting

Naval Bombers
Close Air Support
Tactical Bombers
Port Strikes

Naval Bombers
Close Air Support
Tactical Bombers
Naval AA Attack
(All Ships)
Fleet in Being +10%
Trade Interdiction +20%
Base Strike +40% +50%

List of all doctrines[edit]

Fleet in Being[edit]

Fleet In Being icon

Fleet In Being

  • Battleship, battlecruiser, heavy cruiser:
Ships stay in port where they are safer and only engage enemies at opportune moments. The presence of our ships will make enemies more reluctant to take our ports.
Battlefleet Concentration icon

Battlefleet Concentration

  • Battleship, battlecruiser, heavy cruiser:
Call in nearby ships as soon as an enemy vessel is spotted. Coordinated focused fire quickly render enemy ships useless. Hunt them down one by one.
Convoy Sailing icon

Convoy Sailing

Introducing compulsory convoy sailing will make it easier to spot enemy raids and respond in time. Safety in numbers is the way to go.
Submarine Operations icon

Submarine Operations

We do not need to engage the enemy fleet head on to win the war. Strike at their trade convoys before they can react and disappear below the surface again. You cannot fight what you cannot see.
Subsidiary Carrier Role icon

Subsidiary Carrier Role

Carriers support Battleships, improving their readiness in switching from defense to offense. The utility of the Carrier as both an eye in the sky and powerful quick strikeforce complement the slower Battleships well.
Convoy Escorts icon

Convoy Escorts

Fast surface ships as part of our convoys will allow us to spot enemy submarines and respond in time. Detection is they key to eliminating the submarine nuisance.
Undersea Blockade icon

Undersea Blockade

Submarines are the perfect tool for cutting of the enemy's inflow of important raw materials. We will cripple the enemy's production and win by starving them out.
Hunter Killer Groups icon

Hunter Killer Groups

  • Destroyer, light cruiser:
  • Escort efficiency: +10%
  • Destroyers form groups to hunt down enemy submarines. The combined efforts of scouting and hunting specialists make a fantastic killing team.
    Escort Carriers icon

    Escort Carriers

    The area covered by a Carrier's aircraft makes escorting trade convoys a much easier task. Securing the flow of resources is essential.
    Convoy Interdiction icon

    Convoy Interdiction

    Improved coordination of our submarines will let them strike at trade convoys en route. Disrupting the enemy's supply lines will give us the strategic advantage.
    Floating Fortress icon

    Floating Fortress

    With battleships on highest alert we will always be prepared to respond if the enemy dares threaten our waters. Any fleet needs a solid foundation and the power of the battleship is unparallelled.
    Integrated Convoy Defense icon

    Integrated Convoy Defense

    Better navy and air coordination allow us to strike at enemies from miles away before they are near our trade convoys. This will drastically increase the effectiveness of convoy sailing.
    Submarine Offensive icon

    Submarine Offensive

    Reaching the pinnacle of communication between our submarines allows them to go on the offensive. Let us destroy the enemy trade convoys faster than they can replace them.
    Floating Airfield icon

    Floating Airfield

    Improved integration of Carriers into our fleet keeps us prepared to strike from both sea and air. It is key that we dominate the air wherever we go.
    Grand Battlefleet icon

    Grand Battlefleet

    • Battleship, battlecruiser, heavy cruiser:
  • Naval AA attack: +10%
  • Capital ship attack: +10%
  • Leadership training allow our commanders to keep calm in the heat of battle even when commanding immense fleets. Our fleet will crush any opposition head on.

    Trade Interdiction[edit]

    Trade Interdiction icon

    Trade Interdiction

    • Heavy cruiser, light cruiser, submarine:
    The sooner we spot the enemy ships, the sooner we can destroy them. Hit their trade convoys and escape before they have time to react.
    Raider Patrols icon

    Raider Patrols

    • Battleship, battlecruiser, heavy cruiser, light cruiser:
    Patrols of both fast and gun heavy ships leave the enemy trade convoys nowhere to hide.
    Not only submarines can hunt.
    Carrier Operations icon

    Carrier Operations

    Carriers will allow our pilots to strike at sea faster and easier than from our airbases on land. We will strike before they have time to react.
    Convoy Interdiction icon

    Convoy Interdiction

    Improved coordination of our submarines will let them strike at trade convoys en route. Disrupting the enemy's supply lines will give us the strategic advantage.
    Capital Ship Raiders icon

    Capital Ship Raiders

    • Battleship, battlecruiser:
    With our most powerful ships on the hunt for trade convoys, the enemy will no longer find safety in numbers. They are sitting ducks praying we will not find them.
    Convoy Sailing icon

    Convoy Sailing

    Introducing compulsory convoy sailing will make it easier to spot enemy raids and respond in time. Safety in numbers is the way to go.
    Unrestricted Submarine Warfare icon

    Unrestricted Submarine Warfare

    Let our submarines sink any vessel without warning, civilian or not. While some consider this a breach of the rules of war, there is no denying its effectiveness.
    Battlefleet Concentration icon

    Battlefleet Concentration

    • Battleship, battlecruiser, heavy cruiser:
    Call in nearby ships as soon as an enemy vessel is spotted. Coordinated focused fire quickly render enemy ships useless. Hunt them down one by one.
    Subsidiary Carrier Role icon

    Subsidiary Carrier Role

    Carriers support Battleships, improving their readiness in switching from defense to offense. The utility of the Carrier as both an eye in the sky and powerful quick strikeforce complement the slower Battleships well.
    Wolfpacks icon

    Wolfpacks

    With our submarines organized into packs the coordination between them is greatly improved. Once an enemy is located our submarine lies in wait until the rest of the pack arrives. Attacking only when the odds are overwhelmingly in our favour.
    Floating Fortress icon

    Floating Fortress

    With battleships on highest alert we will always be prepared to respond if the enemy dares threaten our waters. Any fleet needs a solid foundation and the power of the battleship is unparallelled.
    Naval Air Operations icon

    Naval Air Operations

    Pilots trained to perform missions from carriers opens a new way for us to dominate the seas. Airplanes are an efficient way of thinning out the enemy fleet.
    Advanced Submarine Warfare icon

    Advanced Submarine Warfare

    A massive improvement on communication between our submarines lets them time attacks to perfection. When they finally see us it will be from a sinking ship.
    Floating Airfield icon

    Floating Airfield

    Improved integration of Carriers into our fleet keeps us prepared to strike from both sea and air. It is key that we dominate the air wherever we go.
    Combined Operations Raiding icon

    Combined Operations Raiding

    • Battlecruiser, heavy cruiser, light cruiser, submarine:
    Designating all resources to hunt for enemy trade convoys. Coordination between our main fleet and submarines makes our fleet ever alert. No ship will go unnoticed in our waters.

    Base Strike[edit]

    Base Strike icon

    Base Strike

    Striking at the enemy's ports will cripple their ability to rebuild their fleet. This will allow us to dominate the seas by sheer numbers.
    Convoy Escorts icon

    Convoy Escorts

    Fast surface ships as part of our convoys will allow us to spot enemy submarines and respond in time. Detection is they key to eliminating the submarine nuisance.
    Submarine Operations icon

    Submarine Operations

    We do not need to engage the enemy fleet head on to win the war. Strike at their trade convoys before they can react and disappear below the surface again. You cannot fight what you cannot see.
    Carrier Primacy icon

    Carrier Primacy

    Modern airplanes have greater range and precision than ordinary naval guns. Integrate carriers into our fleet and dominate the seas from the sky.
    Escort Patrols icon

    Escort Patrols

    • Light cruiser, destroyer:
  • Escort efficiency: +10%
  • Improving detection makes our convoy escorts far deadlier to submarines. With nowhere to hide they pose no real threat.
    Undersea Blockade icon

    Undersea Blockade

    Submarines are the perfect tool for cutting of the enemy's inflow of important raw materials. We will cripple the enemy's production and win by starving them out.
    Carrier Task Forces icon

    Carrier Task Forces

    • Carrier, light cruiser:
  • Naval targeting: +10%
  • Organized task forces with carriers and light cruisers ensures that the enemy will never catch us off guard.
    Convoy Sailing icon

    Convoy Sailing

    Introducing compulsory convoy sailing will make it easier to spot enemy raids and respond in time. Safety in numbers is the way to go.
    Convoy Interdiction icon

    Convoy Interdiction

    Improved coordination of our submarines will let them strike at trade convoys en route. Disrupting the enemy's supply lines will give us the strategic advantage.
    Floating Airfield icon

    Floating Airfield

    Improved integration of Carriers into our fleet keeps us prepared to strike from both sea and air. It is key that we dominate the air wherever we go.
    Integrated Convoy Defense icon

    Integrated Convoy Defense

    Better navy and air coordination allow us to strike at enemies from miles away before they are near our trade convoys. This will drastically increase the effectiveness of convoy sailing.
    Submarine Offensive icon

    Submarine Offensive

    Reaching the pinnacle of communication between our submarines allows them to go on the offensive. Let us destroy the enemy trade convoys faster than they can replace them.
    Massed Strikes icon

    Massed Strikes

    Pilots trained for carrier missions will allow even an overcrowded carrier to function smoothly, swarming the enemy and vastly improving their effectiveness in naval battles. A carrier needs to run like a well oiled machine where everyone knows their role.
    Floating Fortress icon

    Floating Fortress

    With battleships on highest alert we will always be prepared to respond if the enemy dares threaten our waters. Any fleet needs a solid foundation and the power of the battleship is unparallelled.
    Carrier Battlegroups icon

    Carrier Battlegroups

    • Carrier, light cruiser:
  • Naval air agility from carriers: +10%
  • Carriers are able to strike at the enemy from a greater distance than any naval cannon and with eyes in the sky we will never be caught off guard. Carriers in mass is a force to be reckoned with.

    Definitions and significance of naval doctrine terminology[edit]

    • Search & destroy: The higher the search and destroy rating, the faster allied ships will become involved in the fight. Naval engagements normally start off with just a few combatants involved. As the naval engagement continues, more and more ships from the sea zone are involved. A higher search and destroy rating speeds up the rate that friendly ships join the fight. This helps a country win the "firstest with the mostest" race.
    • Surface detection: Increases a ship's ability to detect enemy surface ships.
    • Surface visibility: This is the "hide in shadows" score. The more visible a friendly surface ship is, the more likely an enemy will spot it and subsequently attack the friendly ship. The smaller the visibility, the better. The enemy can't destroy a fleet it can't see. For example, a Japanese fleet with minimal surface visibility score can sneak its surface fleet past Singapore in the Straits of Malacca.
    • Organization: The higher the organization rating of a ship, the longer it can stay in a fight.
    • Submarine detection: This increases a ship's ability to detect enemy submarines. A fleet can only engage submarines if it knows they're there.
    • Raiding coordination: This describes the number of submarines that are involved in a convoy raid. The higher the raiding coordination value, the more submarines are involved in convoy raids.
    • Escort Efficiency: This counters an enemy's raiding coordination. The higher the escort efficiency, the more screening ships (destroyers and light cruisers, not battleships and cruisers) are involved in protecting convoys. An increased escort efficiency score helps prevent troop transports being sunk.
    • Sortie efficiency: Sorties are air missions launched from an aircraft carrier.
    • Capital ship armor: More armor decreases the amount of damage taken by the big ships.
    • Naval targeting: The higher the naval targeting number, the more likely a surface or carrier naval bomber is to hit an enemy ship (this might be wrong, please edit).
    • Naval AA (Anti-Air) attack: This value adds a positive modifier to the "to hit" dice of friendly ships' attacks against air units. The higher the number, the better, to protect against both land based and carrier based air attacks. The naval AA attack value protects against port strike attacks.
    • Capital ship attack) This value adds a positive modifier to the "to hit" dice of a large friendly ship. The higher the number, the better.
    • Carrier overcrowding: This doctrine reduces the penalty for crowding too many planes on an aircraft carrier. Its significance is that it allows carriers to bring more aircraft to a fight. More is better.
    • Sortie efficiency: The higher the sortie efficiency rating, the more aircraft carrier (not land based) aircraft will be involved in a fight.
    • Port strike: A port strike is an air attack against enemy ships located in a port. The number of airplanes involved in a port strike is increased by the port strike value (e.g. 50% more aircraft are involved in a port strike if you have the first "Base Strike" naval doctrine).