Ship

Hearts of Iron IV

Naval warfare

Navy

Ship

Naval missions

Naval battle

Naval technology

Naval doctrine

A ship refers both to a piece of equipment produced by dockyards and, once launched and manned, a member of a task force ready to participate in naval warfare.

Hull types

See also: Naval technology

Hulls are the foundational component of ships, and are unlocked through research. Each hull type contains a number of module slots. These slots can be populated by modules via the Ship Designer in order to form complete ship designs (a.k.a. variants) that can be produced by dockyards.

At the start of the game, each country will have a selection of pre-existing ship variants available for production, based upon hull types which have already been researched.

Some hull types may serve as the foundation for more than one ship type, depending upon the modules that are fitted during the design of a given ship variant. For example, cruiser hulls can serve as the basis for light cruisers or heavy cruisers depending upon the type of guns that are fitted.

Hull types and their corresponding ship type(s) are listed below:

Hull type	Ship type(s)
Destroyer hull	Destroyer
Cruiser hull	Light cruiser Heavy cruiser
Heavy ship hull	Battlecruiser Battleship
Super heavy battleship hull	Super heavy battleship
Carrier hull	Carrier
Submarine hull	Submarine

Ship types

Surface warships are categorised either as capital ships or screen ships, while submarines and convoys have their own unique mechanics.

Capital ships

As the main surface combatants, capital ships are designed to sink enemy ships in surface battles.

Capital ship production time

• Super heavy battleship (SHBB): SHBBs are particularly powerful and heavily-armored battleships, based upon a dedicated SHBB hull. Unlike other hulls which receive new iterations over the years, there is only one SHBB hull in the tech tree. SHBBs are powerful enough to remain a potent threat throughout the game despite the lack of hull iterations. However, they are also prohibitively expensive and take a very long time to build.
• Battleship (BB): With their heavy armor, battleships are capable of surviving substantial amounts of incoming fire from the enemy battle line. They can also deal considerable damage of their own. Battleships are expensive and take some time to build.
• Battlecruiser (BC): Battlecruisers share the same hull as battleships, but are distinguished by somewhat lighter armor and a lower construction cost. Although they can withstand less damage than a battleship, their lighter weight also makes them faster and harder to hit.
• Heavy cruiser (CA): Heavy cruisers share the same hull as light cruisers, and are distinguished by their heavier guns. With the lightest armor of any capital ship, heavy cruisers have low survivability against battlecruisers and battleships.
• Carrier (CV): Carriers are expensive to build, and are populated by specialised aircraft which must be built separately as well. The combined fuel cost of a carrier and its air wings can be considerable. Once these hurdles have been surmounted, carrier air wings can vie for control of the air and deal bomb damage to enemy ships during naval battle. Outside of naval battle, carriers may also be used as mobile air bases.

Screen ships

Screen ships are named for their ability to protect capital ships and convoys from torpedoes during naval battles.

• Light cruiser (CL): Tougher and more expensive than destroyers, light cruisers are highly versatile and can be outfitted for a range of roles. When equipped with airplane catapults, they can serve as excellent scouts. When dedicated to firepower, they excel at destroying other screens.
• Destroyer (DD): As the lightest screen ships, the strength of destroyers lies in their numbers. During battle, they can form the bulk of a screening line to protect capital ships from torpedoes. Destroyers are also ideally suited to convoy escort missions. Both of these roles call for a sufficient quantity of ships, and destroyers are the most economical vessel to produce in the numbers required. They also boast relatively low fuel requirements. Beyond their basic armament, they can be outfitted with additional guns to increase their effectiveness against other screen ships, or torpedoes to threaten capital ships.

Submarines

• Submarine (SS): Cheap, slow, and stealthy, submarines are frequently used as convoy raiders and minelayers. During naval battle, submarines may be hidden under certain circumstances, which protects them from attack.

Convoys

Convoys are ships which carry land units, resources, reinforcements, and lend-lease equipment across water. They are treated more abstractly than all other ship types, with a variety of unique mechanics.

Convoys are distinguished by the following characteristics:

• Convoys are mostly unarmed, except for 0.2 Light Gun with Piercing 1 and 0.1 Anti-Air.
• The positions of convoys are not shown on the map, regardless of map mode. (Convoy routes can be seen on the strategic navy map mode.) Convoys are only ever directly seen during naval battles, e.g. when a convoy raiding task force automatically interdicts some convoys.
• Damaged convoys do not need to return to dockyards in order to be repaired. Any convoy that is damaged (but not destroyed) during battle will be immediately restored to perfect condition after the battle has ended.
• Convoys that are not currently in use are kept in an abstract reserve, and have no tangible presence in the game world.
• Convoys cannot be directly controlled by the player. However, it is possible to influence convoy routes by setting access levels for specific regions.
• The concepts of hulls and modules do not apply to convoys. Instead, there is only one standard convoy model. There are no technologies available to unlock more advanced convoy models.
• It is not possible to create convoy variants.
• Convoys cannot be named.

Convoys are defenseless against enemy warships, but can be escorted by friendly warships for protection.

Floating harbors

Requires No Step Back DLC

Floating harbors (sometimes called Mulberry harbors) are “ships” that can act as a temporary supply hub for naval invasion purposes. If you own at least one, then you will have access to a unique naval invasion order where they will be automatically used upon landing on an enemy shore. They create a fully stocked supply hub at the location of the naval invasion, but they only last for a while before disappearing, depending on different factors. Researching the naval transport technology Landing Craft enables the production of floating harbors. At least one dockyard is required to produce a floating harbor at a production cost of 400 IC and resource cost of 1 steel.

Access level

Main article: Strategic region#Naval access level

For any strategic region containing sea provinces, an access level can be set to determine whether ships can enter the region.

Ship details

Left clicking on a ship silhouette in the fleet will bring up its ship details. From here its statistical values are visible, along with any combat history on the second tab. It is possible to rename the ship by pressing its name. Carriers will show the attached air wings. Reorganizing air wings is done through the air wing management system. To scrap/disband a ship press the red trash bin in the upper right corner of the ship detail screen, this will return its manpower to the pool and is an alternative to sending old ships off on suicidal missions.

Carrier air wings

When building a carrier, the player has the option to pre-define how its air wings should be organized. Only carrier (navalized) aircraft may be based on carriers, and must be researched and produced separately from their ground based counterparts. The air wings of existing carriers can be adjusted by selecting the air wing in the air force overview or by selecting an air region in the air map mode, which brings up a list of all bases, and then selecting the fleet the carrier is a part of to bring up the air base windows for all carriers in that fleet. From the (carrier) base window the process is identical to establishing or modifying a wing stationed at an air base.

Viewing combat statistics

Fleet information, history and details

Hearts of Iron IV tracks experience, skill and history for individual ships, and this can be seen in the Fleet View. Select the fleet which the player wants to review. You will notice that each individual ship in your fleet is listed with a green organization and a brown strength bar, a silhouette for the ship class, a rank icon to show the ship's experience level, a vertical progress bar showing how much experience that ship has accumulated towards the next rank and the name of the ship. If the ship has participated in combat and sunk any enemy vessels, an additional icon appears next to the ship name for history. Holding the mouse over this history icon will give you a summary of how many ships the player has sunk with this vessel. Clicking on the history icon will open the ship details pop up displaying the history of ships sunk for that particular vessel.

Statistics

Each class of ship has a number of values referred to as stats. These are described below. Most of these stats can be improved by building a variant. However, be aware that increasing one stat will adversely affect a different stat. Reference Variant and Variant Upgrading and Variant Naval. Researching Naval doctrine can also increase stats.

Base stats

• Maximum speed. Maximum speed represents a value that indicates how quickly a naval vessel can move under optimal conditions. A faster ship has an easier time of disengaging from pursuers. It is also less likely to be hit by enemy fire, can pursue contacts easier when spotting the enemy, and moves faster outside of battle.
• Maximum range. A ship's range represents its onboard stores of fuel and foodstuffs, which will limit how far it can travel from the nearest friendly Naval Base.
• Organization. Organization is an indicator of a ship's combat readiness. The higher the organization rating of a ship, the longer it can stay in a fight. A ship with low or no organization cannot fight or move effectively. Reference Defines NNavy COMBAT_LOW_ORG_HIT_CHANCE_PENALTY.
• Deck size. Deck size is a measurement of how many planes a carrier can fit on board. The act of exceeding a carrier's deck size (plane limit) is known as carrier overcrowding and it results in a penalty to carrier plane missions. The overcrowding penalty is double the percentage by which planes exceed deck size. For example, a carrier with a deck size of 45 is limited to a maximum of 45 planes before triggering the overcrowding penalty. Each plane exceeding 45 adds a mission penalty of approximately -4.4% per plane. If the total number of planes on this carrier was 55, then the 10 extra planes would result in a mission penalty of -44%. The Massed Strikes naval doctrine (reference Naval doctrine Massed Strikes) reduces the penalty for crowding too many planes on an aircraft carrier by -20%. In the example above, the Massed Strikes naval doctrine would have reduced the overcrowding mission penalty from approximately -4.4% to -3.52% per plane or from -44% to -35.2% for 10 planes. Even with massed strikes however, exceeding deck size is a net loss.
• HP. HP is an abbreviation for "hit points" and is the ability to absorb damage. It represents strength which is how much damage a ship can sustain before being destroyed.
• Reliability. Reliability is the ability of a ship to continue functioning during combat. The lower the value the more likely the ship is of suffering a critical hit. Ships may receive critical hits that are much stronger than usual hits primarily because of exploding ammo or fuel tanks. Increasing a ship's reliability will reduce the chance that a received hit becomes critical. Note that the highest critical chance is done by torpedoes and not by a ship's main guns. Reference attrition and accidents.
• Supply use. How much supply the unit consumes per day. Please read Supply on the significance of this.

Combat stats

• Light Attack. Damage done by light guns. Light guns are better at targeting smaller ships.
• Light Piercing. Armor piercing of light guns.
• Heavy Attack. Damage done by the heavy guns. Heavy guns are better at targeting bigger ships.
• Heavy Piercing. Armor piercing of heavy guns.
• Torpedo attack. Torpedo attack is a value that represents a vessel's capability to damage enemy ships via torpedoes.
• Depth charges. Depth charges are a value that represents a ship's capability to damage enemy submarines via depth charges.
• Armor. Armor is a value that represents a ship's steel decking thickness, belt thickness, bulkheads, etc. The purpose of armor is to help protect a ship from attack. See Naval_battle#Armor_piercing.
• Anti-air. Anti-air, also known as Naval AA attack, is a value that represents how much firepower that a ship's anti-air guns can provide in shooting down enemy planes. 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 also protects against port strike attacks. Researching the Grand Battlefleet Naval doctrine increases all of your ships' anti-air values by +10%.

Misc. stats

• Fuel Usage. How much fuel a unit uses while it is operating. Sea units will consume fuel while on active missions or during training. Ship's effective fuel use per day is 2.4 times the nominal fuel usage shown in the ship's stats.
• Surface visibility. Surface visibility is a value that represents a ship's profile. This value is the "hide in shadows" score. The higher the value, the more visible a surface ship becomes making it more likely to be spotted and attacked. The smaller the value, the less visible the ship becomes making it harder to spot. 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. Surface visibility can be reduced (-10%) by hiring a raiding fleet naval design company such as Germany's Blohm & Voss or by researching the proper naval doctrine.
• Surface detection. Surface detection is a ship's ability to detect enemy vessels navigating on top of the sea (not under the sea such as submarines). A fleet can only engage ships if it knows they're there. A ship starts out hidden and has a chance to be spotted if it gets too close to an enemy ship (ships may also be spotted by aircraft). Reference Naval warfare Detection. Surface detection may be increased by the following means:

1. Adding more ships to a fleet or sea region
2. Adding more planes to a sea region (gaining Air Superiority)
3. Increasing radar in a sea region
4. Having better decryption than an enemy vessel's encryption (+20% improved detection for every level that your decryption is better than the enemy's encryption, reference Defines NNavy DECRYPTION_SPOTTING_BONUS = 0.2)
5. Researching higher level ships
6. Researching naval doctrines that include a bonus to surface detection
7. In La Résistance you can creat a spy network in that country, capture agents, crack cypher and use spy planes to gain naval intel.

• Sub visibility. Sub visibility is a value that represents a submarine's outline. This value is the "hide in shadows" score. The higher the value, the more visible a submarine becomes making it more likely to be spotted and attacked. The smaller the value, the less visible the submarine becomes making it harder to spot.
• Sub detection. Sub detection is a ship's ability to detect enemy submarines. A fleet can only engage submarines if it knows they're there. A submarine starts out hidden and has a chance to be spotted if it gets too close to an enemy ship (submarines may also be spotted by aircraft). Destroyers are best at hunting submarines followed by light cruisers due to their high sub detection ability and use of depth charges. Capital ships are poor at sub hunting due to their low sub detection and lack of depth charges. Sub detection may be increased by the following means:

1. Adding more ships, especially destroyers and light cruisers, to a fleet or sea region
2. Adding more planes to a sea region (gaining Air Superiority)
3. Increasing radar in a sea region
4. Having better decryption than an enemy vessel's encryption (+20% improved detection for every level that your decryption is better than the enemy's encryption, reference Defines NNavy DECRYPTION_SPOTTING_BONUS = 0.2)
5. Researching higher level destroyers and light cruisers
6. Creating destroyer and light cruiser variants incorporating higher sub detection
7. Hiring an escort fleet design company such as the United Kingdom's Yarrow Shipbuilders (+10% sub detection for screen ships)
8. Researching naval doctrines that include a bonus to sub detection
9. Adding an anti-submarine specialist (+10%), anti-submarine expert (+15%), or anti-submarine genius (+20%) to the military staff
10. In La Résistance you can create a spy network in that country, capture agents, crack cypher and use spy planes to gain naval intel.

Hulls

Hull type	Icon	Hull	Service Manpower	Surface detection	Sub detection	Surface visibility	Sub visibility	Depth charges	Max Speed (kn)	Max Range (km)	HP	Module Slots	Reliability % (Θ)	Fuel Usage	Production Cost	Resources
Destroyer		Early	250	20	1	10		1	25	1500	25	8	80 (64)		400	2
		1936	325	20	1	10		1	25	1800	40	8	85 (68)		500	2
		1940	400	20	1	10		1	25	2000	50	9	90 (72)		550	3
		1944	500	20	1	10		1	25	2500	60	10	92 (73)		600	4	1
Cruiser		Coastal Defense Ship	1800	20	1	20			15	1500	100	11	80 (64)	20	3500	3
		Panzerschiff	1800	20	1	22			20	7500	220	11	80 (64)	20	3500	3
		Torpedo	960	20	1	15			25	4000	140	12	90 (72)	20	1700	3
		Early	600	20	1	15			20	2500	100	10	80 (64)	20	1800	1
		1936	800	20	1	15			25	3000	110	11	85 (68)	20	1900	2
		1940	1200	20	1	15			27	4000	120	12	90 (72)	20	2000	2
		1944	1400	20	1	15			28	4500	130	12	95 (76)	20	2100	3
Battleship		Pre-Dreadnought	3200	20	1	20			13	2250	300	10	65 (52)	67	3000	1	1
		Super Heavy	9000	20	1	20			22	4500	700	14	80 (64)	75	5500	1	1
		Early	4000	20	1	20			20	3000	350	11	80 (64)	67	3300	1	1
		1936	5200	20	1	20			22	3500	370	11	85 (68)	67	3400	1	1
		1940	6000	20	1	20			24	4000	400	12	90 (72)	67	3500	1	1
		1944	6000	20	1	20			26	4500	450	12	95 (76)	67	3600	1	1
Carrier		Converted Cruiser	1000	26	5	30			20	4000	125	6	65 (52)	87	2700	3	1
		Converted Battleship	5000	26	5	30			23	4000	325	7	65 (52)	87	2700	4	1
		1936	4500	26	5	30			26	3000	250	7	70 (56)	87	2450	3	1
		1940	5000	26	5	30			26	4000	325	8	75 (60)	87	2600	4	1
		1944	5500	26	5	30			26	5000	350	9	80 (64)	87	3250	4	2
Submarine		Cruiser	200	20		1	20		11	5000	30	5	75 (60)	1	390	2
		Early	200	20		1	25		14	2500	10	3	60 (48)	1	220	1
		1936	200	20		1	20		14	4000	20	3	70 (56)	1	250	2
		1940	200	20		1	15		15	5000	30	5	75 (60)	1	320	2
		1944	200	20		1	12		16	6000	35	5	80 (64)	1	450	3	1

Θ Other than the Hull, only Engine and Fire Control modules affect Reliability. Since all Engine modules across all ship types provide the same flat 20% reduction, that is represented in the parenthesis above.

Modules

Module Type	Module	Service Manpower	Surface detection	Sub detection	Surface visibility	Sub visibility	Armor	Light Attack	Light Piercing	Heavy Attack	Heavy Piercing	Torpedo Attack	Depth charges	Anti-Air	Minelaying	Minesweeping	HP	Max Speed	Reliability (%)	Fuel Usage	Production Cost	Resources
Engine	Light Engine I																	5, 21%	-20%	7	90
	Light Engine II																	5, 32%	-20%	8	120
	Light Engine III																	5, 42%	-20%	10	150
	Light Engine IV																	5, 47%	-20%	10	170
	Cruiser Engine I																	5, 20%	-20%	12	400
	Cruiser Engine II																	6, 30%	-20%	16	480
	Cruiser Engine III																	7, 35%	-20%	20	550
	Cruiser Engine IV																	7, 40%	-20%	24	670
	Heavy Engine I																	7, 20%	-20%	20	1800
	Heavy Engine II																	10, 30%	-20%	25	2200
	Heavy Engine III																	11, 40%	-20%	30	2600
	Heavy Engine IV																	12, 45%	-20%	35	3000
	Carrier Engine I																	5, 20%	-20%	12	400
	Carrier Engine II																	5, 30%	-20%	16	480
	Carrier Engine III																	5, 40%	-20%	20	550
	Carrier Engine IV																	5, 45%	-20%	24	670
	Submarine Engine I																	5, 5%	-20%	7	90
	Submarine Engine II					-5%												5, 10%	-20%	8	120
	Submarine Engine III					-10%												5, 15%	-20%	10	150
	Submarine Engine IV					-15%												5, 20%	-20%	10	170
Battery	Light Battery I							1	1									-1%			90
	Light Battery II							1.5	2									-1%			120
	Light Battery III							2	2.5									-1%			150
	Light Battery IV							3	2.5									-2%			175	1
	Light Cruiser Battery I							4	5.5								20	-3%			225
	Light Cruiser Battery II							5	7								20	-4%			275
	Light Cruiser Battery III							6	8								20	-4%			300	1
	Light Cruiser Battery IV							7.5	9								20	-5%			350	1
	Heavy Cruiser Battery I				3.5					6.75	18						40%	-4%			750	1
	Heavy Cruiser Battery II				3.5					7.25	21						40%	-6%			800	1
	Heavy Cruiser Battery III				3.5					7.75	24						40%	-7%			825	2
	Heavy Cruiser Battery IV				3.5					9	27						40%	-8%			900	2
	Heavy Battery I									11	31							-5%			1275	1
	Heavy Battery II									12	36							-8%			1350	1
	Heavy Battery III									13	40							-9%			1450	1
	Heavy Battery IV									15	43							-10%			1650	1	1
	Super Heavy Battery									16	50							-10%			1800	1	1
	Dual-Purpose Main Battery							3	2					3				-2%			300	1
Secondary Battery	Secondary Battery I							3	5.5									-2%			180
	Secondary Battery II							4	7									-2%			240
	Dual-Purpose Secondary Battery							4.5	8					2.5				-3%			290
Anti-Air	Anti-Air I													1.5, 10%				-1%			90, 2.5%
	Anti-Air II													2, 10%				-1%			120, 2.5%
	Anti-Air III													3, 12.5%				-1%			150, 2.5%
	Anti-Air IV													4, 15%				-1%			190, 2.5%
Torpedo Launcher	Torpedo Launcher I											18						-1%			90
	Torpedo Launcher II											27						-1%			120
	Torpedo Launcher III											36						-1%			150
	Torpedo Launcher IV											45						-1%			180
Torpedo Tubes	Torpedo Tubes I											14									80
	Torpedo Tubes II											18									100
	Torpedo Tubes III											22									120
	Torpedo Tubes IV											28									140
Armor	Cruiser Armor I						6										0%	-5%			10%
	Cruiser Armor II						8										5%	-7.5%			15%	1
	Cruiser Armor III						10										10%	-10%			20%	1	1
	Cruiser Armor IV						12										15%	-12.5%			25%	2	1
	Battleship Armor I				10		26										5%	-20%			20%	1
	Battleship Armor II				10		31										10%	-20%			20%	1
	Battleship Armor III				10		40										15%	-20%			20%	2	1
	Battlecruiser Armor I				8		20										5%	-10%			7.5%
	Battlecruiser Armor II				8		25										10%	-10%			7.5%	1
	Battlecruiser Armor III				8		30										15%	-10%			7.5%	1	1
	Super-Heavy Armor				10		55										10%	-25%			25%	2	1
	Flight Deck Armor						5										25	-5%			10%	1
Fire Control Systems	Fire Control 0							5%		5%											60
	Fire Control I							10%		10%				10%					-5%		90
	Fire Control II							15%		15%				15%					-7.5%		120
	Fire Control III							20%		20%				20%					-10%		180
Sonar	Hydrophones			4																	40
	Active Sonar			7																	60
Radar	Radar I		5																		80
	Radar II		7	2																	110
	Radar III		12	6				5%		5%				5%							140
	Radar IV		18	14				10%		10%				10%							170
Anti Submarine Warfare	Depth Charge I												8					-2%			90
	Depth Charge II												12					-2%			120
	Depth Charge III												16					-2%			150
	Depth Charge IV												20					-2%			180
Mine Warfare	Minelaying Tubes														1						90
	Minelaying Rails														1			-2%			90
	Minesweeping Gear															1		-2%			30
Hanger Space	Hanger Space	500																-5%			2000	1
Aircraft Facilities	Floatplane Catapult		7	2.5														-1%			150
	Improved Floatplane Catapult		10	3.5														-1%			170
Snorkel	Basic Schnorkel					-10%															50
	Improved Schnorkel					-20%															70

Warfare

Mechanics

Events and Decisions

Events • Decisions