Anti-Submarine Warfare

Submarines (SS, also including "Aircraft Carrying Submarines" SSV) are characterized by relatively low armor and HP. By contrast, they are difficult to handle using "normal setups", requiring instead specific Anti-Submarine Warfare (ASW) equipment and setups in order to be sunk.

During sorties, submarines are typically found at pre-boss nodes, but some can be boss themselves, see here.

Attack Behavior

Unlike regular surface ships, submarines:

• Cannot be targeted by normal shelling attacks,
• Are immune to air and torpedo attacks,
• Cannot take more than scratch damage during night battle,
  • Therefore they cannot be sunk at night,
  • The exception to this rule is when a battle starts at night, or when attacking with a Combined Fleet.

ASW Shelling Conditions

Only certain ships meeting certain conditions can attack SS(V).

• Most often, if a ship can attack a submarine, focusing it will take over any other target.

Here, refers to any /.

Ship	Conditions		Day Battle	Night Battle
	Stats	Equipment
Taiyou-class Kai Ni Kaga Kai Ni Go	Not more than moderately damaged (中破)	with 1+	Prioritize SS	Night Air Attack will prioritize surface target Night Shelling prioritizes SS
Gambier Bay Mk.II				Cannot attack SS unless if: setuped for a Night Air Attack, then prioritize SS with a night shelling attack
All other CVL				Do not attack SS
Mogami-class Kou Kai Ni			Prioritize surface target
BBV, CAV, AV, LHA	None	Equipped with Bomber, , , , or with 1+	Prioritize SS
Fusou-class Kai Ni No.101 Transport Ship		Equipped with	Prioritize SS
Any CV, CVL, BBV, CAV, AV, LHA		Not equipped with the above-mentioned equipment	Do not attack SS
Hayasui Kai Yamashio Maru Kai		Equipped with	Prioritize SS	Do not attack SS
		Not equipped with	Prioritize SS
All other ships	At least 1 base ASW	None
	No base ASW		Do not attack SS

Notes

• As Abyssals also follow those conditions, SS/V can be used as "Submarine Tanks" (Sub-tanking) on some maps to deviate attacks from the fleet to the submarine.

Damage Calculation

The stats used to calculate damage against submarines is the ASW.

• When contributing to ASW power, Base ASW is square rooted, while equipment ASW is multiplied by 1.5.
  • Anti-submarine weaponry is therefore the primary source of ASW damage, with the base ship ASW playing a very minor role damage-wise.
  • However, base ship ASW is the primary determinant of whether a ship can reach 100 total ASW to perform "Opening ASW" (OASW) attacks.
• Unlike shelling, ASW damage is capped at 170.

ASW attacks have different modifiers gained from Formations,

• Line Abreast is the main ASW formation, with a 1.3x damage modifier,
• Cruising Formation 1 is the main ASW formation for Combined Fleets, with a 1.3x damage modifier.

Anti-Submarine Formula
[math]\displaystyle{ \text{Atk}_\text{base ASW} = \left( 2\sqrt{\text{ASW}_\text{ship} } + 1.5 \times \bigg[ \sum_\text{All Equipment} (\text{ASW}_\text{equip} + \uparrow \text{ASW}_\text{fit bonus} ) \bigg] + \bigstar + \text{Type}_\text{ship} \right) \times \text{Mod}_\text{synergy} }[/math] With [math]\displaystyle{ \text{ASW}_\text{equip} }[/math] is the stat of anti-submarine equipment and attack planes. This means that the stat is not included in the calculation for the following equipment types: Recon Seaplane Recons Seaplane Fighters Fighters Large Flying Boats Radars Main Guns [math]\displaystyle{ \uparrow \text{ASW}_\text{fit bonus} }[/math] unlike [math]\displaystyle{ \text{ASW}_\text{equip} }[/math] this is the from Fit Bonuses of all equipment. [math]\displaystyle{ \text{Type}_\text{ship} }[/math] a constant depending on the type of the ship performing the attack. See below for details. Ship Type Constant Ship Types [math]\displaystyle{ \text{Type}_\text{ship} }[/math] Coastal Defense Ships (DE) Destroyers (DD) Light Cruisers (CL/CT) Oilers (AO) (without carrier bomber) 13 Aviation Cruisers (CAV) Aviation Battleships (BBV) Seaplane Tenders (AV) Light Carriers (CVL) Landing Ships (LHA) Oilers (AO) (with carrier bomber) 8 [math]\displaystyle{ \text{Mod}_\text{synergy} }[/math] the synergy multiplier bonus from using certain combinations of ASW equips (see below).
Notes The bonuses do not stack, meaning only the highest possible bonus applies. The exception is the depth charge penetration detailed above. Multiple equipments of the same type still only apply the bonus once. There is an accuracy bonus as well but it is small. Stacking sonars will give a bigger accuracy bonus.

ASW Damage Synergy
Small Small Sonars	Type 93 Passive Sonar Type 4 Passive Sonar Type 3 Active Sonar Type 3 Active Sonar Kai Type124 ASDIC Type144/147 ASDIC HF/DF + Type144/147 ASDIC
Large Large Sonars	Type 0 Passive Sonar
DCP Depth Charge Projectors (DCP)	Type 94 Depth Charge Projector Type 3 Depth Charge Projector Type 3 Depth Charge Projector (Concentrated Deployment) Prototype 15cm 9-tube ASW Rocket Launcher RUR-4A Weapon Alpha Kai AP Mk.32 ASW Torpedo (Mk.2 Thrower) AP
DCR Depth Charge (Racks) (DCR)	Type 95 Depth Charge AP Type 2 Depth Charge AP Lightweight ASW Torpedo (Initial Test Model) AP Hedgehog (Initial Model) AP Type 2 Depth Charge Kai Ni AP
Other ASW Mortars	Type 2 12cm Mortar Kai Type 2 12cm Mortar Kai (Concentrated Deployment)
ASW Damage Modifiers: [math]\displaystyle{ \text{Mod}_\text{synergy} = {Mod}_\text{1} \times {Mod}_\text{2} }[/math]
[math]\displaystyle{ {Mod}_\text{1} }[/math]	+ (Any Sonar + Any Depth Charge)	1.15
[math]\displaystyle{ {Mod}_\text{2} }[/math]	DCP + DCR and NO Small	1.1
	Small + DCP + DCR	1.25
Examples
[math]\displaystyle{ \text{Mod}_\text{synergy} }[/math]	Small + DCP + DCR	1.4375[math]\displaystyle{ 1.15 \times 1.25 }[/math]
	Large + DCP + DCR	1.265[math]\displaystyle{ 1.15 \times 1.1 }[/math]
Armor Penetration
Indepentant of synergies, some equipment provides additional armor penetration to ASW attacks. The affected equipment are: DCR: Type 95 DC, Type 2 DC, Lightweight ASW Torpedo, Hedgehog, Type 2 DC K2 DCP: RUR-4A Weapon Alpha Kai, Mk.32 ASW Torpedo (Mk.2 Thrower). The flat armor penetration value is calculated as follows: [math]\displaystyle{ \text{Pen} = \sum\limits_{\text{Equipment}} \Big( \sqrt{\text{ASW}_\text{Equipment} - 2} + \text{Mod}_\text{ship} \Big) }[/math] With [math]\displaystyle{ \text{ASW}_\text{Equipment} }[/math] the base ASW stat of the applicable equipment, Visible Bonuses and Improvements are not counted here. [math]\displaystyle{ \text{Mod}_\text{ship} }[/math] being 1 for DE, 0 otherwise, Note Armor penetration from equipment stacks, The final armor of the targetted submarine cannot go below 1.

Evasion

Submarine Equipment provide an evasion bonus to submarines against ASW attacks (around 1.2).

• See Evasion for more details.

Opening ASW Shelling (OASW)

Commonly referred to as OASW (opening ASW). All eligible ships will perform a regular ASW Shelling attack, following range order in the same fashion as the First Shelling Phase. As these opening attacks happen before the Opening Torpedo Salvo, they may disable or even sink enemy submarines before they have a chance to attack.

OASW has the following trigger conditions:

• Only ships listed below can trigger an OASW,
  • The ship is not required to be able to perform any ASW Shelling.
• They must meet their specific ASW stat threshold and requirements, listed below,

OASW Ship	ASW Stat Required	Equipment Required
Any DD, CL, CLT, CT, AO	100+ ASW	1 Sonar Equipped
Kai Ni Juu		+ Bomber / / / Sonar + Any Seaplane Bomber, or Rotorcraft, or Liaison Aircraft, or Dive Bomber, with 1+ ASW
		+ Bomber / / Sonar + Seaplane Bomber, or Rotorcraft, or Depth Charge
Any CVL		+ / / / Sonar + Any with 1+ ASW
	50+ ASW	+ / / Sonar + Any with 7+ ASW
	65+ ASW	/ / Any with 7+ ASW
Any DE	60+ ASW	1 Sonar Equipped
	75+ ASW	Total of 4+ ASW from equipment
Kai Ni D Fletcher-class John C. Butler-class Kai/Mk.II J-class Kai	Can OASW innately
Kai Ni Go	N/A	/ / / Any with 1+ ASW
	N/A	2 Autogyros -or- 1 Helicopter

See the list of Anti-submarine Weaponry and ASW Aircraft to better see what can help achieve OASW on a given ship.

Abyssals

Abyssal ships do not follow these rules. The following may perform OASW unconditionally:

• Destroyer Ha-Class Late Model Elite
• Destroyer Ni-Class Late Model Elite
• Light Cruiser Tsu-Class Flagship
• Light Carrier Nu-Class (Elite III, Elite IV, all Kai Elite, all Kai Flagship)
• Ancient Destroyer Princess II
• Seaplane Tender Water Princess (all variants)
• Abyssal Kuriles Princess (all variants)
• Destroyer Forest Princess (Damaged variants unconfirmed)
• American Destroyer Princess (most variants)

Other abyssals cannot perform OASW.

LBAS

See the Land-Based Air Squadron page

• Only ASW Planes (7+ ASW) can attack submarine during this phase.
  • If submarines are present, those planes will prioritize attacking submarines, while other attackers will only be able to attack surface targets.

ASW Aircraft
Rotorcraft	Autogyros	Ka Type Observation Autogyro O Type Observation Autogyro Kai O Type Observation Autogyro Kai Ni
	Helicopters	S-51J S-51J Kai
Liaison Aircraft		Type 3 Command Liaison Aircraft (ASW) Type 3 Command Liaison Aircraft Kai Type 1 Fighter Hayabusa Model II Kai (20th Squadron) Type 1 Fighter Hayabusa Model III Kai (Skilled/20th Squadron) Type 3 Command Liaison Aircraft Kai 2
Land-based Patrol Aircraft		Prototype Toukai Toukai (901 Air Group)
+7 ASW Torpedo Bombers		Type 97 Torpedo Bomber (931 Air Group) Type 97 Torpedo Bomber (931 Air Group/Skilled) Tenzan (931 Air Group) Prototype Type 97 Torpedo Bomber Kai (Skilled) No. 3 Model E (w/ Type 6 Airborne Radar Kai) Tenzan Model 12A Kai (Skilled w/ Type 6 Airborne Radar Kai) Ryuusei Kai (CarDiv 1/Skilled) Swordfish Mk.III (Skilled) Barracuda Mk.III TBM-3D TBM-3W+3S Tenzan Model 12A Kai 2 (Murata Squadron w/ Radar)
+7 ASW Dive Bombers		Ju 87C Kai Ni (w/ KMX) Ju 87C Kai Ni (w/ KMX/Skilled) Type 0 Fighter Model 64 (Two-seat w/ KMX)
+7 ASW Seaplanes	Recons	Type 0 Reconnaissance Seaplane Model 11B Type 0 Reconnaissance Seaplane Model 11B (Skilled)
	Bombers	Swordfish Mk.III Kai (Seaplane Model) Swordfish Mk.III Kai (Seaplane Model/Skilled) Zuiun Kai Ni (634 Air Group/Skilled)

ASW Support Expedition

See ASW Support Expedition

• If a CVL is present, aircraft with ASW will attack submarines regardless of the ship on which it's equipped.

See Also

• Anti-Submarine Setup
• ASW Equipment
• ASW Modernization
• Partials/Opening ASW