Submarine attacks in War on the Sea can be incredibly powerful, sinking huge amounts of tonnage while risking very little. However, the most effective way to use your submarines isn't always intuitive, nor is it necessarily obvious how you should go about hunting down your enemy's submarines. If you're unfamiliar with WWII era submarine and anti-submarine tactics I hope that this guide can help you get started.

I'll firstly be covering some basic concepts and historical context, so if you're already familiar with this information please feel free to scroll down to the actual gameplay tips located below.

WWII era submarines spent most of their time on the surface, using diesel engines to travel the long distances to their patrol areas and only submerging to attack or evade. While submerged, they used electric batteries for propulsion, and were much, much slower. On the surface, subs were faster than merchants but slower than other warships. Submerged, the subs were slower than everything else by a wide margin.

The main armament of all submarines was the torpedo, spreads of which could be launched while submerged at periscope depth to hopefully catch the enemy unaware. They were also typically armed with a light anti-aircraft gun and a deck gun, which could be used (very rarely) to attack surface targets and in some navies could also fire flak.

The US subs available in the game's Guadalcanal campaign consist of the Tambor and Gato classes. These were "fleet submarines," larger than the subs of other navies and designed to keep up with and scout for the surface fleet across the vast distances of the Pacific. The Tambor is distinct from the Gato in that it is very slightly slower, and cannot dive as deep. The succeeding Balao and Tench classes, which can dive even deeper, are modeled in game but are unavailable for the campaign.

In 1942 US subs are armed with the (historically very unreliable) Mark 14 torpedo, which in game will travel ~9000 yards at 30.5 kn. The subs have both passive and active sonar and, very usefully, surface and air radar. Many Japanese ships have excellent passive sonar, so you will want to avoid using the active sonar most of the time or you will give away your presence. By contrast, most Japanese ships have no radar to speak of, so you will be able to use your own with near impunity.

The Japanese subs available in game are the Type B1 and Type B1 Mod. 1, which for the purposes of the game are identical aside from a very small difference in mass. These were even larger than their American counterparts and even featured a catapult launched scout plane that was stored in a compartment on the deck, a feature fully modeled in game.

In 1942 Japanese subs were armed with the excellent Type 95 torpedo, a variant of the famous Type 93 "Long Lance" torpedo used by Japanese destroyers. In game it will travel ~8000 yards at a very fast 46 kn, which gives you somewhat more versatility regarding which targets you can attack and when. Historically, the Type 95 also had a larger warhead than the Mark 14, which I suspect may be modeled in game but don't know for sure. The Type B1 and B1 Mod. 1 subs have comparable active sonar and better passive sonar than American subs, but no air radar.

As mentioned previously, in 1942 the Mark 14 torpedo was notoriously unreliable: it would run too deep, detonate too early or not at all, and in some horrifying cases the gyro would fail and the torpedo would circle around towards the sub that fired it. This is modeled in game as a much higher rate of duds for the Mark 14: in the region of 33% duds vs. around 5% duds for the Type 95. If you're playing with duds enabled (which you should be, to experience that authentic submarine skipper pain) as the US this will need to be taken into account.

The main type of ship used for anti-submarine warfare in game is the destroyer. Destroyers are extremely fast, maneuverable, equipped with passive and active sonar, and capable of launching patterns of depth charges off their sterns to damage submerged subs. There are many different classes of destroyers in both the Japanese and US navies, but for the purpose of in game ASW all of the destroyers within a given navy are about as capable as the next. One thing to note is that Japanese ships have better passive sonar than US ships, so if you're playing as the US you will need to be more careful with your subs' noise levels.

There are a handful of exceptions worth mentioning:

On the US side, Atlanta class light cruisers are also equipped with sonar and depth charges, though their lower speed and larger size relative to destroyers makes them somewhat awkward in an ASW role.

On the Japanese side, The Momi class destroyers, among the oldest and smallest destroyers in the Japanese navy, have neither sonar nor depth charges. The Oyodo class light cruisers are equipped with passive and active sonar, but are only capable of dropping depth charges one at a time off the stern in a much less effective pattern. Amusingly, several classes of Japanese heavy cruiser are also equipped with passive sonar and depth charges, again dropped one at a time. Actually hitting anything with these huge ships and weak patterns is a tall order, but it can be pretty funny. Lastly, Japanese battleships and carriers are equipped with passive sonar, and while they have no depth charges, they will attempt to evade your subs if they detect you.

Detecting enemy submarines and avoiding detection for your own subs revolves entirely around sonar, and understanding it is vital to success and survival. There are two types of sonar: passive and active.

Passive sonar essentially just involves sticking microphones into the water and listening for the sounds made by enemy ships: the engines, the sound of turbulence around the hull, and any noise the crew might be making inside. This is limited by contact noise level, the distance from the contact, the local sea conditions, and any masking noise the listening ship may be making.

Active sonar involves making some kind of noise and listening for the echo bouncing off the hulls of enemy ships (this is the high pitched "ping" noise you hear on TV literally every time a submarine is on screen). Active sonar has the advantage of being able to detect contacts that are being perfectly silent, and it allows the listening ship to build a target solution very quickly. It has the disadvantage that it involves continuously making a lot of very loud noise, which will immediately alert any nearby vessels with passive sonar to your presence. What's worse, active sonar needs to travel all the way to the target and back in order to detect a contact, whereas it only needs to travel as far as the enemy ship in order to be heard via passive sonar. This means that enemy ships can hear your active sonar at a much longer range than you can use it to detect the enemy.

For surface ships this hardly matters: surface ships are so noisy and obvious than any nearby subs almost certainly already know they're there, and WWII era subs can't realistically do anything to harm a maneuvering destroyer anyway. There is no harm to turning on the active sonar on your destroyers when hunting for enemy subs. By contrast, a submarine's best defense is to remain hidden, and turning on the active sonar is a sure way to let everyone know you're there. This is not recommend unless dodging depth charges is your hobby. Active sonar is limited by distance to contact, the size of the contact (bigger ships reflect more sound), the facing of the contact (a side-on contact will reflect sound waves more strongly), local sea conditions, and again the amount of noise the listening ship is making. Having the seabed close behind a submarine will also make it harder to detect with active sonar, since it's harder to distinguish the return from the contact vs. the return from the sea floor.

Ships that are traveling faster will make more noise due to louder engines and greater turbulence around the ship's hull. This will make the ship easier to detect via both passive and active sonar (turbulence helps to reflect active sonar sound waves). Higher speeds will also make the ship's passive and active sonar less effective, as it will be harder to hear the noise of enemy contacts over the noise the listening ship is making. Both surface ships and submarines also have an area directly behind them called the "baffles," where they can't detect anything by either active or passive sonar.

All sonar is affected by the local sea state, which in game is indicated as 0 through 8, with 0 being the calmest seas and 8 being the roughest seas. Rough seas create a lot of ambient noise, which makes listening for enemy contacts much harder. In sea states 0 through 3, submarines can usually be located with relative ease. In sea states 4 and 5 surface ships will need to be going slow and close to pick up a contact. At sea states 6 and above ships will have to be perfectly stationary and directly above an enemy sub in order to hear it, if it's even possible at all.

(Edit: after having had more opportunity to use the IJN destroyers, I've realized their incredibly sensitive passive sonar can regularly find US subs even in sea state 6. There isn't ever really any reason to turn on your active sonar while playing as Japan. It's honestly kind of overpowered, and will probably continue to be so long as the game instantly tells you the precise location and depth of a contact immediately when you pick it up on passive sonar).

If the seas are relatively calm there may also be a thermal layer, which is a depth at which the temperature of the ocean drops sharply. Thermal layers tend to reflect sound waves away from the layer, which makes it harder for ships on opposite sides of the layer to hear each other. Sound waves created above the layer will also tend to bounce between the surface and the layer, which creates a "duct" in which sound waves will travel much farther than they would otherwise. The layer depth, strength, and strength of the duct are available in the menu. A strong layer can help your submarines avoid detection and make getaways in quiet seas where escape would otherwise be impossible.

I also suspect that cavitation may play a roll in sub detection, depending on the fidelity of the WotS sonar model. This is pure conjecture on my part, since it's not mentioned anywhere in the manual, but cavitation itself seems to be modeled in the game so it seems worth mentioning. Cavitation is when the propeller of the ship is spinning hard enough to turn some of the water around it to gas, and it is extremely loud. You can tell whether or not your subs are cavitating by the presence or absence of bubbles around the propeller. The deeper your sub is, the faster it can go without cavitating. Again, no idea whether noise from cavitation is actually used for passive sonar detection in game, but it can't hurt to avoid it when possible.

in the campaign, your subs are best used as scouts, convoy raiders, and to pick off any large warships that happen to wander past. Subs cost very few command points and can be deployed in large numbers, so you'll want to deploy a number of them between the enemy home port and any important objectives in order to intercept convoys. It's also useful to have a bunch of them positioned around your important fleets, especially your carriers, to detect and harass any enemy surface groups that might otherwise catch you by surprise.

When attacking an enemy surface group, you'll need to prioritize your targets carefully. You are realistically only going to get one spread of torpedoes away before you have to disengage. This is for two reasons: firstly, as soon as your torpedoes hit anything, the other ships will begin evading, making it very difficult to hit them with any follow up attacks. Secondly, on torpedo impact any escorts will immediately begin making a beeline for the location where you launched the torpedoes from, and it is very much in your best interest not to be there when they arrive.

Targeting destroyers and light cruisers is generally not advisable, given that they are difficult to hit and not worth many command points. If there is only one destroyer guarding a convoy, however, it might be worth trying to knock it out first so that you can reengage the convoy later and attack with no risk of reprisal. If you do manage to successfully get a spread off on a destroyer or light cruiser, it will only take one or two hits to sink it.

(Edit: USN light cruisers are much larger than their IJN counterparts and are very durable.
Something like a Cleveland class cruiser is a worthy target and you should expect around three good hits a the very least to sink one)

Heavy cruisers, battleships, or (the Holy Grail) carriers are much better targets. They're larger, slower, worth a bunch of command points, and even if you don't sink them that's still a lot of firepower out of the fight for the near future. It's worth giving these a full spread of torpedoes, since depending on the difficulty you're playing at the largest ships can sometimes eat even a full spread and still stay afloat, especially if you're using Mark 14's.

When attacking convoys, it's best to go for oilers first. Oilers are larger, worth more command points, and no matter how much engineering equipment and supplies the enemy has they won't be able to upgrade their ports and airfields without any oil. A full oiler is also extremely flammable, understandably, so if you manage to start any kind of fire at all it's likely to grow into a raging inferno that will take the whole thing down.

I have experimented somewhat with using groups of subs in "wolf pack" attacks. It allows you to really ruin the day of any one particular surface group at the expense of having much less coverage over the wider area. It also requires very careful coordination of your torpedo attacks: if one torpedo spread arrives much earlier than the others, then your other targets will begin maneuvering and those other spreads will likely miss. Personally I prefer the enhanced scouting and reduced micromanagement of using lone subs, but your preferences may vary.

When you first begin an encounter with an enemy surface group, your sub(s) will spawn submerged and likely ahead of the enemy group, in a good position to make a torpedo attack. The very first thing you need to decide is whether you're going to make an attack at all. Your biggest two concerns are the composition of the surface group and the local sonar conditions. If the surface group is just a few destroyers, it's probably worth saving your torpedoes for a convoy or large warship.

The best sonar conditions in which to make an attack are during high seas or in the presence of a strong thermal layer, which will make it much easier to make your escape after your attack. Attacking during quiet seas with no thermal layer will nearly guarantee that the enemy escorts will be able to find you, which tends to have a strongly negative effect on your submariners' life expectancy. Also, if the enemy escorts are going to be within about 2000 or 3000 yards of your sub when you make your attack, it will make it much more difficult to get away. Finally, you should bear in mind that you can only reasonably attack a ship with a constant heading and speed. If your target is maneuvering or changing speed, it's not worth wasting your torpedoes. If you decide it's not worth attacking, just set your speed to 0, go to ultra quiet, and start the retreat timer.

Once you've decided to make your attack and chosen a target, you need to maneuver into position. Torpedo attacks are most accurate when the torpedoes impact the target side-on with a low gyro angle. This means that you want your sub's heading to be off by 90 degrees relative to the heading of your target. You also want the torpedoes to run as straight as possible without having to turn very much once they've armed. US subs have rear torpedo tubes and can attack while facing away, which makes it easier to begin your escape at the cost of only being able to fire a spread of 4 torpedoes instead of 6. Japanese subs only have forward torpedo tubes and need to be facing their target.

Once you're in position, kill your speed and wait for your target solution to build up. Your target solution will increase by correctly identifying your target and observing it using your scope, passive sonar, and radar (only if playing as the US: using your radar as the Japanese is not advisable as all US warships will be able to pick up your signal). Active sonar can also help, but you should only turn it on if there are no ships with any passive sonar in the entire surface group, which is very rare. Also, a few Japanese warships do in fact have radar, and you will want to make sure you're not facing one of them before turning on your radar or your radar signal will give you away.

While waiting for your target solution to build, select how many torpedoes to fire with what spread angle. When playing as the US, the Mark 14 is so unreliable that you're probably just going to want to go ahead and fire a full spread of six. You'll thank me when 5 out of those 6 turn out to be duds (yes, this has happened to me. No, I'm still not over it). With Japanese subs you can afford to be more frugal, and throw on maybe one more torpedo than you think you need on the off chance you get a dud.

If you want all your torpedoes to hit the same ship, an angle of 1 degree is best. If you just want to cause as much havoc as possible in a large, crowded convoy, you can crank it all the way up to 10 degrees. If your max firing solution is lower than 99%, usually due to low visibility, you'll want to increase your angle and add more torpedoes to taste.

Once your solution is as good as it's going to get, fire your torpedoes once the gyro angle is close to zero (you can see the gyro angle of the current solution by mousing over the torpedo room). Immediately set your depth the the lowest you can go (you can get away with going a bit lower than your test depth) and set a course away from the enemy escorts as fast as you can go. If you're in a strong duct, you may want to hold off increasing your speed until you're below the layer to avoid alerting the enemy prematurely. All going to plan, your enemy should be unaware right up until the torpedoes hit them, and you should be long gone by the time the escorts reach your firing position.

The steps to a successful getaway:

1. Get as far away as possible as fast as possible.
2. Get as deep as possible.
3. Face directly away from searching escorts, to minimize active sonar return.
4. Hug the seabed if possible, again to avoid active sonar.
5. Rig for ultra quiet to stop reloading noise.
6. If escorts are nearing your sub despite your efforts, slow to 1 or 2 kn to hopefully avoid passive detection.
7. (?) Avoid letting your sub cavitate (again, not sure if this is modeled)

Keep a close eye on the enemy escorts. If they're still heading towards where you were, you're still in the clear. If they start heading towards where you are, you have a problem.

If the enemy escorts pick you up on their sonar, you're in serious trouble. Dodging depth charges launched by a ship going 35 kn in a ship going 8-9 kn is a tall order. You want to be as deep as your sub can go, which will give you more time to dodge while the depth charges fall from the surface. Not getting blown out of the water will require a bit of luck, but here's a method I've found that seems to work.

1. Go to max speed and line up your heading with the heading of the incoming escort.
2. As soon as the depth charges start dropping, turn the rudder fully to port or starboard.
3. Pray.

If you survive that pattern of depth charges, the good news is that you're now in the escort's baffles, which means they've lost contact with you. Reduce your speed to 1-2 kn, turn away from the escort, and if the seas are noisy or there's a strong layer you might be able to slink away without being reacquired. More likely, the escort will turn around, find you again, and come in for another run, and you'll need keep dodging depth charges until your pursuers run out.

Japanese destroyers and the Oyodo class normally have 36 depth charges (though some of the early destroyer classes have more or less), enough for two patterns of 15 and one itty bitty pattern of 6. The Japanese heavy cruisers usually have 12 charges, and can only drop 5 at a time, but for some bizarre reason the Takao class has a whopping 60. Dodging twelve runs of 5 charges is easy, but tedious. US destroyers and the Atlanta class, meanwhile, all have 60 depth charges each, enough for four big runs, so buckle up.

Once the escorts run out of depth charges, they'll keep doing dry runs on your sub. I suppose technically the escorts could just keep following you until either you run out of battery/oxygen and need to surface or sonar conditions change and you can get away, but that would take hours and isn't modeled in game, so just start the retreat timer.

If you do take any damage from the depth charges, you're likely screwed. Your repair crew might be able to contain the flooding and let you keep going, but more likely those sections are destroyed and you're now sinking towards your crush depth. If the seabed is above your crush depth you can try to rest silently on the sea floor, which might give you just that little bit of an edge to confound enemy active sonar. If you should be so lucky, the enemy escorts will just keep circling your last known position ad infinitum, so go ahead and start the retreat timer.

If you're in deep waters, however, your last desperate measure is to do an emergency blow ballast and surface the ship. At this point you're essentially as good as sunk. Compared to the hulls of surface ships the pressure hull of a submarine might as well be made out of paper, and even an armed merchant will make short work of you if it catches you on the surface. The best you can hope for is to take a couple of spiteful shots with your deck gun and maybe knock out a turret or two before you go down fighting.

While I scarcely dare mention it, it is possible to exploit your way out of these chases by manipulating the very generous retreat timer system, but where's the fun in that? Submarine and escort chases are tense and exciting, and you'd essentially be opting out of playing the game you paid for. If you choose to sully your honor in this manner, I'll let you figure out how to do it on your own. Hopefully Killerfish will revamp the retreat timer system in the future to appease masochists like me.

In all this talk of sonar and escorts, I've neglected to mention probably the biggest threat to submarines: aircraft. WWII era subs spend most of their time on the surface, and it takes a minute or so for them to be able to start diving. This gives aircraft, if not spotted in time, the opportunity to drop bombs on the exposed subs. As such, when you start an encounter between your aircraft and an enemy sub the sub will start on the surface. A direct hit from pretty much any kind of air dropped explosive will blow a submarine's pressure hull wide open, either sinking the sub outright or forcing it to quickly resurface where it can be strafed to death.

Any time your recon planes spot an enemy sub on the campaign map, you should send a flight or two of bombers after it. Wait until you're nearly over the top of the sub before starting the encounter, and you're likely to be able to get your bombs off before it can dive. If you score a hit and don't get the notification that the sub is sinking, then start circling the area and wait. More likely than not, the sub will eventually be forced to blow ballast and resurface, at which point a few strafing runs will send it back beneath the waves for good. This may take a while, so turn on time compression and be patient.

Any kind of high explosive loadout will work wonders against the unarmored hull of a submarine, provided you land a direct hit. Avengers, however, are especially excellent sub hunters because they have access to rockets and air dropped depth charges. A volley of rockets from a flight of Avengers will turn any surfaced submarine into Swiss cheese, and depth charges will ensure that even a sub that's able to begin it's dive won't escape.

(Edit 6/15/2021 It seems that the visibility of enemy subs to aircraft on the campaign map has been drastically reduced. I haven't been able to find a single one with air patrols in my recent US campaign, despite the fact that they've been all over my surface groups. In light of this, surface ASW patrols should be considered that much more important.

I haven't tested this thoroughly, so take it with a grain of salt, but I suspect that the behavior of enemy subs spawning on the surface when only aircraft are in the tactical map is still in place. If you happen to know than an enemy sub is in a particular region, you may still be able to engage subs with aircraft by going to the tactical map manually.)

As for escorts, each of your surface groups should have at least two destroyers in its formation to hunt down any attacking enemy subs.

It's also very useful to establish dedicated ASW patrols, which should consist of two or three destroyers. Your navy's cheap, outdated destroyers make excellent candidates for these. You should primarily patrol the areas ahead of your important fleets and around where your convoys will be transiting.

When any of your surface groups (hopefully one of your ASW patrols) begins an encounter with an enemy sub, that sub will start at periscope depth having already launched a spread of torpedoes at your ships. This happens Every. Single. Time. Even if you began the encounter using aircraft, if any of your ships are in the combat area the enemy sub will magically teleport in front of your ships and launch a spread of torpedoes at them. Bear this in mind.

The very first thing you want to do is run the simulation for a few seconds, pause, and then look for the trail of the incoming torpedoes. When you find it, note where the trail is coming from, because that's where the enemy sub is. Maneuver any of your ships that are being targeted out of the path of the incoming torpedoes, turn on all your active sonar, and send your destroyers that aren't in danger towards the source of the torpedoes (this is why you always make sure to bring at least two destroyers).

Whether or not you'll be able to make sonar contact with the enemy sub is largely dependent on the local sonar conditions. In sea states 0-3, you could hear a pin drop inside that sub and it essentially just signed its death warrant by attacking you, in sea states 4-5 you're going to have your work cut out for you, and in sea state 6 you'll need to get very lucky and be almost directly over the sub in order to find it (Edit: unless playing as the IJN, see edit in "sonar" above). Don't even bother in states 7 or 8.

Remember: the faster your destroyers are moving, the less effective their sonar will be. You want to rush your destroyers over to where you think the sub is, kill off all your speed, and listen for a few seconds. Experience has caused me to believe that currently having your active sonar on interferes with your passive sonar (though I don't know why this would be) so while you're listening turn off your active for a few seconds, especially if you're using Japanese destroyers with their superb passive sonar. If you don't make contact with the enemy sub, fire your engine back up, move maybe 500 yards or so in a direction you think the sub might have gone, and stop again to listen. Bring your other destroyers into the area and continue this start/stop search pattern until you either find the sub or decide to give up. You need to strike a fine balance here: too slow and the sub will slip away, too fast and you'll cruise right over the sub without hearing it.

With a little luck, you'll pick up the contact, and at this point you've very nearly got her dead to rights. The AI is not nearly as good at dodging depth charges as you are. Begin lining your destroyers up for depth charge runs. In poor sonar conditions I find that it's sometimes a good idea to keep one destroyer as a "spotter," slowly shadowing the submarine so you don't lose contact while your other destroyers perform depth charge runs. Once you've got a destroyer pointed towards the sub and within about 500 yards, use the attack command to start a depth charge run. You could perform the run manually, but honestly it's kind of a pain and I find the auto attack gets the job done just as well.

Once you've managed to damage the enemy sub with your depth charges, it's all over but the crying. If it doesn't sink outright, it will be forced to blow ballast and resurface, at which point your destroyers' guns can rip it to shreds. Do note that the sub is liable to get off a few rounds with it's deck gun before it sinks, which might knock out something important on your destroyer with a lucky hit, so try to make sure the sub sinks as quickly as possible.