The unreasonable effectiveness of submarines

[Akela]

Thanks, unfortunately the values mean nothing to me (1.25% per convoy vessels or per convoy?, 1.25 units? Etc etc) so i can only guess at the mechanics. So below is complete guesswork:
this assumes that every one convoy vessel sunk is a 1.25% loss in efficency.

I don't think that it's a fixed quantity per convoy - it looks like a multiplier on the percentage of the total convoys needed for the route.

    CONVOY_EFFICIENCY_LOSS_MODIFIER = 1.25,                            -- How much efficiency drops when losing convoys. If modifier is 0.5, then losing 100% of convoys in short period, the efficiency will drop by 50%.
    CONVOY_EFFICIENCY_REGAIN_AFTER_DAYS = 7,                        -- Convoy starts regaining it's efficiency after X days without any convoys being sink.
    CONVOY_EFFICIENCY_REGAIN_BASE_SPEED = 0.04,                        -- How much efficiency regains every day.
    CONVOY_EFFICIENCY_MIN_VALUE = 0.05,                                -- To avoid complete 0% efficiency, set the lower limit.

If I'm reading those right, you need to sink 1/1.25 = 80% of the convoys to drop efficiency to zero (theoretically - those defines also list a 5% floor on efficiency, so you'll never actually hit zero). If this is a 5-convoy route carrying resources, you can wipe it out by sinking four subs - if it's a 100-convoy route supplying an entire army, you'll need to catch 80 to have the same effect.

again, too many variables, however you can take an educated guess and assume that the larger sub fleet will be less effective then the smaller sub fleet, as the smaller fleets will be less likely to be completely intercepted by asw vessels.

It's not quite that simple. If the enemy has <100% escort coverage, the large fleet may actually be better at beating the ASW squadrons due to alpha-striking.

If you're below 100% coverage, your escorts don't arrive on battle start, they reinforce slightly later on. Against a small sub fleet, this isn't too important - the subs get a free shot or two, but you should arrive in time to save most of the convoys since they just don't have enough damage to kill everything before you get there. Put all the subs together into one fleet, though, and they can just wipe half the convoys with the first volley, and the escorts only arrive in time to watch the wrecks sink while the subs just sail away to do the same thing again somewhere else.

 

[KubiG37]

What a battle. A black day for Royal Navy.

And UK AI is actually pretty much the only AI that upgrades its ships in the slightest (especially the ASW, thanks to AI scripts), every other AI just either doesn't upgrade their designs for whatever reason even when they have the XP, or outright not even bother researching the naval techs.

Quite sad after so many patches.
MTG is a game system that clearly never had an AI in mind, they only teached it how to not make it crash the game basically.

 

[HugsAndSnuggles]

It's not quite that simple.

It's not all about coverage, either: task force can only participate in a single battle at a time, so if you have 10 wolfpacks active in the area, while enemy simply doomstacked their ASW, 9 out of 10 wolfpacks will hunt unmolested >.>

 

[GSP Jr]

The fact that this is all after MtG is really pretty sad.

 

[MinhowMinhow]

What are you guys doing? Every time I use subs they always get sunk, even in low aggressive convoy raiding when a few DDs show up. Even my lvl.3 subs gt sunk by AI lvl.1 DDs. I use them more as a minelayer and use airpower to sink ships.
What are the designs? Doctrines? Composition? Missions? Are they good as a strike force?

 

[Reman]

What are you guys doing? Every time I use subs they always get sunk, even in low aggressive convoy raiding when a few DDs show up. Even my lvl.3 subs gt sunk by AI lvl.1 DDs. I use them more as a minelayer and use airpower to sink ships.
What are the designs? Doctrines? Composition? Missions? Are they good as a strike force?

Subs aren't very good in straight battles, as even crappy 1918 DDs are good enough at evasion-tanking torps long enough for subs to be revealed. Lopsided kill ratios like the one the OP posted are typically due to either the enemy running out of fuel, fighting in mined waters, the naval results window glitching and not showing thousands of friendly NAVs, or some combination of the 3.

 

[DGuller]

Subs aren't very good in straight battles, as even crappy 1918 DDs are good enough at evasion-tanking torps long enough for subs to be revealed. Lopsided kill ratios like the one the OP posted are typically due to either the enemy running out of fuel, fighting in mined waters, the naval results window glitching and not showing thousands of friendly NAVs, or some combination of the 3.

You're mistaken. I pretty much always use all-sub navies in my games, regardless of countries, and they always get the job done destroying the enemy fleets. This one battle was a more dramatic example, but it still happens regularly. I just chose to take the screenshot this time, partly because there are no compounding factors. My subs didn't have air cover, I wasn't mining the water, and I only had 12 subs to start from.

The way to get these results reliably is to do everything to reduce your sub visibility and your torpedo reveal chances. For this particular game, I gave Donitz "Silent Hunter" and then the next two sub promotions, I maxed out the right branch of the trade interdiction, I used the sub naval design company, I researched electric torpedoes, and obviously I used 1940 subs with snorkels. Just stack all the torpedo reveal modifiers, visibility modifiers, and then attack modifiers (the more attack you have, the quicker you dispose of fleets to move on to the next one, as sometimes you can get stuck in a bottle for a couple of months).

I don't even bother with earlier subs in battles. Maybe I use them as mine-layers, but honestly I don't bother anymore, I can dispose of fleets just fine without mines. I use them for training but then delete them once I'm up and running with 1940 subs.

 

[DGuller]

I just remembered that I took a screenshot earlier in the battle, so here it is. Maybe you'll see something and point it out, but even if something exceptional did happen, it must happen often enough, because I always manage to delete enemy fleets in all my games with subs.

Just to reiterate, this was off the coast of Portugal, so I had no way of putting any planes in the air as Germany there, I didn't mine anything, and at least GB was definitely not out of fuel (I know because my goal was to run them out of fuel, so I was checking intel regularly, and they never did run out of fuel before I landed on their shores).

 

[DicRoNero]

because I always manage to delete enemy fleets in all my games with subs.

Hopefully more people will play this way so that there won't be any illusions left regarding the present quality of the naval game.

Meanwhile, I for one will keep re-rolling my admirals to always get that politally connected one - because we all know that promoting admirals [above their starting rank] is both costly and very important.

 

[STABBY5]

the ability of subs to fire while attempting to disengage

This is a symptom of a larger problem. If you set subs to always engage or engage at high risk their performance becomes insane, sinking entire fleets. The torpedo attack is way too high and the submarine traits are way too powerful. Especially the one that reduces torpedo cooldown.

The game doesn't really model ambush combat of submarines. Their normal attacks have to be very good to sink convoys which means if you use them in battle they are far better than they should be. The fact that every ship is always in range of them is a problem with torpedoes and less so guns. And armor doesn't do anything to stop them which is nonsense. Larger ships especially had dedicated torpedo protection.

 

[Reman]

You're mistaken. I pretty much always use all-sub navies in my games, regardless of countries, and they always get the job done destroying the enemy fleets. This one battle was a more dramatic example, but it still happens regularly. I just chose to take the screenshot this time, partly because there are no compounding factors. My subs didn't have air cover, I wasn't mining the water, and I only had 12 subs to start from.

The way to get these results reliably is to do everything to reduce your sub visibility and your torpedo reveal chances. For this particular game, I gave Donitz "Silent Hunter" and then the next two sub promotions, I maxed out the right branch of the trade interdiction, I used the sub naval design company, I researched electric torpedoes, and obviously I used 1940 subs with snorkels. Just stack all the torpedo reveal modifiers, visibility modifiers, and then attack modifiers (the more attack you have, the quicker you dispose of fleets to move on to the next one, as sometimes you can get stuck in a bottle for a couple of months).

I don't even bother with earlier subs in battles. Maybe I use them as mine-layers, but honestly I don't bother anymore, I can dispose of fleets just fine without mines. I use them for training but then delete them once I'm up and running with 1940 subs.

Looks like you were right. I tested this and my results are:

That said, I don't know how you'd get the main Allied navy into deep ocean in the first place. I did it by console commands, but in my regular games they've been very cagey about having their bigger ships leaving their immediate shores apart from invasion support, and subs fare much worse in shallow waters:

 

[DGuller]

English Channel might not be representative. I usually stay out of sea zones likely to be bombed, and I would say that this is the one true counter to this sub zerg rush. In my game, I surrounded the three sea zones adjacent to Britain with my subs, but I stayed out of them until it was time to get naval superiority for invasion. English Channel in particular will always get bombed as soon as the Brits see subs there, and they may see them because they start with radars there.

As far as how I lure the big fleet out to be mauled, I don't know. I just set my subs on convoy raiding at Always Engage, and that drags in the escort ships, which in turn almost always drags in the strike force. I don't do anything special to lure the strike force, they seem to come out willingly often enough in all my games.

EDIT: Maybe it's less about bombers and more about the radars. I wonder if the land-based radars help detect subs more frequently during naval battles. They definitely detect subs for bombers to sink, but if they also help detect them during naval battles, then that is probably what limits them in the Channel more than anything. I guess the key ratio to maximize here is the damage delivered per chance of being spotted.

 

[bitmode]

EDIT: Maybe it's less about bombers and more about the radars. I wonder if the land-based radars help detect subs more frequently during naval battles. They definitely detect subs for bombers to sink, but if they also help detect them during naval battles, then that is probably what limits them in the Channel more than anything. I guess the key ratio to maximize here is the damage delivered per chance of being spotted.

You don't want to operate your subs in a Shallow Sea, like the Channel. It doubles visibility (https://hoi4.paradoxwikis.com/Strategic_region#Shallow_sea). Deep Sea like the coast of Portugal is ideal. I don't think radar has anything to do with it.

 

[DGuller]

You don't want to operate your subs in a Shallow Sea, like the Channel. It doubles visibility (https://hoi4.paradoxwikis.com/Strategic_region#Shallow_sea). Deep Sea like the coast of Portugal is ideal. I don't think radar has anything to do with it.

I see, I didn't know that. That said, mathematically speaking, how much of a malus it truly is depends on how often the subs get revealed from visibility as opposed to from firing a torpedo. If 90% of the time subs get revealed due to firing a torpedo, then even a whopping 100% shallow sea penalty would still be immaterial.

EDIT: Actually, never mind, sub visibility factors into torpedo reveal chance as well. Also, the active detection is a cubed function of sub visibility, so it seems like shallow seas would increase active detection part of it by a factor of 8. Sometimes I wonder whether the math needs to be this complex, I bet it doesn't help with balancing things.

 

[Shaka of Carthage]

Sometimes I wonder whether the math needs to be this complex,

Agree, True throughout most of their calculations. it seems overly complex for what it does.

 

[Sourlol]

Maybe you had all the upgrades while UK AI didn't even bother with the naval research.

Shouldn’t the historical UK ai be prioritizing naval tech—especially doctrines? If anything it’s second fiddle to air.and for that matter, shouldn’t the uk also prioritize her spy network? Surely the UK spies should know Hitler is building a lot of Uboats with snorkels and react accordingly with destroyers armed with anti submarine tech.

The AI isn’t very good at seeing the big picture yet (or ever?)...maybe the devs should get Deepmind to make an AI bot for HoI. Maybe in 500k iterations we may get a real game....or maybe it just learns 40w, loads of planes and roll.

 

[Zeprion]

Shouldn’t the historical UK ai be prioritizing naval tech—especially doctrines? If anything it’s second fiddle to air.and for that matter, shouldn’t the uk also prioritize her spy network? Surely the UK spies should know Hitler is building a lot of Uboats with snorkels and react accordingly with destroyers armed with anti submarine tech.

The AI isn’t very good at seeing the big picture yet (or ever?)...maybe the devs should get Deepmind to make an AI bot for HoI. Maybe in 500k iterations we may get a real game....or maybe it just learns 40w, loads of planes and roll.

In my opinion, the AI is fine the way it is. If you want a truly competitive game, play a multiplayer +20 players game. Singleplayer is mostly for roleplay.

 

[Gort11]

Man, I wonder what the UK could do by devoting all naval production to submarines.

 

[TheMeInTeam]

I was under the impression you could see '40 subs and kill with drop planes + radar + air superiority pretty easily, and once spotted destroyers or NAV can put them down.

Fighting '40 tech with '36 or interwar tech tends not to go well in general in the game. AI never does anything benefitting its fleet so it's doing the equivalent of sending interwar fighters into fighter 2's...while the latter also has doctrines.

 

[HugsAndSnuggles]

Man, I wonder what the UK could do by devoting all naval production to submarines.

Nothing worthy of praise, I'm sure. You see, the effectiveness of submarines is, basically, an edge-case for Germany: they have designer, default doctrine, proper admirals, even get a focus - everything to make a most-efficient (read: minimal visibility) 1940 subs as soon as possible. That said, even now (since nothing in naval battles was changed for a while) some people playing as Germany still experience their subs being useless - often, because they use subs in shallow waters around England, under heavy enemy air. What do you think UK will achieve with a fleet of subs, lacking dedicated designer and under suboptimal conditions (shallow waters and potential enemy air)?