Are submarines overpowered? A quick test on the effectiveness of U-boats

[KDEstroy]

I built 64 submarines for Germany, using this template:

This is basically the ultimate template. All submarine and torpedo techs are maxed out. All submarine-related doctrines in Trade Interdiction are researched. No other modifiers from national spirits, design companies or high command.

I build 29 DD's and 2 escort CVs for France:

A specialized hunter-killer destroyer, with a pinch of torpedoes. The CV was just 1936 carrier with capacity for 40 planes, and radar. All convoy escort doctrines in Fleet-in-being were taken.

I split the subs into 8 packs of 8, and set them to raid the Iberian Coast, a deep ocean region, which buffs subs and nerfs DDs. I split the French escorts into 6 fleets, 2 of them with a carrier, and set them to patrol. Both fleets set to engage at high risk, and never repair. France started trading with the US to populate the seas with convoys. The wolf pack went raiding for about 4 months. Results:

In total, the subs sank about 75 convoys, for a loss of 31 subs. The French lost 15 DDs.

Now, this is interesting, because the IC loss ratio is actually slightly in favor of Team U-boats: France lost 35535 IC vs German losses of 34410. And by interesting, I mean absolutely broken. A dedicated combined arms hunter-killer task force made up of specialized ASW destroyers and aircraft carriers should not be losing a war of attrition to submarines, no matter how advanced they are.

However, there is one minor catch: 5 surviving U-boats were actually down to 15% health, while all the escorts were full health. If you factor in the repair cost, France would be winning. But ships maintain their XP level after being repaired, so there's that. The French DDs were also a little more expensive than they could be.

TL;DR Just spam Sub 4's with snorkels, even if your enemy builds a dedicated ASW fleet to hunt you down, it's an even fight, you'll inflict as many losses as you take.

 

[HugsAndSnuggles]

Now, this is interesting, because the IC loss ratio is actually slightly in favor of Team U-boats: France lost 35535 IC vs German losses of 34410. And by interesting, I mean absolutely broken. A dedicated combined arms hunter-killer task force made up of specialized ASW destroyers and aircraft carriers should not be losing a war of attrition to submarines, no matter how advanced they are.

I think, part of the reason is your destroyer design: for ASW 2 depth charges are, usually, enough to one-shot a same-year-tech sub (provided you have good enough admiral to offset deep ocean penalty). I'd also drop torps, gun and AA: fighting surface ships (or planes) is not their job; if anything, it inflates their attack score (not to mention, cost) making them more likely to engage enemy surface fleets (something you should have a strike force for).

For a dedicated ASW task force it's best to use tier 1 or 2 destroyers with coastal defence designer, which makes them comparable to submarines in production cost (although, it comes with an added requirement of better naval base coverage). Not sure if CVLs are worth it, simply because of fuel costs, but if you can afford it, they do a better than old CLs under that doctrine (even refitted for ASW).

 

[Secret Master]

I split the subs into 8 packs of 8

This is not sufficient.

In a real war, you want more coverage of the ocean, so you want to set up 10 task forces of 3 under each admiral. This is vital to a proper submarine campaign, because when you try to sink Britain's merchant marine, they might have 10+ different routes going through a sea zone. A task force of 8 subs can only engage 1 convoy route at a time. With smaller groups, you can have more subs engage more convoy routes simultaneously. Since ships can only be in one battle at a time, the warships can be in 1 battle while 9 other convoy battles are being fought elsewhere.

But wait, there's more!

A maritime power like Britain probably also has additional convoy routes going through other zones. So, with more submarines spread out in the fashion I describe, you can effectively hit 100% of all possible routes heading to Britain without 60 submarines. With them divided up properly, you have the potential to literally drag every single convoy route into combat at the same time (actual results will vary, of course). That also doesn't begin to address various allies buying English stuff and hitting their convoys, too.

That's not all, though.

When testing submarine effectiveness, you absolutely must test admirals and doctrines. The raw stats on submarines are powerful, but until you put them under Donitz with the right traits and the right branch of Trade Interdiction, you don't see just how powerful submarines can really be. In some situations, Torpedo Reveal Chance has a bigger impact on convoy battles with escorts present than the visibility of the submarines in general. All the stealth in the world doesn't matter if your subs reveal themselves via torpedo fire constantly.

 

[Vlad123]

If i spam old submarine but with modern torpedos and engine?

 

[Sbrubbles]

If i spam old submarine but with modern torpedos and engine?

New subs have much lower sub visibility (never mind other stats like hp, speed and reliability), so I would assume it isn't worth the discount.

 

[Vlad123]

New subs have much lower sub visibility (never mind other stats like hp, speed and reliability), so I would assume it isn't worth the discount.

The crusader sub are good?

 

[KDEstroy]

This is not sufficient.

In a real war, you want more coverage of the ocean, so you want to set up 10 task forces of 3 under each admiral. This is vital to a proper submarine campaign, because when you try to sink Britain's merchant marine, they might have 10+ different routes going through a sea zone. A task force of 8 subs can only engage 1 convoy route at a time. With smaller groups, you can have more subs engage more convoy routes simultaneously. Since ships can only be in one battle at a time, the warships can be in 1 battle while 9 other convoy battles are being fought elsewhere.

But wait, there's more!

A maritime power like Britain probably also has additional convoy routes going through other zones. So, with more submarines spread out in the fashion I describe, you can effectively hit 100% of all possible routes heading to Britain without 60 submarines. With them divided up properly, you have the potential to literally drag every single convoy route into combat at the same time (actual results will vary, of course). That also doesn't begin to address various allies buying English stuff and hitting their convoys, too.

That's not all, though.

When testing submarine effectiveness, you absolutely must test admirals and doctrines. The raw stats on submarines are powerful, but until you put them under Donitz with the right traits and the right branch of Trade Interdiction, you don't see just how powerful submarines can really be. In some situations, Torpedo Reveal Chance has a bigger impact on convoy battles with escorts present than the visibility of the submarines in general. All the stealth in the world doesn't matter if your subs reveal themselves via torpedo fire constantly.

I've researched all submarine doctrines in Trade Interdiction, and put Donitz in charge of the U-boat fleet.

 

[Secret Master]

I've researched all submarine doctrines in Trade Interdiction, and put Donitz in charge of the U-boat fleet.

Did you give Donitz all applicable traits to which he is entitled? He can start with several that make him a superstar before the war even starts.

 

[Putuna]

The amount of research/IC you have to build to counter subs is much higher then the IC/research you need to spam them. It's very frustrating really since it was really the exact opposite in history. Also I feel like your ASW fleets are little silly as their is no way you would be able to spam enough CVL to actually have meaningful numbers of those.

 

[Edungeon]

All on patrol? Shoudnt you have some of the fleet on Escort and after 100% the rest on patrol?

 

[goodcigar]

Why did you do Patrol and not Convoy Escort? I also don't understand how you are supposed to know how big to make your Task Forces. The game does not explain at all.

 

[brainiac1530]

Not because that's generally the best idea, but purely for the purposes of this test. If your goal is to sink subs, patrol is how you're going to do it. You have to catch them on the defensive so that they're revealed and you can attack them. Escort fleets are always on the defensive, so the only way you'll get to attack the enemy subs in a battle which started from an escort is if they're revealed by firing torpedos (or, at what's usually a low probability, randomly detected.)

In a real game, you'll want to have both escorts and patrols, with ships best suited to each task. Many of the major nations that need to do a lot of escorts (US, UK) start with plenty of old model DDs you can use as escorts, and you can build more during the early years -- it's one of the better things to use your dockyards for at that time.

There probably isn't a "correct" task force size. However, the AI seems to be quite fond of a 6DD / 2CL task force (for patrols?), so you can probably design some task forces to exploit that composition. In general, you should try to strike a balance between covering the areas that need to be covered and having larger task forces which can fight better in the initial confrontation. The real exception is strike forces, which can really just be one big dumb deathball. Patrols can also often be a single ship with very high detection values -- a cheap way to have a task force with a very high average for faster detection.