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HoI4 Dev Diary - Subs and Convoy Raiding

Greetings, I am a game designer new to the HoI4 team. This is my first dev diary, so be gentle ;). Also, sorry for the late post today. I am an American and when it comes to WW2, we show up late.

Today’s diary entry covers our improvements to submarine convoy raiding. In past versions of HoI4, submarines have not really pulled their weight. We have sought to change that and make them worthwhile to build. I recently put these changes to the test by playing a Germany campaign.

My naval plan as Germany was to exploit the central Atlantic and Cap Verde Plain with a submarine wall. This would hopefully prevent England from getting necessary resources from the USA and the colonies. The biggest effect of this resource shortage would be the UK running out of fuel, crippling both their navy and air force. This would hopefully open the UK to sea lioning before the USA joins the war or at the very least, make winning the air war very easy and cause permanent damage to the UK’s fleet.

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We have previously mentioned the spotting system, and how naval task forces are revealed over time. This functions a little bit differently for subs. Spotting an enemy sub outside of combat is based upon chance. The chance for this to happen is based on how quickly the spotter will spot their target. However, it is possible for a submarine to have a large enough advantage in spotting that the submarine task force will not be able to be spotted. However, convoy escorts will still be able to fight against submarines once combat is initiated, even if subs are not normally detectable by enemy taskforces on the map.

This system creates a tech race between sub stealth and sub spotting, with subs having a better chance of getting an advantage in the early game. Previously, submarines would eventually be detected and killed no matter how good at hiding they were. This is no longer an inevitability.

Before beginning the war, I made sure to complete the German naval focus line down to “U-boat Effort.” Along with getting a research speed boost and some dockyards, the focus gives Germany access to a “Cruiser Submarine.” This sub is a sort of tech 2.5 Sub with extended range, some unique module options, including catapult planes, and the ability to be upgraded with a snorkel.

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Part of my plan for giving England a hard time included mining up the English Channel. I executed this plan with a cruiser sub equipped with naval mines and plane catapults. These plane catapults boost the sub’s surface detection, giving them an advantage in being detected and helping them remain invisible, at least for the first couple years of the war.

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I made a tech 3 sub-variant for minelaying the Eastern North Sea and a tech 3 raider-sub for Cap Verde Plain. When I demanded Danzig from Poland in August of ‘39 I had 79 Subs of various roles ready and much of the Trade Interdiction doctrine complete. This focus on raiding will give my subs a further detection advantage over other countries that have yet to complete their convoy escort doctrines.

Speaking of the naval doctrines, we have made some changes all around to account for the new combat system and apply a bit of balance. In particular, we have given some buffs to the Trade Interdiction doctrine to make it more attractive than it was previously. We have added additional survivability for submarines and more of an edge in surface detection values. Capital ships have received some defensive increases as well.

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Torpedo reveal chance is a new thing for subs. When subs are in combat, attacking no longer guarantees that a sub will reveal itself. Baseline, subs have a 50% chance to reveal themselves when launching a torpedo volley. This can further be improved through doctrines and admiral traits. This makes ambushing protected convoys safer and retreating when too many destroyers show up easier.

In my campaign, I capitulated France in early December of ‘39. To help with the Axis’s naval situation I formed Vichy France. Before France fell they had been contesting my raiding of Cap Verde Plain to the best of their ability, but I was still seeing some success. Forming Vichy France put more ships in the hands of the Axis and would further help to stretch the limits of what England could endure at sea.

With Vichy France on my side, early 1940 saw a massive spike in convoys raided as Cap Verde Plain and the Mid-Atlantic were now completely covered. By this point, I had ~20 dockyards producing subs for minelaying and raiding. All of my newest tech 3 Raiders were seeing great success in under the guidance of Karl Dönitz. Even when contested by British convoy escorts, they were able to get a respectable amount of kills and retreat. Naval bombers were also ramping up operations in the English channel.

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We have added a new effect to convoy raiding, war support reduction due to raiding. By mid-1940, Canada had been raided to 0 convoys and had their war support reduced to a point where they were no longer able to support War Economy. This helps to promote raiding and discourages blunt forcing convoys through an area where you are being raided.

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By early ‘41 the UK had been choked out of convoys and fuel and was unable to keep their navy running and were about open to a naval invasion. By mid ‘41 I had naval invaded the UK and was Setup for an attack on The USSR.

See you all next week!

Rejected Titles:
-Raiding and Reaving, 1940 edition
-Subs, they're not complete trash now!
-Under the sea, Darling its better
 
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Is there going to be an easier way to identify which ships you've lost? I might be missing something in the current version but whenever I lose ships and I'm trying to replace them, it can be a pain. With all these new variants, this could become an even bigger problem.
It'd be nice to get a summary of what ships have been lost from each fleet during battles and potentially a way to auto rebuild them or set off a replacement to be built (if you can afford it or want to)
 
Is there going to be an easier way to identify which ships you've lost? I might be missing something in the current version but whenever I lose ships and I'm trying to replace them, it can be a pain. With all these new variants, this could become an even bigger problem.
It'd be nice to get a summary of what ships have been lost from each fleet during battles and potentially a way to auto rebuild them or set off a replacement to be built (if you can afford it or want to)

They have talked about reserve fleets for each theatre so as long as you keep those stocked with each type you should be okay. It's not the best method but it should work.
 
Maybe something like the new fleet manager from Stellaris? I'm still trying to get my head around it but having a way to create different fleet templates would help. Though WW2 ships were moved around and changed role a lot during the war.
 
Maybe something like the new fleet manager from Stellaris? I'm still trying to get my head around it but having a way to create different fleet templates would help. Though WW2 ships were moved around and changed role a lot during the war.
This is a brilliant idea. I hate having to tinker around with 'refilling' fleets with lost ships. The Stellaris style Fleet Manager -- and being able to prioritize which fleets receive replacements -- would be a perfect way to help solve the issue and take away some tedious micromanagement which has no direct impact on the game.
 
This is a brilliant idea. I hate having to tinker around with 'refilling' fleets with lost ships. The Stellaris style Fleet Manager -- and being able to prioritize which fleets receive replacements -- would be a perfect way to help solve the issue and take away some tedious micromanagement which has no direct impact on the game.
Since we have a global queue for production it could even enqueue missing ships or indicated deficits in the production menu.
 
We actually do.

https://en.wikipedia.org/wiki/I-400-class_submarine
"Cost: 28,861,000 JPY in 1942"

Cost of Japanese Carriers:
https://web.archive.org/web/2008040.../navydata/cno/n87/history/wwii-campaigns.html
"3895 Yen/ton" so a 26000 ton Shokaku would be estimated at 101,270,000 JPY

28.86 million / 101.27 million = 28.5% the cost of a Japanese fleet Carrier.
Estimating costs in command economies is famously hard, those numbers could be off by an order of magnitude. Without good statistics on man-hours of different occupations (and quantities of limited resources) you can't really compare them.
 
Estimating costs in command economies is famously hard, those numbers could be off by an order of magnitude. Without good statistics on man-hours of different occupations (and quantities of limited resources) you can't really compare them.

Under what assumption do you draw the conclusions that the man-hour cost of the same dockyard workers building different kinds of naval combat vessels can be wildly different and off by as much as an order of magnitude?

I am asking because when people say that cost estimation is hard in command economies they normally mean the costs in comparison with other nations or currencies, not within the same currency, nation, and even within the same profession!
 
Under what assumption do you draw the conclusions that the man-hour cost of the same dockyard workers building different kinds of naval combat vessels can be wildly different and off by as much as an order of magnitude?

I am asking because when people say that cost estimation is hard in command economies they normally mean the costs in comparison with other nations or currencies, not within the same currency, nation, and even within the same profession!
I think you must have misread the sentence as I have stated no such conclusion. To restate my point: Yen values are largely meaningless and a sensible comparison would have to be made on the basis of man-hour numbers after normalization (accounting for differences in methodologies, should they have been measured/estimated independently for the compared objects) and/or quantities of limited resources.
 
I think you must have misread the sentence as I have stated no such conclusion. To restate my point: Yen values are largely meaningless and a sensible comparison would have to be made on the basis of man-hour numbers after normalization (accounting for differences in methodologies, should they have been measured/estimated independently for the compared objects) and/or quantities of limited resources.

To restate my point: Most Historians claiming Yen or Reichsmark values are largely meaningless for comparison mean when used in comparison to other currencies or over larger periods with inflation like comparing 1933 RM to 1943 RM, not Yen in comparison to Yen within the same business and within roughly the same period of the war.

The biggest error in comparing war material costs for Japan or Germany within the same country normally is if the cost includes fully kitted out with weapon-systems and other auxiliary systems or not, which can be a difference of +-20% or even slightly more ( in extreme examples were tank prices are given without engine ), but not an order of magnitude error.
 
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To restate my point: Most Historians claiming Yen or Reichsmark values are largely meaningless for comparison mean when used in comparison to other currencies or over larger periods with inflation like comparing 1933 RM to 1943 RM, not Yen in comparison to Yen within the same business and within roughly the same period of the war.

The biggest error in comparing war material costs for Japan or Germany within the same country normally is if the cost includes fully kitted out with weapon-systems and other auxiliary systems or not, which can be a difference of +-20% or even slightly more ( in extreme examples were tank prices are given without engine ), but not an order of magnitude error.
The ships in question (Shoukaku and I-400) were built by different "companies" (arsenals) and funds were likely authorized by different people (or rather chains of people). More importantly the contracted/estimated prices often do not reflect costs in limited resources (which were mostly state controlled and allocated separately), even in cases when they were the real limiting factor and could potentially dwarf other components in price, should they be market-allocated. Fiat money amounts are a really bad measure of costs in this setting, as it is not a limited resource.

That of course doesn't change the fact that Shoukaku-class ships were far more cost-effective than gigantic subs.
 
That of course doesn't change the fact that Shoukaku-class ships were far more cost-effective than gigantic subs.

That sounds very unlikely. The normal rule of thumb is that the more ships of a type that are built, the more cost-effective the construction can be due to economies of scale, and Japan built both more I-400s then they built Shokakus as well as more Submarines that were floatplane capable than they built Carriers.

None of this has anything to do with subs and convoy raiding anymore though, so I don't see any point in continuing in this thread. If you want to continue this argument over how many I-400s a Carrier was worth, first state your own standpoint and present your sources/facts to back it up, and preferably either in a new thread or PM me instead.
 
Little late to this diary, but reading through, it does seem to hold potential for adding a more plausible dimension to the game. Obviously, the proof is in the pudding, so we won't know for sure 'til we get our grubby little paws on it, but I certainly hope this brings much needed life to the battle of the Atlantic.
 
I think why I would not support 'carrier subs' is that their capabilities are so miniscule.
They carry 3 (!) planes and very limited ammunition (four torpedoes, three 800 kg bombs, 12 250 kg bombs) and fuel.
It is more a 'commando' weapon but in terms of impact on the scale HoI4 simulates it it is rather better fitted by using a decision even rather than the actual boats.
I think this capures the real capabilities of the I-400 class pretty well, and I think it could feed into an interesting future expansion/dlc, too. Commando attacks and guerilla warfare became an increasingly important part of the strategy of some nations as WW2 progressed; the "raid-strike" capability of various systems and doctrines is something that could be fun to expand upon - British commando raiders and SOE, Italian (and British, and later German) mini- and micro-submarines and the Japanese I-400 "carrier submarines" all strike me as options to cover under such an expansion, but I don't think any of them fit well into the standard combat system as currently constituted. Maybe add a new type of mission, with "commando raid" appropriate outcomes and parameters to be accessed by all these types of unit? An expansion covering these types of unit, plus coverage of resistance/guerilla type operations in occupied lands, is something I could see working very well, if done "right".

PS - sorry if a bit rambly - just got back from a trip to the other side of the world, and still a bit jetlaggy...
 
I think this capures the real capabilities of the I-400 class pretty well, and I think it could feed into an interesting future expansion/dlc, too. Commando attacks and guerilla warfare became an increasingly important part of the strategy of some nations as WW2 progressed; the "raid-strike" capability of various systems and doctrines is something that could be fun to expand upon - British commando raiders and SOE, Italian (and British, and later German) mini- and micro-submarines and the Japanese I-400 "carrier submarines" all strike me as options to cover under such an expansion, but I don't think any of them fit well into the standard combat system as currently constituted. Maybe add a new type of mission, with "commando raid" appropriate outcomes and parameters to be accessed by all these types of unit? An expansion covering these types of unit, plus coverage of resistance/guerilla type operations in occupied lands, is something I could see working very well, if done "right".

PS - sorry if a bit rambly - just got back from a trip to the other side of the world, and still a bit jetlaggy...

It's a fair comment. Weird edge-case stuff like the I-400 are probably best handled through decisions and events. Stuff like, "Our commandoes think they can raid this airbase, proceed?" where you risk equipment and manpower for the chance to damage the airbase and the planes in it, with success being more likely with better special forces and encryption/decryption tech, and failure being more likely with better enemy encryption/decryption and military police techs.

The I-400 could be part of a naval equivalent to that sort of thing.
 
It's a fair comment. Weird edge-case stuff like the I-400 are probably best handled through decisions and events. Stuff like, "Our commandoes think they can raid this airbase, proceed?" where you risk equipment and manpower for the chance to damage the airbase and the planes in it, with success being more likely with better special forces and encryption/decryption tech, and failure being more likely with better enemy encryption/decryption and military police techs.
Decisions and events could be set up to handle something now, but I was thinking really in terms of something more dedicated; maybe it would work like this:

- Select a desired target; this could be an airbase, a port, a specific ship or other military asset, infrastructure in a state (basically any state building might be a good target).

- Allocate special forces and/or other assets to the target.

- Find out the results after a suitable delay.

Maybe this would work a bit like the air and naval systems: allocate special forces/assets to a target region/state, select a mission type and leave them to operate until reassigned.