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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.

Untitled.png


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.

uboateffort.png


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.

Sub Minelayer.png


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.

WolfPacks.png


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.

casualties.png


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.

Canada War Support.png


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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Sound good, but I still fear, that the best strategy will be to ignore all the naval stuff until late game, save your fuel and concentrate the research efforts on synthetic fuel, research, production, land and air warfare, unless maybe for a final naval invasion in the end game, when it is anyway already decided who wins.
The importance of commerce interdiction is heavily underrated so far.

reality --- hoi4

irl: convoy ships expensive.
hoi4: cheap

irl: Most convoy ships were needed during the whole war for import and export unless they were blocked like the Germans.
hoi4: very few needed for import in early and mid game, only in end game, but then it's often already decided and stopped.

irl: Lack of fuel and other raw materials due to allied blockade severely hampered axis war efforts. Only Germany produced a significant amount of synthetic oil, but still by far not enough.
hoi4: Synthetic oil and rubber can be made easily, and heavily increased by research. Steel is a resource, which can be produced out of nothing, not iron ore. So the axis powers hardly suffer from trade blocking, in contrast to reality.

irl: Most countries, especially insular states needed shipping and raw materials for their economy.
hoi4: The whole build-up of civ and mil factories is unaffected by naval warfare, since no raw materials are necessary.
 
We have speeded up research and tightened up ahead of time penalties to make it easier to research broad


kinda. you cant get the planes to strike, they are simply scouts improving spotting abilities for the sub

I do hope Japan somehow gets that option to allow their planes to strike, at least in late-game. The I-400 submarines were, after all, Admiral Yamamoto's idea to strike back after the Doolittle Raid in 1942.

Also, nice work on the DD, @YaBoy_Bobby. Submarine Warfare just got a LOT more interesting. :)
 
Are aircraft able to be used against subs in the new expansion? Historicaly they were very important.
 
Nice to see you here.

Good work.

But please be a little be more realistic.

According to Dönitz, an effective trade war required a target strength of the submarine weapon of about 300 boats. According to the doctrine of "one-third parity", one-third of the boats should be in front-line deployment, another third on approach and departure, and the last third for overhaul at home ports.

So you have let say 90 subs, so 1/3 in action 30, 1/3 in traveling & 1/3 at homeport.

You made the german subs far to strong .

The problem german wiki who contain this statement about 300 subs & much other info is not equal to the english wiki.


https://en.wikipedia.org/wiki/Karl_Dönitz

https://de.wikipedia.org/wiki/Karl_Dönitz#Zweiter_Weltkrieg (read 1.3.2 and translate to english)

-------------------------------------------------------

At moment germany has far, far, far, far to much ressources . In reality in year 1942 just 60% of steel for submarine production was avaiable. In HOI (if you play as german you have so much steel + occupied france that youre far far to strong. I dont like that.

Please , reduce the ressources . Thanks https://de.wikipedia.org/wiki/Karl_Dönitz#Zweiter_Weltkrieg

--------------------------------------------------------

In the 68 -month fight 781 of 820 German submarines (95.2 percent) were lost, 632 were demonstrably sunk by the Allies. Such a loss ratio had no other branch of service recorded, neither on German nor on Allied side. In fact he (Dönitz) was ugly leeader. At beginning he was good but turned more & more bad as long as the ww2 goes on. I hope you can do that in MTG, too . If you play near to historical. Thanks


Merry Christmas
 
Raiding and Reaving 1940 edition

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.

View attachment 428570

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.

View attachment 428585

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.

View attachment 428580

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.

View attachment 428583

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.

View attachment 428584

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.

View attachment 428586

By early ‘41 England 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 Russia.

See you all next week!

Rejected Titles:
-Raiding and Reaving, 1940 edition
-Subs, theyre not complete trash now!
-Under the sea, Darling its better

Welcome to the familly.

By the way... you really hyped me...

This is going to be the best DLC ever
 
Weren't the surface raiders a waste historically (outside of being a fleet in being the British had to think about)?

Well, the Scharnhorst and Gneisenau battleships did a very succesful raiding destroying or capturing more than 20 ships. And while the Operation Rheinübung ended in failure after the sinking of the Bismarck that battleship alone with the Prinz Eugen was big enough of a threat to the British that they deployed six battleships, at least two aircraft carriers and several destroyers to hunt them.

Of course, subs were far more effective in this assymetrical war since the Royal Navy was so superior in numbers compared with the Kriegsmarine, but I think that with fleets of equal numbers surface raiders can be quite dangerous.
 
Weren't the surface raiders a waste historically (outside of being a fleet in being the British had to think about)?

Not completely, less useful than a large submarine fleet would have been (however more versatile in being able to fulfil other roles), but some like the Graf Spee and the Admiral Scheer were pretty successful as surface raiders (and requires your enemy to divert resources into pretty beefy escorts).
 
@Secret Master as others have mentioned, the surface raiders were able to influence well beyond their effect because of the resources needed to hunt them down. Furthermore, the new technologies of huff-duff and radio made them easier (though not absolutely so) to track broadly. The resources needed to defeat the surface raiders required the assignment of significant surface forces, but those surface forces were also needed to protect the isles themselves.
 
@podcat I know this is off topic but I have a coupe of questions that weren’t answered in the previous two dev diaries (I think it was because I was too late to the party) 1. How will the Post-War peace go if you are very historical with the new borders (hoping for accuracy because I am a perfectionist and when playing the U.S.S.R. it bugs me that I can’t take the northern Königgsberg area and then give the south to Poland as well as the proper division of Austria but if your saving that for the next dlc which is rumored to have the U.S.S.R. in it which would be great then that is understandable)? 2. Will Winston Churchill and FDR be getting any new traits or portraits? 3. How many destroyers would you say is required to guard convoys in the three sea zone pattern? Also great dev diary and am definitely looking forward to the next one on submarines (and possible release date) and great dev diary @YaBoy_Bobby I am excited to choke Britain like Germany historically did.
 
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.
Plane catapults should:
-Decrease stealth (you know, being big fat box lobbed on top of the sub)
-Decrease maneuverability and speed (... big fat box, heavy airplane...)

I'm slightly confused, I can see that deploying the plane will help with detecting enemy, but it's not clear to me how will the plane itself not compromise submarine's position, both getting to air and landing???
 
So I guess important topic to this and overall naval combat is how refueling/rearming be handled, such as whether ships/subs can stay in position forever or what...
 
Sound good, but I still fear, that the best strategy will be to ignore all the naval stuff until late game, save your fuel and concentrate the research efforts on synthetic fuel, research, production, land and air warfare, unless maybe for a final naval invasion in the end game, when it is anyway already decided who wins.
The importance of commerce interdiction is heavily underrated so far.

reality --- hoi4

irl: convoy ships expensive.
hoi4: cheap

irl: Most convoy ships were needed during the whole war for import and export unless they were blocked like the Germans.
hoi4: very few needed for import in early and mid game, only in end game, but then it's often already decided and stopped.

irl: Lack of fuel and other raw materials due to allied blockade severely hampered axis war efforts. Only Germany produced a significant amount of synthetic oil, but still by far not enough.
hoi4: Synthetic oil and rubber can be made easily, and heavily increased by research. Steel is a resource, which can be produced out of nothing, not iron ore. So the axis powers hardly suffer from trade blocking, in contrast to reality.

irl: Most countries, especially insular states needed shipping and raw materials for their economy.
hoi4: The whole build-up of civ and mil factories is unaffected by naval warfare, since no raw materials are necessary.

One way to deal with some of these issues would be to implement the Civilian Factories mechanic for Convoys as well. The more civilian laws would use up a large percentage (30%? 50%?) of Convoys for Civilian Convoys. More militarized laws would reduce this, freeing up Convoys for strategic Resources, naval invasions, etc. The AI algorithm for spending PP would need to be adjusted somewhat, but IMHO it needs urgent attention anywhere as I keep seeing nations large and small that are hamstrung by spending their PP on generals and designers rather than laws.
 
Of course, subs were far more effective in this assymetrical war since the Royal Navy was so superior in numbers compared with the Kriegsmarine, but I think that with fleets of equal numbers surface raiders can be quite dangerous.

Not completely, less useful than a large submarine fleet would have been (however more versatile in being able to fulfil other roles), but some like the Graf Spee and the Admiral Scheer were pretty successful as surface raiders (and requires your enemy to divert resources into pretty beefy escorts).

The resources needed to defeat the surface raiders required the assignment of significant surface forces, but those surface forces were also needed to protect the isles themselves.

All of those points sound more like "The German surface raiders made a good fleet in being that required the British care about them" than "The German surface raiders were a wise investment for raiding convoys to defeat a superior naval power in a struggle on the ocean."

I bring it up, because I am always reminded of the Royal Navy's assessment of the merits of the Anglo-Germany Naval Treaty. The admiralty preferred a balanced German fleet (which is what the AGNA stipulated), because it could be beaten easier than a submarine fleet.

I've always contemplated how many u-boats Germany could have built and maintained for the cost of Bismark and Tirpitz. And how much further u-boat research could have gone before the war if research efforts had focused on u-boats instead of bigger battleships. I know Germany building up a large u-boat force would have provoked a harsher reaction from Britain (since they and France are the only real targets of such a navy), but I'm not sure the German surface fleet ended up justifying its cost during the war.