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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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This all sounds great and I'm excited to finally be able to conduct proper submarine warfare in HoI4! My concerns are, are submarines going to be too powerful (did they get buffed too much) and how well is the AI going to react to defending against an aggressive submarine campaign? Seeing the Canadian AI get smashed doesn't fill me with confidence.
 
Super excited to try out the new submarine system and all the cool stuff in Man the Guns.
P. S. Please for the love of God tell us the release date (or at least release date of the release date) so my agonizing soulbreaking anguish may end
 
We get to buy research speed for naval XP.
We have speeded up research and tightened up ahead of time penalties to make it easier to research broad

Seems that subs can equip planes now, can we design something like I-400? will it be covered in the following dev diaries?
kinda. you cant get the planes to strike, they are simply scouts improving spotting abilities for the sub
 
Oh wow, that seems incredibly powerful, looks like this will give Churchill a reason to fear the U-boat menace.

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.
Very interesting, previously even if you could cut the supply of resources, the navy and aircraft already deployed would not suffer a bit, and thus Sea Lion would still require you to build a very large surface navy.
Now, this really shows another strategic aspect of the fuel system. It is often stated how Germany will suffer with fuel, but with this (and perhaps ironically), this might actually give them a chance to fight Britain in the end, not to mention the WS penalty.
 
I would like to know this too

Okay that's pretty darn cool.

Super Atlantic raiding fleets is only getting better.

I noticed that there was mention of special sub hulls for the Germans, will this also be true for the Japanese I400 or will they be part of the ship designer, i.e bombing craft/scout craft for non-german submarines?
 
Welcome to forum writing, @YaBoy_Bobby! :) This is an important part of the game and it's good to see you've moved it forward. The interaction between convoy raiding and War Support is a good use of this new mechanic. Will it require MTG or will it be in the Ironclad patch?

Will the AI react to convoy loss and start developing an anti-submarine component? o_O

This is a very important question. So is the mirror question: will certain powers always follow a submarine strategy (doctrines + techs + production) in SP or will the AI vary its strategy from game to game?
 
Very nice changes to subs, playing Germany have become a lot more fun now.

Now, how much can the United Kingdom and Canada protect themselves with a modern destroyer fleet and a really big merchant fleet? Because while I know numbers are not final losing nearly 30% of war support because of commerce raiding seems quite a blow.
 
@YaBoy_Bobby welcome to the Hoi family! I hope to see lots of good things in the future! Also a question for anyone on the team, with all these new uses for naval xp, could we see a buff to xp gain? Or do we get blueprints for some of these more specialized subs. It seems silly to think that germany has to go convoy raiding for 1 or 2 years before they realize "oh, what if we just mined the channel" when they had already planned to do that prewar.
 
Obviously for convoy raiding the focus is subs, but is it worthwhile to try and surface raid (as the Germans did historically), or will it just waste your ships?
 
True, but Doenitz estimated he would need something like 700 U-boats to pull off such a thing, especially given that only 30% or so were operational at any given time. Anyway, we're just spit-balling. ;-)

Where the hell are you getting those numbers? Thats like 2.5 the amount Donitz said he wanted which is 300.
 
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
Oh yes, and one question, will you have any info on how you enemies' fuel stockpile is doing?
This is all and well as a strategy, but if you can only truly know if it is actually working at all is when you start operation Sea Lion and it either goes all well or horribly wrong (and you lose your entire fleet and a whole army in the process), I figure it would still seem like a lot of guesswork would be needed.
 
but is it worthwhile to try and surface raid (as the Germans did historically), or will it just waste your ships?

Weren't the surface raiders a waste historically (outside of being a fleet in being the British had to think about)?