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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.

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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German cruiser submarines are all well and good, but will the French be able to build submarine cruisers?

Not only France but almost all the major nations had different pre-war models of these large sub.

They already stated that they will not. There would be no point in this at all other than as a gag ship for silly playthroughs by youtubers like ISP.

Did you refer to subs with guns or to the large cruiser submarine in general ?
 
Could you please define 'tightened up'. Were ahead of time research bonuses increased or decreased in severity?

There was a DD about it back in October https://forum.paradoxplaza.com/foru...ary-amphibious-vehicles-and-research.1122205/

Basically ahead of time bonuses are in the form of 'X months off' not 'Y% off' (so fighter 3 might be considered a 1943 tech as opposed to a 44 tech). Also bonuses are altered so they are multiplicative instead of additive (so no more 1 day researches if you get enough bonuses). Oh and you can spend xp to speed (selected) things up - army xp for doctrines, naval xp for ship components
 
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

So you are saying to us that we can build the I400 class but they will not be able to attack with planes right?
This means that they will be able to operate in almost any place in the world with its 37500 nm range right?
Their planes were not the only special characteristic of this submarine.

IJN had many interesting ships that were not well employed due to lack of technology in other areas like radar, description, radio and other. In a modern warfare it is useless to have a great naval engineering and bad communication capabilities and things like that, but in the game, it would be interesting to be able to use those unique ships since in the game even Albania can build and use effectively jet fighter for example.

In my opinion, CVBBs and CVSS should be implemented in the game with the limitation that they will be limited to do just one attack with aircraft per battle and the decision to research them and to make a downgrade to their ships in exchange for just some more aircraft in battle should be left for the player to decide.
 
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That depends. Historically a tactic sometimes attempted by submarines when attacking a convoy was to try and ambush the escort destroyer first, before the DDE were actively hunting for them ( because once they were aware of a uboat threat they were almost impossible to hit due to speed and maneuvering ). This was not as easy as hitting a freighter but could still pay off because it made future attacks much easier.

If I remember correctly the German submarines sank about 40 or so allied destroyers during WW2, so it would be a shame if it wasn't possible to sink DDs with submarines at all. A stray torpedo intended for another target had enough explosive force to often split a destroyer in half.


Ofcourse I agree that the current situation where submarines only fire on destroyers if they are present due to them rushing forward first is very silly, but it seems like this has been fixed if you read last weeks DD about naval combat.
I undestand your words Alex but combat target selection in all the combat system of game is random, and the original post were pointing that is posible if a 20 convoys and 5 scorts, they first try to engage 3 dd until a convoy or in other world do it with no a minimal rational planning, and more important i dont see subs gooing deep and getting hard to detect in a sub scape phase.

This particulary post dont like me much, all the things mentioned are really correction of actually bug no a new feature.

More important is how the scorts works, they should be assignated to the routes and no a "zonal potrol of convoys". Darkest Hour convoy raiding would be no very deep, sure its no the best, but DD as patrol work as patrol, DD as scorts works as scorts.
 
Well I mean, that’s kinda the point, no?

Irl Germany couldn’t bring herself to prioritize this aspect of warfare, so should be the case for the player, unless their strategy differs from historical germany.

At least today, with these changes a submarine strat become viable. Previously it was never a choice never a decision.

I like that no country can do everything, that choice are made and sacrifices realized.

I my mind, you wouldn't progess the Trade Interdiction path very fast just in it self. But when you research modern Subs, built alot of them, and sink alot of Convoys with them, then you automatically progess rather fast trough the Trade Interdiction path, without having to sacrfice a research slot to research these doctrines in peace time, which is also a bit weird to do in general.

So if you go ahistoric and don't built any Subs you don't progess in the tree, besides maybe 1~2 Doctrines in the whole war, if you build Subs to historical numbers, you get quite far, and if you go ahistorical and build hundreds of modern subs and starve Canada and UK down, you also get very fast Trade Interdiction doctrines.

Still a decision to be made
 
combat target selection in all the combat system of game is random, and the original post were pointing that is posible if a 20 convoys and 5 scorts, they first try to engage 3 dd until a convoy or in other world do it with no a minimal rational planning, and more important i dont see subs gooing deep and getting hard to detect in a sub scape phase.

Last weeks dev diary:
https://forum.paradoxplaza.com/forum/index.php?threads/hoi4-dev-diary-new-naval-combat.1133625/

What it says about subs:

To deal with distance and screening issues we have split up the battle in 4 areas per side to represent position and distances.

...

Submarines - Under the sea. This area is actually two as we separate located submarines (which can be engaged with depth charges) from unlocated submarines.

By splitting things up in discrete distances unlike the old system we can more easily capture the impact of distance and positioning, and keep it easier to see what is going on at a glance.

...

Torpedoes - These are the big capital killers. They ignore armor, and have big damage but are terrible at hitting fast/small ships. Torpedoes can hit any line as long as it is not screened properly. So if your screening is down to 50% then half of the enemy torpedoes can be fired at your battle line, and if the battle line is also weak some torpedoes can slip through and hit carriers or convoys.

...

Depth Charges - This is the only weapon that can hurt subs, and it only works versus revealed subs.
Carrier Planes - Carriers can carry different kind of planes. Naval and dive bombers help attack other ships and fighters help protect yourself. The whole air model in naval combats is now more in line with the rest of the game and takes place in the airzone as you would expect. So can now be disrupted etc. This fixed a bunch of issues we had with the interaction between land based air and carriers.

...

Whenever ships are called to a combat, they will take an organization hit, which slows down their joining. Similar delays also apply for missions like convoy raiding or escort at suboptimal efficiency so it’s harder to bring all your power to bear at the same time.

On the flip side, if you take out the enemy side before the incoming ships arrive, the battle ends and you can run away (or the sides have to re-spot each other if they still want to fight), the idea is to help subs and other raiders out by allowing fast hit-and-run battles.

...

This is also where submarines come in. They follow normal torpedo rules, but also free to circumvent them when it comes to escaping ships. So if you have subs hiding in your battle they can engage the enemy capitals as they start to run (of course this reveals them, depending on doctrine levels, leaving them open to return fire from anti-sub vessels).
 
If I remember correctly the German submarines sank about 40 or so allied destroyers during WW2, so it would be a shame if it wasn't possible to sink DDs with submarines at all. A stray torpedo intended for another target had enough explosive force to often split a destroyer in half.


Ofcourse I agree that the current situation where submarines only fire on destroyers if they are present due to them rushing forward first is very silly, but it seems like this has been fixed if you read last weeks DD about naval combat.
Subs can definitely sink DDs now. I am looking forward to seeing how this will play out and if the AI can handle the decisions, or at least be scripted, to be a worthy opponent at sea.
 
Will be able to manual set up trade routes? and maybe get large convois instead of many small ones? then the player have the ability to guard the atlantic,get 50 oil instead of the 20 needed and has still 30 in reserve instead of risking his convois every month. the same can be done with lend lease as well (small number per month or 1 big shipment with many convois)

also to drew manual traiding routes prevent the soviet union sending convois into the baltic sea when at war with germany, because the ai does that as long as germany dont kill denmark. so your concois go and die there like lemmings
https://forum.paradoxplaza.com/forum/index.php?threads/hoi4-dev-diary-naval-access.1114924/

If you read through the previous dev diaries you will find that your questions were answered in August. You will be able to designate sea zones as dangerous which will make convoys reroute around them, and will shut down trade if there are no alternative routes.
 
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. ;-)
NORTRASHIP made a significant difference, too. Hoping to see it included when the Norse get our focus trees.
 
i have read it but it doesnt talk about targering from sub, if its no balanced its very probale that you sunk scorts with low ratio of convoys as dont drop supply line.

It talks about targeting for torpedoes. Convoys go in the back row (along with carriers), torpedoes have a chance to ignore forward rows depending on level of coverage provided. They also say 4 front row cover 1 of the row behind so unless the convoy country has 4 light ships per convoy then the chances are torpedoes will hit convoy ships.

There is a 50/50 chance per torpedo salvo the sub is spotted (modified by doctrines)
 
so naval bombers can now be used to attack convoys?
 
Like the changes to sub warfare. As a Canadian player I see flooding the Atlantic with destroyers and the Pacific with subs.
Query: Will there be a pink submarine badge for sinking a truck?