Hearts of Iron IV News

If you missed the previous Dev Corner, make sure to check it out here.


Briefing: Thermodynamics
Author: Zwirbaum


Hello everyone!

It has been eight days since the last dev corner, which means it is time for another one. Last time, I was talking about some of the new naval concepts and changes coming to the Hearts of Iron IV. Today I will be talking about the introduction of Coal and Energy into the game. As a casual reminder keep in mind that everything discussed here is in a relatively early stage, and as such is subject to change.I also want to add that not every dev corner will be a long one, and some may end up on a rather short side. But without further ado, let’s keep this lump of coal rolling.

For the first time since the launch of the game we will be adding a new resource to the game, as every other resource, Steel, Rubber, Tungsten, Chromium, Aluminium and Oil were since day 1 in-game (with Oil getting Facelift in Man the Guns to be used for Fuel production instead of equipment production). This resource is Coal - to put it very briefly it will be serving as a ‘fuel’ in the form of Energy for your industry to keep it running efficiently.

[h3]Core Concept[/h3]
What are some of the goals when it comes to adding Coal & Energy, and what do we want to achieve with it?

• We want to introduce a potential soft-limit on the current almost limitless industrial expansion.
  
• Increase importance on expanding and securing a resource base for your needs.
  
• Provide a bit more interesting choices when it comes to economic laws, give some incentive for a player to consider ‘demobilize’ at some point during the gameplay, and that War Economy / Total Mobilization is not always the one and the only one right choice.
  
• We are not aiming at creating a super complicated or overly complex system for energy/economy model
  

What is all the fuse about? Sardinia starts with 2 units of Coal at the beginning of the game. As usual, numbers are subject to change, so please do not despair yet.

[h3]Base Concept[/h3]
So the system works like this: Coal is excavated just like every other resource in-game. Each unit of Coal that you have for your own use (so not traded away) will produce a set amount of Energy, which then in turn is used to power up your industry - your civilian, military factories and naval dockyards, which for the ease I’ll be later calling them in this dev corner as ‘factory’. Each Factory, regardless of the type, has the same base Energy demand, so what you are seeing in the top bar as your industry size should also give you a very rough estimate of the demand.

This totally mysterious country, that is totally unrelated to Sardinia from the previous screenshot starts with 56 factories, and now has a mysterious bar under the factory count.

[h3]Economy of the Scale[/h3]
However the base Energy demand is not everything, as each Factory you own will also introduce a little extra scaling cost to the demand per factory, so a small, undeveloped minor country will be able to sustain their few factories with a rather small amount of coal, while historically accurate Luxembourg spanning across Eurasia will require much more energy in order to effectively satisfy the ever hungry maw of their Industry.

[h3]Lower Mobilization Law is your Friend?[/h3]
Most, if not all, economic laws will also have factory energy consumption modifiers, which will essentially either increase or decrease how much each factory (including the ‘scaled’ portion from ‘size’ of the industry) will demand energy. Higher mobilization laws will have higher energy demand, to represent longer working hours, more shifts etc.

Economy Law picker will also now proudly display the energy consumption modifier at the first glance, so that you do not need to scour through the tooltip to find the modifier. Before you start going crazy with guessing what is the second number, it is just the expected amount of consumer goods - the icon is currently placeholderish, as we haven’t adjusted the previous icon yet.

[h3]How does it work though?[/h3]
I will start with a quick reminder how the Civilian, Naval and Military Industry operate in-game currently. Essentially each of the ‘factories’ have a specific base amount of output valued in points that they contribute daily to. (5, 2.5 and 4.5 respectively). And that was further modified by all the technologies, laws, ideas, ministers, national spirits with various ‘Construction Speed’ or ‘Dockyard/Factory outputs’ modifiers. I am not mentioning Production Efficiency, as that was unique to the Military Factories.

So how will that operate in the brave new world? We will now have a base output for each of the industry types - which means that regardless of the energy, you will always have at least this much output from your factories. And there will be ‘fully powered’ output values for the industry. Depending on the energy ratio you are providing, you will end up somewhere on that scale, e.g. If you have 50% energy - you will be getting output that is ‘50%’ way from the base output to the fully powered up. All the previously mentioned Construction Speed, Dockyard/Factory Output modifiers will also be scaled accordingly to the % of the energy you have.

This is the current debug display that allows us to see energy demand & consumption, and how much it impacts the industry. In this case we have 26.7% energy needs satisfied, and it means that each of our CICs provide 4.2 IC daily, MIC provides 3.7 IC daily and NIC provides 2.1 IC daily. Of course as usual, reminder that all values are subject to change.

[h3]Wrapping up[/h3]
And that is all from this dev corner. While this post is one the shorter side, impact from adding this ‘system’ could of course be quite big - however thanks to covering only this one matter, feedback, opinions, suggestions from you dear readers, should be laser-focused and allow us to get a much clearer picture of what you are thinking. Anyways, that is all from me for this week, and next week Thomas will be back with more things to say about the Factions.

Thanks for reading, and until next time, farewell!

/Zwirbaum


If you haven't already seen it, the Steam Summer Sale has now begun!
Either Click the above image or here to check out the store page

Generals!

The Steam Summer Sale has arrived, and the Quartermasters have facilitated more deals for our frontline troops, make sure to check them out before time is up! Pick out something for your collection, grab something for a friend, or maybe find that one thing you've been missing for your next games!


[h3]BASE GAME[/h3]
Hearts of Iron IV - 70% off Hearts of Iron IV: Starter Edition - 70% off

[h3]Expansions[/h3]
Hearts of Iron IV: Arms Against Tyranny 20% off Hearts of Iron IV: By Blood Alone 30% off Hearts of Iron IV: No Step Back 30% off Hearts of Iron IV: La Résistance 50% off Hearts of Iron IV: Man the Guns 70% off

[h3]Country Packs[/h3]
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[h3]Music & Unit Packs[/h3]
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Have you kept up with our latest Dev Corners? If not, you should check out this post to find all of the recently discussed things shown by developers

[p]Last week's Dev Corner can be found here, but let's begin the next one!


[/p][h3]Briefing: Hydrodynamics[/h3][h3]Written by: Zwirbaum[/h3][p]
Hello everyone!

Another week is upon us which means it is the time for another dev corner. Last week Thomas talked about what we are cooking with the Factions, while I will be talking about naval and naval-related changes. Even the most beautiful placeholder art will be gone eventually like tears in the rain. So strap in, and prepare for the deluge of the information that will be coming your way. Also, keep in mind that everything discussed here is in a relatively early stage, and as such is subject to change.

It is no secret that one of the most common sentiments across the Hearts of Iron IV player base is that the Navy seems to be rather hard to understand. Some elements are almost instantaneous in the effect (Supremacy), others take a long time (building the Navy) and some elements remain relatively hidden until the actual shooting starts (Supremacy Value of the Ships, Screening in Taskforces etc.). On top of that we are also having a fairly complex system of Naval Missions - where they work best when using them together, synergistically. However missions could be explained a bit better, and sometimes what is best to achieve your goal could be somewhat counter intuitive. (Giant Strike Force of Doom, sitting idle in the port somewhat projecting supremacy across the entire oceans without ever sailing out as one example). So how are we planning to address it?

[/p][h3]Core Concept[/h3][p]Similarly to how last week we talked about high-level concepts for the Factions, I will try to do the same for the Naval Systems, but before that I will also list some of our goals that were the basis for what we are working on:
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• [p] Updating and Reshaping Naval Gameplay, making it more strategic, giving you the opportunity for the counter-play if needed; a bit more predictable, and less ‘flip-floppy’
  [/p]
• [p] Updating Naval Missions so that they become more intuitive, with a much clearer purpose and use case
  [/p]
• [p] Encourage a more active use of fleets
  [/p]
• [p] Update and Communicate better to the Player some of the intricacies of the Naval Systems
  [/p]
• [p] Increasing the Importance of the Islands Control (in the Pacific) and Naval Logistics
  [/p]
• [p] Updating Carriers and address the interactions between land-based aircraft and naval taskforces
  [/p]

[p]
[/p][h2]Update to Naval Gameplay[/h2][h3]Naval Dominance[/h3][p]First of all, and the most important of the changes is that we are introducing the concept of Naval Dominance. Naval Dominance is a sort of umbrella term for a couple of things. Similar to how ships had Supremacy Value, now they have Naval Dominance Value, which will be displayed on the Ship Card.

Mutsu has 509 Naval Dominance Value. We are also changing the old calculation, that was based mostly on Production Cost and Manpower, to have more things affecting the calculation, like Speed and Range, so for those who want to build Fast Battleships, increased dominance value may be the reward…

Next, we will want to talk about Naval Dominance - which is our way of indicating naval control of sea zones. Each Sea Zone, depending on the terrain type, has a certain threshold of dominance points you need to have before you can claim you ‘control’ it. And if you are at war, then similarly to the older system, you are also taking into account enemies' Dominance Value and the ratios between you and them. Also the ratio needed for ‘control’ now has been adjusted to require 66% instead of 50%+1.

Having control, or as we call it now, establishing Naval Dominance in a Sea Zone, provides you with certain advantages and bonuses. For instance, as you can see in the screenshot below - potentially reducing the amount of convoys needed for Trade and Supplies by up to 25% if you have secured the entire shipping route.
There are other benefits that I will not fully reveal yet, but amongst other things, there will be something to help you secure islands and potential naval invasion targets.

In this example we can see that in order to claim ‘control’ over the Deep Oceans sea zone, you would need to accumulate at least 1000 points worth of Dominance, assuming nobody would contest you.

[/p][h3]Dominance Gain[/h3][p]This tooltip shows the information about the current amount of dominance accumulated in this sea zone, how long it will take to establish its full value, things that impact it, like airbases located on the islands in the sea zone etc.

Dominance as opposed to the previous supremacy system now takes some time to establish, but it also doesn’t simply instantly disappear when ships engage in combat, or go to repair after a battle.

[/p][h3]Naval Mission Updates[/h3][p]We will also be making the following changes to Naval Missions. We will divide current missions into 2 groups; Core Missions and Auxiliary Missions.

Core Missions - (PATROL, CONVOY RAIDING, CONVOY ESCORT, STRIKE FORCE)

Those missions are your primary way to interact with naval dominance. Each mission type will interact a bit differently. As it is right now, Patrol will be serving for Building Up Dominance, Convoy Raiding reducing Enemy Dominance, Convoy Escorts will provide a ‘protected’ value, which means enemy raiding won’t be able to reduce your dominance below that value, and Strike Force serving as a ‘Synergy Tool’ - and amplifying other missions. Hopefully this will provide a clear and relatively intuitive system on how to use the Naval Missions.

Auxiliary Missions - (NAVAL EXERCISE, MINELAYING, MINESWEEPING, NAVAL INVASION SUPPORT)

Those missions do not interact directly with naval dominance, however, they do benefit from it, like for example, being able to minelay or minesweep faster and more efficiently when operating within a region where you have established control and have naval dominance.

[/p][h3]Naval Home Bases, Range & Supply[/h3][p]This Dutch Fleet has set the port in Batavia to be their Home Base.

We are reintroducing the Home Base system for the Fleets. Each Fleet needs to have a Home Base. Any Naval Base that you have access to (Your own, Subject or Faction Members, or if you have secured Docking Rights) can be selected as a Home Base. So the question is; what does the Home Base do?

[/p][h3]Naval Range[/h3][p]One of the changes that we are doing is that the ship's range is now projected from the Home Base instead of all Naval Bases.

As you can see depending on where Home Base is located, the range, and access to do the Naval Missions is quite different. A fleet with Königsberg set as Home Base does not have the range to do the missions in Norwegian Sea or Western Approaches Sea Zone.

[/p][h3]Naval Supply[/h3][p]Previously, naval units would always draw the supplies from the Naval Bases closest to where the taskforces were operating, now - they will be drawing the supply from their selected Home Base.

This fleet has a Home Base set in Honolulu - and is operating in the Micronesian Gap. Despite the port in Johnston Atoll being closer it draws the supply from Hawaii Naval Base Supply.

[/p][h3]State Building Limit - Islands[/h3][p]In Götterdämmerung we introduced terrain-based limits for province-based buildings like Forts and Coastal Forts, so that you couldn’t build the Maginot Line everywhere. In a similar spirit, we will be introducing state-based building limits for the buildings. In this case we are now focusing on putting limits on the various Island categories, so that not every single tiniest of islands can have an airbase capable of storing and launching for missions 2000 planes every day. Right now those caps are based on the Island state categories (Tiny Island, Small Island, Large Island), and upon one concept we will talk about in the future.

Marcus Island can now have at most a level two airbase and level three naval base. Those limits as all the numbers, stats and values are of course subject to change. Also there is totally nothing hidden under that Hearts of Iron IV logo.

Short Comment
Initially when I started writing this section, I was going to write how I envision things mentioned so far will change the naval gameplay, and how X will impact Y, however I think I am more interested in hearing what you, my dear readers, are thinking and your opinion on what you have read today.

[/p][h3]Naval Invasions[/h3][p]We are doing some touch-ups to the naval invasions as well. In the current live version of the game, there is a global naval invasion capacity set by your technologies, doctrines and other modifiers, and then depending on how many divisions you assigned to the invasion, it would take a certain amount of time to plan that naval invasion. This system unfortunately had one issue, that in order to be ‘optimal’, it encouraged to spam 1-division naval invasions, as that technically allowed you to have a massive naval invasion planned just within a few days, at the small cost of carpal tunnel syndrome.

In the new system, there will be, depending on your technologies, doctrines etc. a certain amount of naval invasions you can plan at the same time, each being able to have a certain amount of divisions, and no matter what, always taking a specific amount of time to plan.

Also, for a country that hasn’t researched even the basic Transport technology, there will still be a possibility to launch a very limited naval invasion under the new system.

[/p][h3]Appeal to my Lizard Brain[/h3][p]And last but not least, I’m going to tell you about one more thing - and that is that we are adding visual representation of control over the seas, visible on default map mode, which during a conflict should represent a gradual shift of control over the zones, giving the feeling of ‘naval frontlines’. Also this can serve as a kind of warning, that when your coastline sea zones start displaying your potential enemy colours.

This is the current prototype of showing on the default map mode who has naval dominance. In this case Japan has the most dominance, and nobody is effectively contesting it, thus Japanese colors are displayed on the map.

[/p][h3]Wrapping Up[/h3][p]So, to wrap things up, this is just a number of things we are doing for the Naval. I have not touched upon anything Carrier related, new equipment or new tools yet, or any UX/UI updates. I will return in due time to provide you with more information on all the things that are not-dry, in the meantime - here is a teaser of a thing that we may talk about in the future, with this beautiful placeholder art done by myself.

Who will guess what this is?

This is my first dev corner, so I can only hope my writing is not too stiff. In time I hope it will get better.

Anyways, thanks for reading and until next time, farewell!

/Zwirbaum




Also, we have a survey for you to fill out when/if you have time regarding Naval Gameplay. Just keep in mind that this Steam thread is for your feedback about the Developer Corner. If you have feedback about this specific survey we welcome your thoughts in a separate forum post, or in the HOI Discord!

EDIT 25/06/25 - Thank you to all participants for the Player Survey, this survey is now closed!

Click the Image above or this text here to fill out the survey

[/p]

[p]Generals!

We return with new intel from Command, a new War Effort is now live with balance and gameplay tweaks, UI and performance changes and a bunch of bugfixes, make sure to read them all below;

[/p][h2]Balance[/h2][h3]Afghanistan[/h3][p]- The focus Socialist Coup can now be bypassed if they are already communist, and the coup can be performed peacefully if there is more than 60% communist support in the country
- Countries will be more likely to accept your Confederation with Pakistan if they are in the same faction as you
- The focus Reform the Quami now grants an additional 10% recruitable population factor
[/p][h3]General[/h3][p]- Removed hostile armor speed factor from German Blitzkrieg operational planning modifier; this modifier only half-worked by virtue of a bug that has now been fixed
[/p][h2]Gameplay[/h2][h3]Afghanistan[/h3][p]- Mohammed Daoud Khan now becomes a general if going down the Nufus branch
- Added a focus to the Quami branch that allows for the production of cheaper, but less efficient rifles
- The army branch now contains two focuses relating to utilizing Camels in the military, with one of the focuses requiring Battle for the Bosphorus
- Added a focus to the industrial branch to expand the Spinzar Cotton Factory, granting two more civilian factories
- Added a focus accessible to the non-aligned/democratic branches about constructing a national identity, gaining strong bonuses after some investment
- Added new focuses to the Nufus military branch, to gain a larger army, and potentially seek mutual guarantees with Turkey[/p][p]- Added a strong capstone focus to the Nufus branch that references the historical title of the Royal Afghan Army; Prussians of the Orient
- Added 4 new political advisors
- Added Traditionalist Paths to the Against Kabul Branch
- Added three new low-probability expansionist AI Strategy Plans
[/p][h3]France[/h3][p]- Improved the description of the focus "Fatherland"
[/p][h3]India[/h3][p]- Added a news event for the formation of the East India Company
- Added a news event for the Royal Indian navy Mutiny when India flips communist
- Added a news event for the Death Knell of the Raj
[/p][h3]General[/h3][p]- Overlords capitulating now always gives half progress to next autonomy level, disregarding of which autonomy level it currently is

[/p][h2]UI[/h2][p]- Fixed an issue where army composition summary in frontline tooltip would show incorrect information
- Added the option to disable map corner scrolling while keyboard navigation remains enabled
- Added hotkey for accepting diplomatic requests quickly by Shift + Left Clicking top bar alerts

[/p][h2]Performance[/h2][p]- Improved multiplayer save file transfer speed significantly, which should help resyncing to be much faster than before

[/p][h2]Modding[/h2][p]- Added "after" (as opposed to "immediate") effect scope for events

[/p][h2]Bugfix[/h2][h3]Afghanistan[/h3][p]- You will no longer lose your own core states when gaining Tajikistan or Turkmenistan as allies when declaring war on the Soviets after having completed the focus "Alliance with Turkic Peoples"
[/p][h3]India[/h3][p]- Pakistan and Bangladesh will no longer be counted as Princely States that break away from the Raj when declaring war as the Mughal Empire after having completed the focus "Revolt of the Princes"
- Fixed an instance where UK could swap India communist by completing decolonization while a dynamic india tag existed
[/p][h3]Iraq[/h3][p]- Muhammad Amin Zaki now correctly becomes available if you complete the Encourage Federalism focus
[/p][h3]Turkey[/h3][p]- The turkish focus "Taking over Defense of the Gulf" will no longer allow Britain to transfer states it does not own and control to Turkey
[/p][h3]United States of America[/h3][p]- Fixed an issue where America could not flip fascist because a decision was hidden
[/p][h3]General[/h3][p]- Fixed an issue where installing modules did not play sound effects when MTG was disabled
- Fixed issue where random character names would not apply to modifier tooltip
- Fixed tooltip showing wrong country in naval combat
- Fixed laws not applying to revolter in civil war
- Fixed an issue where alternate icon settings would inadvertently revert to default settings
- Fixed an issue where Diplomatic Pressure would be set to zero after reloading a game
- Fixed an issue where having the Diplomacy window open would highlight the International Market icon in the top bar
- Naval Aircraft MIO archetype now actually adds Naval Attack / Naval Targeting / Sub Detection and Surface Detection to their planes.
- Changed display of matching MIOs in production line creation from "available / total" to just "total" due to obsolete differentiation
- Fixed an issue where generals could be displayed as belonging to the wrong nationality in the Battle window
- Fixed an issue where the custom rule for Maximum Fort Level would not be applied correctly
- Fixed an issue where strait highlighting could get stuck when switching from the navy map mode
- Targeted decision cancel_effect will now execute if the target is invalidated but also happens to be a valid country with no provinces, this should resolve various issues with targeted decisions such as European Union invitations locking themselves into an invalid state
- The Suez Canal will no longer display an unlocalized string in its tooltip after being blown up
- Prevented dynamic state modifiers to speed from a) setting their value instead of adding, and b) applying twice. This resolves issues with certain mechanics such as Ethiopia's Decentralization system setting unit speed to 1km
- Sweden can no longer trade ball bearings with a country it has embargoed
- When the East India Company is formed while India is a subject of a nation other than the UK, Britain will no longer become the overlord of the Raj
- Fixed an issue where switching Trade Law to Closed Economy would not always cancel all active exports
- Fixed issue with ship weather penalty reduction also reducing positive modifiers (this will mostly affect destroyers - by quite a lot)
- Foreign countries (usually Japan) will no longer lose control of British Malayan territories if they transfer allegiance to Australia through the Australian focus tree
- You can now correctly load heavy cruisers from persistent equipment designs
- You can once again upgrade MIO on basic equipment if you chose not to upgrade it automatically
- Added 30 days of sanctuary from changes in autonomy level after recent change
- Made sure MIO selection window closes properly when switching between equipment designer types
- Observers can now always see the combat log of the observed country
- Fixed an issue where swapping production lines to licensed equipment would keep any MIO assigned
- Fixed an issue that would cause auto-design to apply MIO to licensed equipment
- Fixed an exploit that allowed licensed equipment being turned into owned tech
- Fixed a CTD in multiplayer when a client was building railways during a hotjoin




[/p]