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Hearts of Iron IV Anniversary Week & Developer Corners!

Generals!

Not only is our nine year anniversary happening today, but we've got a lot of content for you all to read through so make sure to continue reading. We've got Developer Corners starting up again, HOI4 Anniversary Giveaways every day and the Multiplayer Mayhem happening in the 2025 Community Cup!


But first, a word from our Commander in Chief @Arheo .


Greetings all,

As the oft-quoted Eisenhower stated, ”In preparing for battle, I have always found that plans are useless, but planning is indispensable”. In the spirit of this, we thought it would be time to take a look at the long-term roadmap for Hearts of Iron. It has been around three years since our last formal Hearts of Iron Roadmap, and while plans have changed and evolved, this statement of intent has been largely what has guided our development process up until the release of Götterdämmerung.

Our mainline intended innovations, when this was written just after No Step Back, included the following:
  • Improvements to Frontline Stability (Progress in NSB, more to come)
  • Strategic and Tactical AI improvements
  • Battle Planner Improvements
Götterdämmerung included a lot of improvements to the AI including Force Concentration: a feature designed to simulate tactical pushes and armor concentration. This has been an interesting one: when released, we saw a lot of players taken by surprise by the AI using this approach, and a lot more discussion over players being defeated or losing to the new AI behaviour. However, most of the community seems to have adapted fairly quickly to this change. To me this is a positive thing: while having a broad playerbase with varying levels of skill means we need to be gradual about how and if we increase overall difficulty when playing against AI, the existence of community “meta” and learning materials gives most players tools to catch up. In short, there’s no reason not to continue iterating on AI features that may increase average difficulty or required skill levels.

On a related note, we’ve fixed a bunch of issues with frontline stability, but battle planning remains a tool that has a stark divide between how new and veteran players utilize it. We’ve done some quite deep user research into this particular area, but this resulted in few actionable results beyond handling edge cases better and improving frontline integrity.


Long Term Goals and Strategies to guide AI (Progress in NSB)

Most of this is “under the hood”, but we’ve made a lot of progress adding tooling to interpret and direct how the AI performs long-term planning. This area of the game is notoriously opaque and it’s taken a fair while to get to the point where we have enough analytical insight into the mechanical decision-making process of the AI, but, we’re more or less there now. This has meant improved tooling such as AI strategies, imgui debug tools that modders also have access to, and better integration with existing mechanics that previously existed “on top” of the game without interacting much with the AI. This is of course a goal that has no defined end-point, but compared to where we were three years ago, much has improved.


Improving Peace Conferences

By Blood Alone saw a contribution-based peace conference system added, with numerous narrative demand options. On reflection the design approach here was not super stable, and while the feature hit most of the key notes (contesting demands, earning defined contribution, rewarding better play), it fell into a similar trap to the old system when it came to AI antagonism. It took longer than it should have done for that behaviour to stabilize with tweaks and changes, but we’re in a better (if not perfect) situation now.


Update Core National Focus Trees with Alt-History paths alongside more Options

We’ve had a couple of methods of doing this. First are the maintenance updates included in some War Effort patches. These tend to be quite minor, but we’ve added a fair few things to various focus trees over time.

Secondly, revisiting focus trees such as Germany and Hungary represents a greater investment into this. Overall, I’m happy with the dual-pronged approach to this; reworking focus trees comprehensively is a full expansion-cycle affair, and doing it outside of a paid release is not something we will ever be able to do. I feel the majority of the community understand this, and our roll-in approach to DoD, TfV and WtT has been for the most part welcomed.


Great Power Diplomacy

I’ve spoken at length on this in a few other places. Fundamentally, design ideas for this one always ended up conflicting with focus trees. HoI4 is a war simulation with a superimposed latch-driven state-machine that drives the global narrative. It is unlikely we’ll change that approach. However, the process of working through design ideas for this has given us some avenues for further exploration.


Multiplayer & Social layer Improvements & Support

The Career Profile and associated features hit the social layer note pretty well. Traditionally, these features are designed to increase player engagement: something which HoI doesn’t really have an issue with. However, the feature has proven to be unexpectedly popular amongst specific groups within the community, both for completionists and as a learning aid. While I don’t think we’ll be making any fundamental additions to this, it won’t be going away and we’ll keep adding content such as new medals and ribbons.


Economic Decision Making

We haven’t made any great strides here. We still have medium to long term plans to expand the industrial economy elements of HoI, while taking care to avoid simulating too many pure economic elements.

Special Projects

Götterdämmerung represents the culmination of this project. I’m pretty happy with how this turned out, though now that we’ve had some time to monitor the wider effects of special projects, it is about time to revisit balance and take a pass on the huge array of tech that was added in the Götterdämmerung update.


More Difference between sub-ideologies & Government forms, Advisors and Internal Politics Improvements

We didn’t really get here! This is quite a difficult topic to broach in a strategy game, and other things ended up taking precedence. We’ve had some minor changes to advisors, but nothing to write home about in the grand scheme of things.


More National Focus Trees

Fairly Self-explanatory.


Make Defensive Warfare more fun

This is still a goal of mine, but we haven’t managed to tackle it yet. I think some of the fundamentals of HoI4 (ie, stuff we simply can’t/won’t change) stand in the way of doing this justice, though it also plays hand-in-hand with changes to doctrine and division design which are definitely in the works.


Adding Mechanics to limit the size of your Standing Army, Particularly post-war etc

Definitely still planned, though not a major priority on its own - will have some words on this later. I don’t feel like this is something that has been glaringly missing for a game with a narrative of “crescendo to war”, though as we start to experiment around the fringes of that pillar (smaller regionally-focused conflicts and expansions), it will become more necessary.


Have Doctrines more strongly affect Division Designing

We’ve had some success here with the changes to support companies and equipment streamlining. I wouldn’t go so far as to say this is “done”, though. We have short-medium term plans regarding doctrines though, and having them affect division design more strongly is one of the key pillars for this effort.


Immersion and Roleplay Elements, Optional tools for making your mark in a game

We’ve added a lot of things that touch on this: division medals, plan naming, deeper recruitment design, MIOs and industrial specialization being chief among them, feature-wise. I think these features do what they set out to do: letting you leave your own mark on the battlefield and the campaign narrative. As you may have noticed from recent war effort patches, we’ve also identified that we need to be better with streamlining how players interact with these types of features.


War Effort Updates

I talked at length in the 2022 roadmap about the introduction of maintenance updates - something we ended up doing, and calling “War Effort” patches. On their own merit, these have been extremely useful for us, and have allowed us to iterate and introduce quite a lot of system updates and quality of life changes such as:
  • Persistent equipment designs
  • System Rebalances to designer modules and units
  • MIO streamlining
  • Some quite significant performance improvements
  • Over 1000 bugfixes
  • Mod support
  • Focus tree updates
  • Balance standardization of some systems (quite important for game health!)
One of the things we were uncertain of before we started War Effort patches was whether this would reduce the maintenance included in major updates, resulting in effectively just moving things around. With the exception of our approach to country packs (ie; not including maintenance updates at country pack release), it has not directly affected the size and impact of major releases.

The old Roadmap championed these as a method of updating older focus tree content. It’s fair to mention that this ended up not being a major focus of war effort updates. It became quickly apparent that developing focus trees is the majority of the work our Content Designers do; that’s not realistically something we can do in iterative updates.

So while there is success here, there’s also room for improvement. We will keep producing War Effort updates, but I want to try and find some form of structure to them, and a way of steering them in a way that more quickly addresses high impact community issues. Particularly, I would like to find a way to increase the visibility of our approach to handling community issues, though I will caution that this will require some time to achieve.


Next Steps

Aaand that’s our retrospective.

That ended up quite a lot longer than I’d expected, but that’s ok - the future plans are at least a little more concise! I want to give you an updated roadmap for our next few years, though with the usual caveats. As you can see above, these plans are not super specific, they aren’t promises, and they don’t always work out. Nonetheless, the act of planning is extremely important, and communicating those plans perhaps even more so.

So what does the future look like for HoI4?

It will come as little surprise that South/East Asia is next, with content primarily focused on Japan and China, and mechanics to support this narrative, as well as reinvigorating the Pacific war. I don’t want to go into too many specifics here (tune in next time for more!), but the war in and around Asia as well as the Pacific has been left behind by our recent developments directed at the European elements of the conflict. To give some broad strokes here, we’re looking at developing the narratives that faction membership will give you, improving and streamlining elements of naval control, with a particular focus on the types of naval warfare that carried the Pacific conflict, and adding much greater strategic narrative (and a less opaque simulation) to the flow of naval conflict. This is not an exclusive list, and it’ll probably leave you guessing - but you won’t have to wait long.

In the longer term, we have some other areas that we’re keen to take a pass on:


Military Doctrines and Division Design

These systems are quite old and don’t offer much ability to shape your gameplay. I would like to link these better, in order to have doctrines shape both how you compose and how you use your military.

Manufacturing and Industrial/Economic Gameplay

Watch this space.


Breaking the Snowball!

HoI’s “crescendo to war” that I mentioned earlier is extremely important to the main narrative of the war. However, as time goes on we have released more content focusing on the smaller players in this conflict. There are elements of the game that don’t mesh particularly well here, and I want to take a look at the way wars and war escalation are structured to make this more engaging and less disruptive when minor conflicts erupt.


Improving the Diplomatic Landscape

“But you said you couldn’t do this!”, I hear you cry. And mostly you would be right. However, with the introduction of late game technologies in Götterdämmerung, there is even more reason to continue playing after the end of the war. I would like to keep developing how the world “falls out” after the conflict, producing more realistic geopolitical results as well as the potential for new and more systems-driven “what if” conflicts after the end of the war. Of course, any such changes would be multiplied in effect if they could also touch upon the pre-war landscape too…


Alt-History

Well, that’s a broad category. This is one we’ve been looking at in quite a lot of detail. We see an increasingly stark divide within different groups of the community on how we (or even if we should) approach alt-history. For those that enjoy it, don’t worry, we’re not going to stop making alt-history content, however, I have asked the team to look, in the long-term, into ways of producing more structured, plausible alt-history content with clearer historically-adjacent narrative hooks. In addition, we have started to evaluate if it’s possible to create more deterministic global alt-history situations and produce some “semi-alt-history” ways of playing HoI - something that I think would capture the fun parts of the non-historical content we provide while also retaining the benefits of the determinism that the historical scenario imparts.

I have one, final note on the practical elements of what we release. We intend to continue releasing what we’ve previously termed “Country packs” and “Unit packs”, but we need to both be clearer about what is or isn’t included, and adjust the scope. We’re devoting some more resources to our Country pack development moving forwards, and we’ll be including mechanics and systemic changes in those the same way as expansions - albeit still focusing on “minor players” in the war.

Alright, I started writing this three hours ago and apparently I’m still going, so here I will force myself to stop. I’m here to answer questions.

/Arheo


Hearts of Iron IV Dev Corners 2025 Roadmap - Updated: June 16

Of course, these dates may be subject to change so keep that in mind!


Hearts of Iron IV's 9th Anniversary!

As apart of HOI IV's Ninth anniversary, we've decided to do another giveaway with a different prize each day including some fan favourites and some keys for the new Song pack for those of you who missed out on some of those banger tunes. To participate and enter for a chance to win some of these codes, make sure to reply here on each day you want to take part in the giveaway.

Because of time zones, we've decided that each giveaway "day" will start at 14:00 CEST, so for example, if you want to take part in the Bonus Songs Pack giveaway on Tuesday, then you need to reply between 14:00 CEST on Tuesday and 13:59 CEST on Wednesday. If you reply on Wednesday 14:00 CEST, then you're taking part in the Wednesday giveaway, etc.

You can reply as many times as you want, on as many days as you want, but if we're looking through replies and have to choose between two replies, we will probably choose the reply that has some substance (vs "Just replying to take part") so be creative, engage, comment on the announcement or on others' replies.
(Giveaway T&C attached below)

Today: HOI IV Starter Edition So you can play with more friends x30
Tomorrow: Bonus Songs Pack To listen to, even when you're paused x30
Wednesday: No Step Back To bring Communism to the world x30
Thursday: By Blood Alone Take your fight to the skies x30
Friday: Arms Against Tyranny To bring the fight to the Nordics x30

Hearts of Iron IV Anniversary Sale!

To add even more fun to our anniversary celebration, the Hearts of Iron Sale (up to 70% off) is now live over on paradox.com!

Community Cup 2025

We are back for yet another round of the Community Cup, hosted by Dankus. This year, the Teams are participating for a chance to win 5000 Euros! With Casters such as Dankus themselves, Mo and one of our own Community Ambassadors Fraser, the finals will be played June 7th at 17:00 CEST.

Make sure to catch all of the action over on Dankus's Channel, or the HOI Youtube Channel!
 

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Yesterday I shared some of my ideas on Japan. Today I thought I would do the same for some other aspects of the expansion.

Regarding faction dynamics: one thing I often found a bit silly was that there seemed to be no negative effects on opinion for refusing AI's calls to join war. You could be completely selfish as much as you want and never help anyone, but when you request help, they are absolutely going to help. Now, there would need to be some balancing around that idea. Maybe let the AI not call allies if their enemies are noticeably weaker (while still leaving the option to join voluntarily open)?

Also, and this doesn't only include faction members, but it's still in the realm of diplomacy, the AI is sometimes a bit too quick to cancel lend-leases. Seems to happen as soon as the stockpile is no longer in the negative. Perhaps there should be some reasonable threshold for that? Like, they could still want you to be in the negative to start the deal, but once it's been signed, let it run for a little while?

That's all for now, but hopefully more stuff will come to mind tomorrow.
 
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Giveaway entry.

Remember old Italian focus tree? A focus tree where you could bypass 1/3 of the focuses, and where War in Ethiopia would last until 1939, and when you joined ww2 you had gigachad generals. I polished most of HoI4 on that tree. But I love the new one, especially the naval branch, people usually underestimate Italian warship designs and navy, Italy actually had the 4th largest in the world, and had great ship designs, They were flawed with the lack of radar, some ships did get radar systems, some were from Germany, and some were prototypes that were pulled from the storage houses, but the effort would be stopped by armastice with allies.
I had many fun campaigns as Italy, most of them tied to the navy, and the reclamation of Mare Nostrum, chasing the British warships in the Mediterranean, and them chasing me back, actually feeling that deploying another pair of heavy cruisers will matter, and struggle to keep up destroyer production. Breaking through Suez into Indian Ocean to try and link up with Japan and help fight the USN.
Or failing miserably by having one bad naval battle, and then trying to nurse back up, to replace losses, to try and trick the British, to gain an edge in the long war under the Mediterranean and African sun. Trying to catch a smaller British fleet in an ambush, and using asymmetrical warfare to keep reinforcements away. Both sides giving each other small cuts in the shape of convoy raids, trying to bleed one another. The North African front moved back and forth many times. Trying to push the enemy out of their supply hubs, outrunning the logistics, and overextending, just to be halted on the gates of a crucial port and supply hub, then being pushed back to yours, and repeat.
After a large but still indecisive naval battle, scrambling all available bombers you have to try and score a victory, to at least keep the enemy in drydock for few more days. Because you know that after the Giant wakes, the line will move away from the African and Mediterranean and be drawn closer to the old country.
I guess I didn't really say why I want to get the DLC, but I just love playing Italy.
Ah yeah, my first campaign after Patch Avalanche were added. Having the game runs all the way until 1951 and still did not run out of focuses feels awesome, same as Soviet Union's 1952.

I hope Japan would have the similar-sized focus tree, or at least one that still has available focus in 1947 since there would be a lot of work already given for all six of Southeast Asian polities.
 
Reading the DD again, I'm quite intrigued by the "semi-alt-history" and faction dynamics. As an achievement hunter, the bane of my playthroughs is a random minor unexpectedly declaring war on my target, drawing it into the Allies and forcing me into a world conquest. Historical is more predictable but countries like Norway or Denmark are far safer with a monarchist Germany off their back. A less chaotic alt-history would bring variety without the risk of, say, Portugal somehow causing a war between Allies and Comintern.
 
So, there's 2 big thing i want to ask...
1. the new era... thing...
if it's what i think it is, which is post-war, end of colonialism in africa and asia, to early cold war, that's kinda beg the question of will it brings new focus trees and narratives because most nation that has historical events in the post war era doesn't exist if we based around the 1939 start, and even if they can be formed, they kinda have a common focus tree and narratives which does disservice to History itself.
and if the teams willing to do add them, that will add more strains to the engine and bugs to be stamped.
so, i may ask, how would you tackle it with the current engine?
2. SEA focus trees
first of all, thank you for reworking China and Japan focus tree (kinda realistic AND ironic that the oldest unique focus tree in-game is from asian nations :v) and trying to create unique focus tree for the SEA gang (which is my home region).
but my question is, how would you do justice on the historic path of those nations? with the malaya and singapore granted freedom (or forced to be free in case of singapore) by the british, Vietnam fighting the french which directly led to the vietnam war, and indonesia against the dutch for their independence.
and by reworking China and Japan's focus tree, you kinda have to make a new focus tree for Korea too.
 
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@Arheo :
Early in your OP you said "battle planning remains a tool that has a stark divide between how new and veteran players utilize it." I'd *love* to see what this divide is!
 
I wonder what the island hopping campaign will be like. I found naval landings to be quite bothersome compared to the pace of the land warfare, I hope the new island hoppings will be more fun :D
 
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By blood alone is a dlc that i haven't bought because of the criticism. Even thought Italy is one of my favorite nations since my first playtrough.

I would love to try another campaign as them with 'by blood alone' and check out how the different plane models work
 
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It would be interesting to see a League of Nations system-it could involve a way to de-escalate conflicts such as being able to demand concessions and new ways to hinder the aggressiveness of countries in the early game. It would also give an excuse to add League of Nations Mandates which would effectively be a more direct version of supervised states, just without being forced to let them go free.
 
Please don't forget France for the next DLC, for a major country it has no 3D representation for its motorized and mechanized infantry, no representation for its special forces as well as for most of its infantry models which are far from being all the same, the models for aircraft are also very few. You said you wanted to improve the game in defense France would be the ideal country for a DLC on this theme especially with the Maginot Line, moreover you would also like to improve diplomacy and I suggested an empire management especially for France but also the British. In conclusion I want to tell you that your work is superb and I really appreciate the game but please do something for France
 
Amazing. Can't wait for the East and South-East Asia rework!! (and maybe getting By Blood Alone to almost complete my DLC collection :D )

I have no possible idea how you would change the pacific warfare at this point. But making all these small islands way more important and not skippable on your way to invade a country on the other side of the ocean would be more than logical. Maybe the supply system will be modified again? There could be buffs and debuffs for your troops and maybe even your fleet. Can't wait to see your ideas finally come to life; I really like that you're putting more depth into the game mechanics.
 
Manufacturing and Industrial/Economic Gameplay

Watch this space.
Could be a bit optimistic for this to involve sorts of oversight with stuff like trade laws where resources to market always locks you out of them (even when there's no one to import so no civilian factories to benefit from their absence)

although an oversight probably more fixable than my continual problems with matching a certain nation's economy to their historical arms export sales - can't exactly hope it will exactly ever be balanced given the existing ability of said nation to solo Germany + the obvious problem with Germany being buffed even more with the historical annexation...

Think I do need to try the previous Hearts of Iron games to figure out what exactly it is people talk about when praising (one of) them for making mobilisation as a mechanic feel so impactful, hopefully that is what can be achieved with this manufacturing and industrial/economic gameplay idea at the very least.
 
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Since they talk about doing some post-war things, was there talk about extending the timeline? Like getting into the early 50s for the Korean war and having the Allies fight the Communists?
 
For the post-war dynamics, it would be highly interesting to see the United Nations represented. A way it could be done is if after 1944/45 there is a point in time with no majors at war with each other they can choose to enter into an event chain to decide the specifics on how that version of the UN would work and who would be on the security council. While this likely wouldn't have a very large impact on gameplay it would act as a nice sort of endpoint to the play through, setting up the Cold War and post-war world order. It could also provide an avenue to deal with remaining conflicts by the time it forms.
 
That tease for Manufacturing and Inustrial/Economic Gameplay has me intrigued. Sure, HoI4 is about the warfighting of the WWII time-frame, but one of my favorite parts is putting together the national economy to support the war effort. My early game is split between the tech window and the industry window, counting down the days until I can do the next thing. So, to say I would be excited for any expansion or deepening of the Industrial and Manufacturing systems would be something of an understatement. (My favorite techs are in the Industrial branch, as they allow me to build both more and faster.)

Just as a side note, I've noticed that the Land tab allows you to see which armies are currently in training mode, and the Naval tab shows you which task forces are training, but the Air tab has no indicator for which air groups are in training. You have to click in to each air group to see whether they are training or not. Seems like an oversight to me, but I'm just a rando on the internet.
 
My suggestions For the updated Japan Paths:
The democratic path could centre around trying to peacefully free Asia from colonialism, akin to the old path. In this case however it would involve creating a
Co-Prosperity Sphere that actually improves the prosperity and development of the members other than just Japan. In doing so, this would create shield of democracy and free trade over East Asia. You could then get the choice between trying to help unite China or keeping it separated while making it more subservient to you. It could then choose to invade Siberia to halt the spread of communism in Asia with the choice to peace out with the Soviets for Siberia. Then the player could choose to reproach the allies and help against the Axis or command a great decolonisation war in Asia with multiple peace out options.

The Communist paths would start similarly to the original (civil war, invade Manchuria to finish the war) but then would split between pro-soviet and anti-soviet paths. The pro-Soviet path could be centred around creating a greater communist state in Japan and China, essentially creating East Asia from 1984. The other would be building an alliance (or network of puppets) throughout Japan, China, Southeast Asia, India, etc. This would end in a great anti-colonialist crusade against the allies and against the "fake communists" in the Soviet Union.
 
I'm looking forward for the new mechanics related to the Pacific War and Naval Warfare in general.

Also, just FYI, your T&C doesn't include a list of Eligible Countries.