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HOI4 Dev Diary - Supply and Mulberry Harbors

Greetings all, and welcome to today’s dev diary on the huge supply system update coming with the Barbarossa update. Before we begin, I’ll leave a heads up that this will be the last dev diary before we break for summer, so don’t expect anything new until some time in August at the earliest.

Since we last talked about supply, a few things have changed. We found that the way truck need could take off and spike was hard to deal with and that watching out so you didn't overload individual supply hubs was a bit too intensive. We also felt that the way the mapmode worked made it very difficult to project how well supply was flowing.

The iteration we have now aims at addressing these shortcomings. It's now possible for divisions to supply from multiple hubs. Trucks are now less of a strict necessity, rather something you can assign to hubs to make sure they can project supplies further away. Finally, the mapmode has changed to better show the spread of supply as well as current status for divisions.

Supply flow

From each hub connected back to the capital, potential supply is projected outwards - adding up when overlapping. This is represented by the brighter colors below. For each province in distance that supply needs to travel from a hub, there is a reduction in the amount as some is lost. The amount depends on various factors like terrain, crossing rivers etc. The dark purple areas below are reduced to local supply only, and the highlighted red-orange areas indicate locations where there are units suffering from significant supply issues.

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In the picture above, the Ukraine/Caucasus front is mainly struggling because it is overextending before the captured rails have been converted, so a lot of the rail network there is not operating. When a railway is taken over there is a longer cooldown when it gets converted for use by you (representing a combination of repaired damage, gauge-alteration, and general maintenance), and without connected hubs supply won’t flow.

How much you can output from each hub depends on the level of railways leading back to the supply capital, and the total max there depends on your industrial base (so Luxemburg can not feed as many as soviet union, for example).

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Here, the clock indicates rails that are not yet converted, and the hub icons with red crosses indicate that they do not connect back to your network.

Motorization

To increase the range of a hub (perhaps to help supply the front above better) you can choose to improve the motorization level. The horse icon on the right indicates no motorized supply from the node, but you can opt to toggle it to a higher state of motorization. Be careful, as this will cost you trucks which are taken from the stockpile.

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It is also possible to set the motorization level on an army, in which case it will automatically toggle on motorization for hubs that it uses without requiring further interaction from the player.

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There are also some other options on a hub. The star icon lets you move your supply capital to a new location, provided that you have sufficient surrender progress. This lets you get around issues where your capital ends up cut off or surrounded, but also comes with a period of bad supply as the new location is prepared.

The blue flag next to it lets you control allied access to the node. This can be a great way to flag to an AI that you do not want them on your front, or to stop them from joining a tight landing situation.

The rail icon lets you quickly switch to construction mode and extend rails from there while the green plus will automatically queue up construction for rails to combat any bottlenecks your node may suffer from back towards the capital. The chevron icon lets you prioritize train allocation if you are running low.


Floating Harbors

As part of No Step Back, we’re introducing a new dimension to naval invasions. Floating, or ‘Mulberry’ harbors can now be constructed once the appropriate research has been completed.

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These weighty and expensive pieces of infrastructure (don’t look too close at the numbers above hehe) aren’t intended for every-day landings, but are instead intended to represent the equipment used in large-scale operations such as the Battle of Normandy.

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Naval invasions utilizing a floating harbor will be represented by harbor apparatus placed parallel province targeted by the invasion, and will immediately create a stocked supply hub at their location:

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Used carefully, one or more mulberry harbors can keep a sizable invading force supplied without requiring the immediate capture of an important enemy harbor. Of course, harbors should remain amongst the first targets of any successful invasion, and the supply hubs created by a floating harbor will be temporary; lasting a matter of weeks or months, depending on the strength of enemy air superiority and other factors.

Of course, there is yet more to cover regarding supply, and we'll have another diary on this subject in the future, but I hope you like what you've seen so far and we’ll be seeing you again after summer!

Oh, and one last thing - one of the new loading screens for NSB is this awesome Polish cavalry, so we figured we should share it as a summer wallpaper for you (fear not, there will be a soviet one eventually!)
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The vision behind the painting was to present a more historically accurate depiction of the Charge at Krojanty. This was an engagement in the opening days of WW2, where the elite Polish cavalry surprised a German infantry unit at rest, charged before it could prepare for defense, and dispersed it. They later withdrew when faced with German armored cars.

This battle is famous because it started the, often officially repeated, ahistorical view of Polish cavalry charging German tanks and we wanted to try and make something more accurate (ignore the backdrop. we couldn't resist an epic sunrise on a field, but I hope the feel is there).

We have attached 3 different aspect ration wallpapers for you, and we can't let this opportunity go without a shoutout to @CreamGene our talented 2D artist responsible for this artwork.
 

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Why, then, should (for example) an Australian player not dismantle every port and airfield in New Guinea, starting in 1936? Seems way easier than defending the place.

Well, if he wants to abandon New Guinea, I honestly don't see the problem?

Basically it would be hard to balance. As one poster mentiomed before me, it would render most occupied land useless and conquest would be an even bigger drain on resourcea with barely any bemefits.

Hard to balance what? Of course it should take some time to destroy buildings just as it takes some time to construct them. But I honestly fail to see the "balancing issues" in allowing someone to destroy a port or airfield that they no longer want to keep? Is a piece of occupied land useless for you because it doesn't contain an airfield? Then just build a new one!
 
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Not atm, we felt it probably isnt worth the complexity

Is it possible for modders to change this if this is your approach?

for me motorized logistics using fuel would not only be realistic but will be make choosing trucks over horses a much more of a strategic choice considering how much fuel the axis lacked during ww2 (which was one of the major reasons why they failed in my opinion).
 
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Well, if he wants to abandon New Guinea, I honestly don't see the problem?
Here are a few problems you might not see:
  1. It's quite gamey. Australia gets to keep whatever benefit controlling the state gains them, it just makes the state harder to take from them. Why wouldn't Australia render themselves effectively uninvadable by dismantling every port but one in their homeland, and just holding that one in great strength?
  2. There is inherent supply capacity in a secure anchorage like Wilhelmshaven or Pearl Harbor, even if every plank and rivet of the naval base were dismantled. Being able to damage the port levels makes more sense, but still runs afoul of...
  3. The locals might not appreciate your dismantling their livelihood. If you want to wreck the local economy, you should also pay a stiff price in lost stability, lost compliance, and/or increased resistance for that state. Possibly for every effected state.
 
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Does the blue flag let us control what countries can and cannot use our supply area? For example most of the time I don't mind if Greece takes all its 20 divisions and puts it on my front cause it won't create bad supply issues but it would be great to be able to keep the USA or UK out with their 300 division spam.
 
Hard to balance what? Of course it should take some time to destroy buildings just as it takes some time to construct them. But I honestly fail to see the "balancing issues" in allowing someone to destroy a port or airfield that they no longer want to keep? Is a piece of occupied land useless for you because it doesn't contain an airfield? Then just build a new one!
Require the player to use civilian factories to dismantle infrastructure and it'll probably be balanced just fine :) .

I'm not sure about allowing players to destroy ports, specifically, but at the very least, allow us to damage them 100 percent so that they'll take time for the enemy to rebuild.
 
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Is it possible for modders to change this if this is your approach?

for me motorized logistics using fuel would not only be realistic but will be make choosing trucks over horses a much more of a strategic choice considering how much fuel the axis lacked during ww2 (which was one of the major reasons why they failed in my opinion).
Completely agree with you. Just as it was possible for modder to add fuel consumption to support compagnies while base game made them free by design.

That choice to not make thoses trucks consume fuel might have some reasons we don't know, but please don't make it an hardcoded thing!
 
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Nice work. Are ports now additive and overlapping like supply hubs? In Japan the entire Mongolian front is crippled by having ALL supplies routing through 1 level 5 port. The fix of upgrading this 1 port to level 10 isn't very good either. Massive bottleneck. Multiple ports with overlapping supply would make sense.
 
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Here are a few problems you might not see:
  1. It's quite gamey. Australia gets to keep whatever benefit controlling the state gains them, it just makes the state harder to take from them. Why wouldn't Australia render themselves effectively uninvadable by dismantling every port but one in their homeland, and just holding that one in great strength?
  2. There is inherent supply capacity in a secure anchorage like Wilhelmshaven or Pearl Harbor, even if every plank and rivet of the naval base were dismantled. Being able to damage the port levels makes more sense, but still runs afoul of...
  3. The locals might not appreciate your dismantling their livelihood. If you want to wreck the local economy, you should also pay a stiff price in lost stability, lost compliance, and/or increased resistance for that state. Possibly for every effected state.

1. That's another issue. Of course if they demolish every port in New Guinea then they shouldn't be able to transport anything to or from there either. And just because they don't have a port doesn't mean that they're uninvadable. Read your own point #2 and read this developer diary to understand why.

2. Again, you're bringing up a different issue. If you want to model that, then implement it with a mechanic, not with the inability to destroy your own buildings. What you're describing should not prevent the destruction of a port, but rather make naval invasions more manageble in certain locations even without a port.

3. I think that you're stretching these explanations a bit too far now to be honest. Do you think the locals appreciate having a noisy air field constructed next to their homes? Or a polluting industrial complex? Or a dangerous nuclear reactor? Do you think the locals like being nuked five times in a row? Basically you're defending some far-fetched moral story at the expense of greater strategical control for the player.
 
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@podcat
Two questions;

If I tell my allies to stay away from an area or beachhead, does that means they will absolutely stay away, or just tend to stay away;

and does this new setting apply to airfields as well to keep allies from flooding my airfields and doing nothing?
 
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The blue flag next to it lets you control allied access to the node. This can be a great way to flag to an AI that you do not want them on your front, or to stop them from joining a tight landing situation. - Arheo

Oh my days...


Supply is actually going to be in this game now. I just wonder how difficult it is going to be to build trucks as a trade off. Everyone had donkeys and horsy boys when transporting supplies.
 
Not atm, we felt it probably isnt worth the complexity
To echo at least half a dozen other people, it's worth the complexity. Please reconsider if it's at all feasible to implement fuel consumption by supply trucks.

Yeas, impliment scorched earth tactics when you retreat, just wrecking infrastructure, industry, everything

This is an example of Raildestruction
Perhaps lock scorched earth tactics behind the Mass Assault doctrine and the Desperate Defense branch of Mobile Warfare? I'm not sure how that would feel for players or how many historical instances of scorched earth tactics it would prevent.

At the very least, if scorched earth tactics are added to the game, I think adding increases to their destructiveness to Desperate Defense and Mass Assault makes sense.

Ok, but why should converting soviet rail take longer than indian rail or Japanese rail or even chinese rail? There wasn't anything special about soviet rail, it was just a different gauge. There were many different rail gauges during the period and it would be more realistic and better for gameplay to just have a generic non core repair penalty.
I think the ideal solution would be to catalog the various rail gauges worldwide, assign a unique value to each, and calculate a binary cost for converting railroads based on whether a local gauge is different from your national gauge.

If you're fighting a civil war, presumably the railroads you're fighting over are all the same gauge and can be quickly integrated into your network; if you're invading the Soviet Union, integrating the conquered railroads will take longer.
 
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That’s what I thought the trade off might be... Ive got one petrol can but who do I give the fuel to. I’ve got a soviet company running over the hill at me along with armour.

Do I fill my Panzer up so he can go into action or do I fill a truck up with fuel to ensure my infantry has enough ammunition.

The horse would take too long and not provide adequate supplies. Ammunition Supplies have already been delivered for my Panzer on the previous can.

If you get what I mean...
 
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For sake god, tricks don't using fuel again? Really, really? We have years of discussion about it, the key feature of one of the biggest update was fuel.
I can accept that they delay it for balancing in a post realise update as a fix of the scale of the work is so big, and it's. But don't do it again. There will be spams about this worst than Finland, because is worst...
 
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Can we expect the AI to use mulberry harbors on its own or will it remain something extremely rare, entirely impossible, or scripted forspecific situations for it ?
you mean like the way paratroopers are a player-only feature of the game, right? :)))
honestly tho, half of the dlc features of the game are handicapped by the meh ai
 
I get it’s going to add complexity to add fuel to trucks. If it cannot be done then don’t let the strategy of production... alone be the only impact.

Adding fuel to the game added the secondary problem of keeping produced machines actually moving. Maybe every truck you build has a negative effect on...something ... other than production (Do trains use fuel?)

Maybe we don’t know something yet for the future supply diaries.

Wishing you a great summer HOI4 team!
 
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