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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 don't you just make supplies produced by a certain number of civ factories instead of getting them from nowhere

This was how it was done in every HOI until 4.
 
Scorched earth was almost universal to some extent. For instance the British when in retreat in north africa dumped thousands upon thousands of gallons of fuel into the sand rather than allow Axis forces to capture fuel. It wasn't a doctrine choice as much as not giving equipment or fuel to the enemy.

That was a theatre where everyone was in short supply.

Once again fuel is half of supply.

The other half I guess were trucks and ammo carriers. Which were basically tank chassis without a gun. And in some cases when they had attrition, they would turn the ammo carriers into functional SPGs.
Yeah. That's probably why it's not in the game: if everyone engaged in scorched earth historically and it's always beneficial to do so, then there's no thought or fun involved in choosing when and where to do it.

Desperate Defense and Mass Mobilization already unlock guerrilla tactics and increase damage to enemy garrisons, so I suppose my suggestion is implemented to the extent it can be.
 
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Yeah. That's probably why it's not in the game: if everyone engaged in scorched earth historically and it's always beneficial to do so, then there's no thought or fun involved in choosing when and where to do it.

Desperate Defense and Mass Mobilization already unlock guerrilla tactics and increase damage to enemy garrisons, so I suppose my suggestion is implemented to the extent it can be.
Well there is a choice...in the face of a superior enemy, do you withdraw your stockpiles or leave them there to the last minute then destroy them?

It's a little bit complicated. But it's sort of a double edged sword because by not reinforcing and resupplying fortifications, supply hubs etc, they become much harder to hold on to. Or so I heard. Same example of the British now finding retreat a self fulfilling prophecy of sorts because they are just not supplied to react defensively.

Because the issue of capture and loss is a strategic one.

Like would we rather give guns supply and fuel to the enemy or have the needed materiel to forcefully repel an attack? Because if you discard your own supply or withdraw it then you basically sabotage the enemy and your front line or garrison troop.

But I do think just like withdrawing armies, you would withdraw your supply system. But doing so is also not good while you are still there.
 
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Let us remember that the German industry could not satisfy and build the necessary trucks to supply their army in a total motorization except for a few divisions there that will massively use horses or trucks from other occupied countries totally different from there they had serious spare parts problem Necessary of this imported models that were not standardized in the German army

Not only, the lack of oil also cause a dramatic lack of industrial lubricant which have big impact on axis industries.
I feel that oil is practically useless in the actual state of the game and it make little sad.
 
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Yes of course

If Railroads can be build , they can be destroyed,too.

Check out the : "Railroad Plough" it lowers the Railroad to 0.0 very fast . But it need to be invented first and this should be integrated into the next dlc


yes for Railroad plough
in german language its called: "Schienenwolf" see picture below.


The main Problem for USSR /axis railways are thery dont fit to each other. USSR using

Broad-gauge railway​

1,524 mm
while rest of EU territorry using

Standard-gauge railway​

1435 mm
that would mean no train of axis could drive on USSR trains while USSR trains cant be used in western territory

Bundesarchiv_Bild_101I-279-0901-31,_Russland,_Einsatz_des_'Schienenwolf'.jpg
 
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Most of this looks really nice! The only question lurking in my mind is why there still needs to be a "supply capital"?? You have a supply cap dependent on industrialisation (excellent! - would be even better if the % used reduced the production capacity of the industry a bit... ;)) , so why not have this for each connected "set" of supply hubs? The problem of 'capital connections' then goes away completely; each connected "set" of hubs forms its own supply pool (I am assuming that both industry and supply hubs are connected to states - industry already is, and it would seem logical for hubs to be, also).

On the topic of railway conversion times - could this perhaps be done with a state flag? Each country would then have a 'standard', and converting would have a time modifier if the flag is "wrong" (and the flag would be set to the new country standard when converted). The application of flags could even be done by a starting event, to save on state scripting.

Edit to say: Could it also be possible to have the facility (at a cost) to "supercharge" a hub ready for a major offensive? The idea would be to "discharge" the hub, giving bonuses to units drawing supply there for a period of time (when the "charge" runs out and must be built again before the same effect can be gained).
 
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I like how this is shaping up.

One disappointment for me though is the first screenshot shows the issue of Romania occupying half of the Eastern Front territory in its own right is still a thing.

I just find it very unrealistic and wish the AI would just transfer the provinces to Germany.
 
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The Devs are very aware of the cheater problems, that is why they already tried fixing it in a hotfix in the last few months.

But cheater got smarter and send commands that are extremly hard to detect invalid for the game. Especially since the main goal of Multiplayer at release was ease of use and not security.
Right - the best way would be to identify the cheats and send them to the Eastern Front. How far East? I think the dark side of the moon at sunrise should be far enough...
 
The Soviet union and China already have decisions to destroy their countries infrastructure, its burned earth for the Soviets and flooding for the Chinese, but I think these decisions should be made generic, maybe spend some PP and CP and then destroy a province's infrastructure through a decision. Especially for the German retreat to the Panther–Wotan line this could be interesting.
Another question is whether or not partisans will destroy trucks used for supply, I presume so but their effect on trucks and trains hasn't been explained yet.
 
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Should be mills
Civs should be involved, too; I think the best measure would be 1 MIL + 1 CIV --> X land/air unit supply, 1 NAV + 1 CIV --> Y naval unit supply.
 
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I'd rather not have railways where there were only pipelines. I don't really see the point in pipelines tbh. Those that come to my mind are situated in a way that makes them not really targets at least in the Middle East. Any invader making it as as far as Haifa will most likely also make it to Kirkurk to take the oilfields. If not oil would be shipped down the rivers, so they are a bit pointless.
I think the point might be more about the fuel pipelines used to supply Fighter Command bases (and other RAF bases, too, actually) in the UK and similar. These might be part of the infrastructure when local, but also abstracted as part of the rail level for longer distances.
 
I think it is amazing, whatever the developers want to do with the game there are always demands for even more detailed realism

Correct me if I'm wrong, but I believe it was said in an earlier diary thread that they skip fuel consumption for supply trucks because it would require too much work and time to balance it right. And the AI would probably not "understand" how to handle it anyway.

Hopefully modders who have more time to spare than the devs can experiment with fuel consumption
 
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Yes of course

If Railroads can be build , they can be destroyed,too.

Check out the : "Railroad Plough" it lowers the Railroad to 0.0 very fast . But it need to be invented first and this should be integrated into the next dlc
The way I understand it, scorched earth tactics like this is part of the time delay we're already getting to getting railroads up to full capacity.

Perhaps techs like Railroad Plows could increase the time it took for the enemy to restore railways, though?
 
1 MIL + 1 CIV --> X land/air unit supply, 1 NAV + 1 CIV --> Y naval unit supply.
Hmmmm.... maybe a "quick & dirty" abstraction would be to remove factories based on the military size.

Something like ...

IF # of Divisions > 50 disable 1 MIL and 1 CIV
IF # of Divisions > 100 disable 2 MIL and 2 CIV
IF # of Divisions > 150 disable 3 MIL and 3 CIV
etc, etc.

The only question lurking in my mind is why there still needs to be a "supply capital"??
Agree. But so many other changes, making any change to the "supply capital" concept was probably rejected because of the possibility of introducing new bugs. Maybe with some tweaks, we can get multiple supply capitals.
 
The main Problem for USSR /axis railways are thery dont fit to each other. USSR using

Broad-gauge railway​

1,524 mm
while rest of EU territorry using

Standard-gauge railway​

1435 mm
that would mean no train of axis could drive on USSR trains while USSR trains cant be used in western territory
Not as bad as "no train could drive". It's an issue of changing bogies at the place where two gauges meet. For example nowadays Moscow-Berlin express train gets its bogies changed at Brest-Tarnopol in less than 1 hour.

Manufacturing or otherwise acquiring necessary bogies as well as equipment and rail spurs and personnel for their change can of course be costly.

I don't know history of Reichsbahn at all, but for some reason during WW2 Germans decided to change gauge of railways track in occupied areas of Russia rather than create bogie-change stations and assets. IMO it was a stupid decision - it looks much easier to me to create 5-10 stations way behind front lines and change bogies there rather than re-lay thousands of kilometres of rail track in bad weather (plus you get to use all captured rail transport without alterations). Maybe someone who is more knowledgeable on this can comment why Germans went this way and not the other.