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HOI4 Dev Diary - Traiiiiins

Greetings, and welcome back for our last look at the supply system that ships with the Barbarossa update. As you all know, I’m British, and in Britain the trains never run on time - I couldn’t possibly break with this tradition, hence a completely intentional 10 minute delay on today’s diary.

There’ve been a couple of changes since we last looked at this, so you may find I’ll be reiterating a few aspects that we’ve already covered in previous diaries, albeit in some cases with a new twist.

Trains

As indicated in a previous diary, the logistics network that supplies your troops relies on the large-scale relocation of supply using trucks and trains.

Whereas trucks serve as an optional last-mile carrier for military supplies, trains make up the backbone of any logistics network that supplies an army which exceeds the local state supply available in its location.

The domestic production of trains is something that is unlocked via the technology tree. Many countries will start with the initial (civilian) train technology readily unlocked, however, there are several more options available to you as time progresses (more on this below!).

0.png


Your overall train need for the logistics network is derived from the overall supply usage of the nodes supplying your troops, and the distance factor that supply has to travel in order to reach them. In essence, the more troops you have drawing supply, the more trains you will need to keep supply running.

Needless to say, if fewer trains are provided than are required, supply output at point of demand will incur penalties proportional to the magnitude of the shortfall.

In one of our previous diaries, we alluded to a number of interactions that could be performed on supply nodes - one of these was a train priority setting. It transpired that this did not fit well with the underlying simulation, and we’ve removed this setting from nodes.

Logistics Strike

Of course, a freight-train loaded with supply makes a juicy target for the enemy. In NSB, CAS and bombers are able to perform the new logistics strike mission, which can put a severe strain on an enemy’s ability to supply their network - actively destroying trains and trucks, as well as damaging railways in the target area.

The strategic bombing air mission will also target rail and supply infrastructure, however the logistics strike mission is a much more effective way of neutralizing an enemy’s fighting capabilities while retaining important industrial infrastructure if you intend to occupy an area for any period of time.


1.png


Train Variants

As mentioned above, trains will be a researchable technology with several variants. Trains, unlike regular units, are not controllable - their movement and behaviour is entirely simulated based on the needs of your logistics flow. This said, there are several important statistical aspects to them.

2.png


To begin with, most of your network is likely to be populated by civilian trains. You can construct more of these by co-opting military factories. Further on in your campaign, you can unlock a variant of the civilian train with a significantly reduced construction cost.

To combat the strategic mission mentioned above, there is one (or..is it more?) further item in your toolbox for owners of the NSB expansion. Armored trains, while coming with a higher price tag, are much more resistant to destruction from air missions, and can act as an effective deterrent against logistics disruption.

Train enthusiasts (we have none of those here, right?) will note that the trains displayed above belong to the soviet union - there is indeed unique art as well as 3d models for several other major nations.

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A highly camouflaged train in action.

7.png

Displayed trains are based on your stockpiled train equipment. This is the german armoured locomotive!

That’s all from me for today - I’ll hand over here to @YaBoy_Bobby to go over some of the details on supply distribution at a hub level:

Hub to Province Supply Distribution

We have talked about how trains and rails feed the supply hubs, but not so much about how hubs feed divisions in the field. As hubs are fed from the capital province by a rail network, divisions are fed by hubs over land.

Every Hub has an overland range that gives it a collection of provinces that it touches. This range is constant, but the cost of moving over each province is impacted by things like weather, terrain, rivers, and infrastructure. Motorization decreases the penalty for crossing each province, thus increasing the number of provinces a hub will touch and potentially creating greater hub density and thus greater overall supply in an area.

8.png


As has been alluded to with the phrase “hub density,” a province may be touched by multiple hubs. When multiple hubs touch a province, a ratio is created to determine what percentage of the supply requested each hub is responsible for. Every hub that touches a province lessens the supply burden of other hubs also touching the province.

In the final step, Divisions draw supply from hubs, depending upon the relationship between their current province and the hubs that touch that province. When a hub does not have enough supply to meet demands, the lack of supply is distributed evenly across all divisions currently drawing from the hub.

In older DDs we talked about a penalty to the amount of supply delivered to a province based upon weather, terrain, and distance. Over the summer we decided to remove this penalty as we found it compounded in a hard to predict way that created bad supply and sometimes penalized having more hubs touching a province in a way that we did not like.
 
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In older DDs we talked about a penalty to the amount of supply delivered to a province based upon weather, terrain, and distance. Over the summer we decided to remove this penalty as we found it compounded in a hard to predict way that created bad supply and sometimes penalized having more hubs touching a province in a way that we did not like.

This... sounds a bit odd. Is the penalty to supply from weather, terrain and distance gone entirely - or is it how the penalties interact with hubs that touch more provinces that has been changed?
 
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We better be able to use subterfuge; partisans, to derail trains behind enemy lines! On the Eastern front, that was particularly pronounced activity by the partisans in German occupied territory. If not, it will be a colossal missed opportunity.
There was also a train wreck in the US where the cause was never determined. Many, my father included, believe it was German sabotage.
 
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There was also a train wreck in the US where the cause was never determined. Many, my father included, believe it was German sabotage.
I would like to hear more about this
 
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No actually. The thing about Mussolini "making the trains run on time" is that he didnt. At no point did he really succeed at making them run faster. What he actually did was have the train schedule adjusted so that the schedule arrival time was the time the trains were usually late by. Innother words, he half-assed it and just declared the delays as being "on-time" instead of actually trying to get the trains to meet it.

Um....welcome to being Germany during WW2. That was something Germany had to face constantly during WW2 and they were never able to stop them even 50%. I see no reason for why the devs should make the AI not make you have to defend German Airspace. If you are having issues and cant spare more fighters, build more static AA and never used concentrated industry, and defeat Russia, so you can actually focus your aircraft on the west.

Totally missed the point of my post, but thanks for your amazing history lesson and gameplay tips lmfao very deep level stuff
 
Hello.

As you overhaul supply system, have you considered adding fleet oilers/supply ships to supply ships on ongoing missions? Right now fleets can stay indefinitely on sea, without going to port for refuelling/resupplying, bar aside visiting port for repairs.
Overall very good dev diary and can't wait for new system when its finally released!
 
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They performed a test three years later, showing just how difficult it is to derail a train, giving support to the theory:
That study they should have done with European trains. Unlike American trains, these normally had only two axles and less stiffness in the couplings.
 
As you overhaul supply system, have you considered adding fleet oilers/supply ships to supply ships on ongoing missions? Right now fleets can stay indefinitely on sea, without going to port for refuelling/resupplying, bar aside visiting port for repairs.
Adding fleet oilers/supply ships would mean naval fleets would have to return to port unless they had those oilers/supply ships. I'm not sure if anyone other than Britain, US and Japan where equipped like that.

You are correct that it is more realistic. But is the change to all fleets returning to ports worth the effort of change at this point?

Maybe an alternative is to assume the fleet fuel requirements are those oilers/supply ships, with a cost in convoy ships. Personally, I keep my minors fleets at home (on strike orders) cause I don't want to burn the fuel. An abstraction representing my lack of oilers/supply convoys?
 
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Little question about the taking over of rail networks:
How will you manage the lack of rails between some area? I don't think there was any railway between the USSR and Germany, does that mean you will have to either construct it or make some sort of relay with motorised? there is another thing I though about, how will you emulate the fact that different countries used different distance inbetween the rails of their railways? Is it part of the "adaptation" time after taking over a suply point or would it need additional work via the construction pannel? I am asking this as, if i recall it right, I think germany and the soviets did had troubles because each-other's trains were not fit to move on the other's railways, making it a bit harder too to bring suply.
 
In older DDs we talked about a penalty to the amount of supply delivered to a province based upon weather, terrain, and distance. Over the summer we decided to remove this penalty as we found it compounded in a hard to predict way that created bad supply and sometimes penalized having more hubs touching a province in a way that we did not like.
This is what happens on real railways, a problem in one place will cause nock on effects in others often far away and seemingly unconnected places, its a Feature not a Bug!!
 
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The BR 18 doesnt fit the german cargo lokomotive. I pressume from the picture and the name that you choose a bavarian locomotive that was for fast passenger transport not cargo transport. A replacement would be the BR 44 which was produced from 1926 to 1949. Maybe you could rename the german war locomotive into BR50/ BR52 because the BR50 wich entered service in 1939 was designed with a war in mind and the production switched gradually from BR 50 to BR 52. Both locomotives had a great deal of common parts plus there was a so calle BR 50 ÜK which was the step between BR 50 and BR52.

Will ships be able bombard infrastructure too?
 
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Greetings, and welcome back for our last look at the supply system that ships with the Barbarossa update. As you all know, I’m British, and in Britain the trains never run on time - I couldn’t possibly break with this tradition, hence a completely intentional 10 minute delay on today’s diary.

There’ve been a couple of changes since we last looked at this, so you may find I’ll be reiterating a few aspects that we’ve already covered in previous diaries, albeit in some cases with a new twist.

Trains

As indicated in a previous diary, the logistics network that supplies your troops relies on the large-scale relocation of supply using trucks and trains.

Whereas trucks serve as an optional last-mile carrier for military supplies, trains make up the backbone of any logistics network that supplies an army which exceeds the local state supply available in its location.

The domestic production of trains is something that is unlocked via the technology tree. Many countries will start with the initial (civilian) train technology readily unlocked, however, there are several more options available to you as time progresses (more on this below!).

View attachment 752460

Your overall train need for the logistics network is derived from the overall supply usage of the nodes supplying your troops, and the distance factor that supply has to travel in order to reach them. In essence, the more troops you have drawing supply, the more trains you will need to keep supply running.

Needless to say, if fewer trains are provided than are required, supply output at point of demand will incur penalties proportional to the magnitude of the shortfall.

In one of our previous diaries, we alluded to a number of interactions that could be performed on supply nodes - one of these was a train priority setting. It transpired that this did not fit well with the underlying simulation, and we’ve removed this setting from nodes.

Logistics Strike

Of course, a freight-train loaded with supply makes a juicy target for the enemy. In NSB, CAS and bombers are able to perform the new logistics strike mission, which can put a severe strain on an enemy’s ability to supply their network - actively destroying trains and trucks, as well as damaging railways in the target area.

The strategic bombing air mission will also target rail and supply infrastructure, however the logistics strike mission is a much more effective way of neutralizing an enemy’s fighting capabilities while retaining important industrial infrastructure if you intend to occupy an area for any period of time.


View attachment 752461

Train Variants

As mentioned above, trains will be a researchable technology with several variants. Trains, unlike regular units, are not controllable - their movement and behaviour is entirely simulated based on the needs of your logistics flow. This said, there are several important statistical aspects to them.

View attachment 752462

To begin with, most of your network is likely to be populated by civilian trains. You can construct more of these by co-opting military factories. Further on in your campaign, you can unlock a variant of the civilian train with a significantly reduced construction cost.

To combat the strategic mission mentioned above, there is one (or..is it more?) further item in your toolbox for owners of the NSB expansion. Armored trains, while coming with a higher price tag, are much more resistant to destruction from air missions, and can act as an effective deterrent against logistics disruption.

Train enthusiasts (we have none of those here, right?) will note that the trains displayed above belong to the soviet union - there is indeed unique art as well as 3d models for several other major nations.

View attachment 752463

View attachment 752464

View attachment 752465

View attachment 752466
A highly camouflaged train in action.

View attachment 752467
Displayed trains are based on your stockpiled train equipment. This is the german armoured locomotive!

That’s all from me for today - I’ll hand over here to @YaBoy_Bobby to go over some of the details on supply distribution at a hub level:

Hub to Province Supply Distribution

We have talked about how trains and rails feed the supply hubs, but not so much about how hubs feed divisions in the field. As hubs are fed from the capital province by a rail network, divisions are fed by hubs over land.

Every Hub has an overland range that gives it a collection of provinces that it touches. This range is constant, but the cost of moving over each province is impacted by things like weather, terrain, rivers, and infrastructure. Motorization decreases the penalty for crossing each province, thus increasing the number of provinces a hub will touch and potentially creating greater hub density and thus greater overall supply in an area.

View attachment 752468

As has been alluded to with the phrase “hub density,” a province may be touched by multiple hubs. When multiple hubs touch a province, a ratio is created to determine what percentage of the supply requested each hub is responsible for. Every hub that touches a province lessens the supply burden of other hubs also touching the province.

In the final step, Divisions draw supply from hubs, depending upon the relationship between their current province and the hubs that touch that province. When a hub does not have enough supply to meet demands, the lack of supply is distributed evenly across all divisions currently drawing from the hub.

In older DDs we talked about a penalty to the amount of supply delivered to a province based upon weather, terrain, and distance. Over the summer we decided to remove this penalty as we found it compounded in a hard to predict way that created bad supply and sometimes penalized having more hubs touching a province in a way that we did not like.


1. How does AI handle the new logistics features? Can it deal with it?

2. Does the new DLC/Patch allow AI to build tanks? Since release, AI armies consist exclusively out of infantry and artillery. In the early game, they maybe have some light tanks, but once they research medium tanks, they stop using them. In every single game since release, I check the equipment of nations in 1945. And not once they had at least a tiny amount of tanks.
 
Did someone say TRAIN
 
So no penalty for supply delivery in the winter? Can this at least be modded?
The most important reason why Russia survived and ultimately won the war against Germany, can not be represented in the game. Neither is the reason for German agression, is all that presentable in the existing game mechanics. That is, almost a zealous religious commitment of the populace to the ideology in Germany and Russia, respectfully.
 
Hello.

As you overhaul supply system, have you considered adding fleet oilers/supply ships to supply ships on ongoing missions? Right now fleets can stay indefinitely on sea, without going to port for refuelling/resupplying, bar aside visiting port for repairs.
Overall very good dev diary and can't wait for new system when its finally released!
Yes, we totally agree that there is a naval resupply of supply, we remember this was vital in most oceans such as the Battle of the Atlantic, which were called by the Germans as the Dairy Cows.
 
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"Throughout the rest of Europe, including Germany, France and Poland, trains ran on tracks 4 feet 8½ inches wide, the so-called Standard Gauge, as they still do today. Thus, when Germany launched its blitzkrieg invasions, troops advancing into Poland and France could be supplied by German trains travelling across the border onto Polish and French railway lines. As luck would have it, however, Russian railway lines were a different width to the rest of Europe, 5 feet wide, as they still are today. As a result, German locomotives couldn’t cross the border from Poland to support and supply advancing German troops, which was a highly significant factor in the Nazi failure to rapidly capture Moscow before the onset of the freezing Russian winter."