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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!).

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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.


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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.

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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.

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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.

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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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Seems like quite a bit of stuff has been simplified from previous DD's

"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."

"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."

and armored trains are just harder to kill
 
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Really nice, but one question: the majors have their own train 3d models and 2d tech images, but can you give us a tease of the generic 3d model(s) and/or the generic train tech tree? That is, I mean, the generic used by all the other nations other than the big 7.
 
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I've got a question: which parts of the new supply system will come with the free update and which with the paid DLC?
Unless I`m missing something, the only shown part of the supply system that comes only with the paid DLC is the new Logistic Strike air mission, the armoured trains and the Mulberry Harbors. Everything else should come with the free Barbarossa update
 
Hey,
I wanted to ask about railway construction - in a prior dev diary the rail and supply hub construction was located in the 'province' building section with land forts instead of with infrastructure at the state level. Does that mean we will need to build a railway on every province from lets say capital to front line? Or does every nation with large distances already have railways pre-built in 1936?

Also can supply hubs, if at a province level, can they be built on any tile - or only on victory points? Because I'm imagining building a supply hub on every province being some cheese at some point haha.

I guess while Im here Ill also ask if theres any posibility of there being a Don Cossack Republic to add to the great mix of releaseables that came with the Soviet Union - it was a highly requested nation with direct ties to anti bolshevik uprising. Anyways, good dev diary!
 
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Will you be able to transfer troops using trains or it will just influence their speed? My Siberian reinforcements might not arrive on time to save Moscow.
 
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They are harder to kill. If you can convince the enemy to form a large line on a train track, you may have a good use case for offensive train warfare... but in HoI - nope.
Armoured trains were in fact used by essentially all countries fighting in the war and to some good effect. Poland if famous for it's extensive use of armoured trains during the German invasion and there are actual battles specifically against armoured trains. They could be used to great effect in the early war since they could be better armoured and use bigger guns than most tanks in use and you really would have a bad day trying to attack a proper armoured train with panzer I or II. Russia also had a large number of such armoured trains but it lost most of them early on for rather obvious reasons.
I would say it is enough to give it some representation in HOI4.
And to add to the point I think it would be good to make armoured trains at least have some effect on enemy air operations in a given strategic region, some of these trains were specially made for anti-air service and it would be interesting if they had a effect similar to some static AA even if a lot smaller. At minimum they should be able to deal some damage to enemy planes on strategic bombing/logistical strike missions or to give some AA value when a battle is fought on or near a railway operating a armoured train.
 
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How moddable is this system? Can we add other equipment or elements (say, I dunno, fuel) besides trucks to the system?
 
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I wonder if we can now "sink" a train by naval bombardment. Something of that sort happened in Japan, with USS Barb, a submarine, landing 8 of her sailors to place demolition charges on a railway bridge and thus "sinking" a train that passed over the bridge!
 
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Would you say we are getting close to release? What else is there to show? It seems like all of the major features have been covered.
I assume a release late october is quite likely, since they have to coordinate the launch window with the CK3 Royal Court DLC also coming this year. The Royal Court DLC looks like a late November release at the moment, since the devs said that work on that is progressing slower than they hoped but it will release this year.
The HoI4 DLC has to release late october at the latest id say.
 
Well I wonder, it seems the current no air russia meta won't work anymore, if Axis CAS just can destroy all enemy trains.
Gonna be interesting.
 
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In which research section are trains located? Is it in the armored section? And what does the complete technology tree for trains look like, if not a secret? Great diary, by the way!
I would think they will get their own category, especially since doctrines are being moved out of the research tab and into your army academy/high command that's coming with the next update.
 
Is there going to be any changes on Japan focus tree regarding to that, supply going to be a huge issue in China and it will require massive railroad projects to win. You know like they did with POWs.
 
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