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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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Not sure exactly how to implement a railroad plow, to be honest. Perhaps it'd be best implemented as a tech that increased damage to railroads you lose to the enemy.
 
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The AI can possibly use the Feature that denies allies from using their supply e.g. france can deny america to let them use the supply in northern france
The only counter to this is that feature was mainly designed for the player to use. I don't expect the AI to properly know how to use it.
 
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Not sure exactly how to implement a railroad plow, to be honest. Perhaps it'd be best implemented as a tech that increased damage to railroads you lose to the enemy.
I do not think that a specific railway is needed for that purpose, it could be implemented with some new type of mechanics in the tab of the province that we remain and it could have a small regressive counter to be able to destroy infrastructure, forts or any other installation that the province has
 
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and the USSR in 36 for comparison (note the use of the river in the north)
Using the rivers for logistic seems very good idea. I hope this 'north river' is just example. Do you plan to use major rivers like Volga and Don for logistic?
Could you please add railroad line between Vologda and Arkhangelsk? This line was operational in 1936.
 
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WHERE IS TROTSKY'S ARMORED TRAIN ?
Considering it was disbanded and decommissioned soon after the Crimea campaign, its most likely in the scrap heap where it belongs.
 
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Minor gripe but;
Is there a particular reason the PRR L1s was chosen in the US tech tree over, say a PRR M1 or L1sa?
I'm pretty sure the screeny shows a PRR I1s, not an L1s. And they probably picked it because it 'They were the dominant freight locomotive on the system until World War II' (at least according to the wiki).
 
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Are troop movements effected by the new supply system? like no strategic relocation without trains or slowed movement on supply bottlenecks (since the rails and streets are already full with vehicles)?
 
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I'm pretty sure the screeny shows a PRR I1s, not an L1s. And they probably picked it because it 'They were the dominant freight locomotive on the system until World War II' (at least according to the wiki).
thank you, that makes more sense, I always get the two confused (doesn't help some people write L1s in lowerclase)
 
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As C0RAX showed, there were lots of trains shipped all over the place - the USSR got great benefit from lend-lease trains, is probably the single biggest example.
Yep. A lot of Soviet logistical equipment were actually delivered by LL, over a two thirds of the total trucks used by the Red Army in the war were foreign made including 409,000 cargo trucks and 47,000 Willys Jeeps, and more or less 12,000 locomotives and railcars were also delivered from 1942 onwards. LL was so vital to the war effort that Spam became a household name long after the war ended, and the Studebaker reached legendary status amongst Red Army veterans and was the inspiration for the newer Soviet truck models made after the war.

Not sure exactly how to implement a railroad plow, to be honest. Perhaps it'd be best implemented as a tech that increased damage to railroads you lose to the enemy.
You can implement it using decisions when your territory is being held by the enemy, or just raise resistance values and have them sabotage railways and supply hubs. Wouldn't work on occupiers losing occupied land though.
 
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Wonderful - sensational post Idle America :) Evidence of idleness is lacking!
I'm still proud of myself for coming up with that joke in middle school, as a reference to America not wanting to get involved in the war... and a pun on "American Idol."

Also, more train-on-ship porn? You're a man after my own heart!
 
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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.
 
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You can implement it using decisions when your territory is being held by the enemy, or just raise resistance values and have them sabotage railways and supply hubs. Wouldn't work on occupiers losing occupied land though.
If you have already lost the territory, how are you going to destroy the tracks...you would need to do it before (or while) you retreat.
 
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If you have already lost the territory, how are you going to destroy the tracks...you would need to do it before (or while) you retreat.
During the WW2, in the Great Patriotic War (Russian portion of the war against Germany) in particular, operations against German supply lines where systemic and on massive scale. Russian airforce would make daily delivery of military dynamite to the partisans in airdrops across the entire occupied Russian territory. We talking in tons. The effect was staggering, forcing Germany to abandon entire operations or delay those for extended periods of time. While, ultimately, those operations where not decisive for Russian success in overall war effort, it is estimated, the difference is counted in millions of lives Russia didn't have to sacrifice to achieve victory, and shortening of the war, by as much as 6 to 10 months of operations.
 
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During the WW2, in the Great Patriotic War (Russian portion of the war against Germany) in particular, operations against German supply lines where systemic and on massive scale. Russian airforce would make daily delivery of military dynamite to the partisans in airdrops across the entire occupied Russian territory. We talking in tons. The effect was staggering, forcing Germany to abandon entire operations or delay those for extended periods of time. While, ultimately, those operations where not decisive for Russian success in overall war effort, it is estimated, the difference is counted in millions of lives Russia didn't have to sacrifice to achieve victory, and shortening of the war, by as much as 6 to 10 months of operations.
Except that the statement that I quoted (and replied to) was concerning the use of Railroad Plows...not something that you could use after you had already lost the territory.
 
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PLEASE TRAIN!
CHOO CHOO YEAH!
WITHOUT RAILS!

*Absolutely slapping music continues on to the verse*


(I do hope I've not mistaken this as a reference, else this will be very awkward :p)
Finally someone who understands my reference throughout the two train-related devdiaries. Glad to see a fellow traveler here.
 
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The loss of terrain and weather effects is disappointing. Hope you guys add them back in.

Still looking forward to the patch.
 
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