Hearts of Iron IV - 33rd Development Diary - Supply

[podcat]

Another Friday, another diary! Today we will be talking about something a lot of you have been asking about for a long time: The Supply System. This is going to be a big one!

The HOI3 supply system had a lot of problems. It was hard to understand how it worked, and it was hard to know what to do to solve supply problems for the player because it was usually due to missing something some time ago. We even made a separate Arcade Mode for supply which of course nobody used (what self respecting player would pick something called "Arcade Mode"?).

After a couple of glasses of 16yo Lagavulin and some deep thoughts the following problems needed to be solved:

• It must at any point be possible to look at an area and see how many troops can work there without problems. Also for naval invasions.
• It must be possible to see exactly what the bottleneck in your supplies are and give the player possible actions to fix this that are clear.
• The supply system itself must not have long complicated flow networks where cause and effect are hidden by time.
• The supply system must not collapse if a capital is taken which was a big problem in HOI3 and both unrealistic and not fun.
• Holding out in cities should be possible even when cut off from the rest of your force.
• Resistance must be able to hurt your supply lines without being a Whac-A-Mole problem.
• Supply issues need to get gradually worse for a unit rather than feel binary like in HOI3.

Scary list? Sure is, but I think we managed to solve all of it. So how does it work then?

• The world is separated up in Supply Areas, made up of provinces. They are purely for gameplay and generally follow terrain types and such.
• Each area can tell you at a glance exactly how many divisions it can support and how much you are taking up.
• If you hover your mouse over an area it will show you an arrow tracing the path supply takes, and indicate what is limiting it. Areas also have quick buttons for helping solve problems right there (improve naval base level or infrastructure etc).
• The game will show alerts from areas with supply problems to notify player (super useful when you are, say, Britain and spread over many theaters).

The supply level of an area are decided by the following things:

• A local scripted value. Think of it as base infrastructure that can't really be destroyed (will be basically 0 in mountains and deserts and pretty high in densely populated Europe).
• Any big cities/victory points will increase it. So holding out in these is possible.
• Local resistance movement activity in occupied territory disrupting things for you (we'll have a separate diary on these guys)
• Incoming supplies from neighbor area. We trace back to capital, or if capital is cut off the next best area. The supply you get is limited by the lowest infrastructure on your route (also possibly sabotaged by resistance), including your own infrastructure level. So for a player what you need to care about is what the bottleneck is, because that is what is going to affect how troops on the front fare. There is also some guaranteed spillover from neighbors to soften the transitions between bad and good areas (simulating that even if decent railway lines stop at a point it's feasible to transport some distance with trucks or horses etc).
• If we are cut off from home area, say fighting in Africa, or on an island, supply will travel overseas using convoys and be limited by the size of the ports receiving it. So making sure convoys are not sunk and bases are able to sustain you is important before doing any overseas activities.
• Put transport planes on a mission to drop supplies. Useful for cut off troops (this is still WIP so can't show it yet).
• It also worth noting that supply areas will change size if they are being fought over so actual levels will depend on how much you control.

When a unit finds itself out of supply it has a short period of time where they can live off their own supplies, after that their situation will gradually get worse up to about 30 days when things get very bad. Being out of supply makes you lose organization, move slower, not fight as effectively and take a lot more attrition. Veteran players of HOI know that the best way to beat the enemy is to cut off their supply, encircle them and then destroy them, and this remains true in HOI4.

So how can a player improve their supply situation?
You start by finding the bottleneck.

• Improve infrastructure to allow more supply into the area.
• If linked by sea, make sure to escort convoys and protect them from raiders.
• Build bigger naval bases to allow better throughput.
• Deal with local resistance.
• Research and attach Supply Companies to your division templates to help them manage.
• Airdrop supplies.
• Simply withdraw some troops from an area.

So, what is supply exactly?
In HOI3 supplies was something you produced and stockpiled, then fed into a flow network towards units. In HOI4 the only thing you can stockpile is equipment so this is what you do. Moving, training, fighting, being in bad weather or in particular in bad supply means equipment breaks down and this equipment needs to be shipped. The worse a supply situation is the longer it will take to send equipment and the more attrition you will take. So instead of a flow network we have a system being limited by bottlenecks.

So this means that the abstract "supply" of HOI3 is now instead requests for specific equipment instead which fits a lot better in with HOI4's equipment and production focus. This also means that there is no separate fuel need as such in the game, this instead is included in production of replacement equipment which need Oil (all tanks, trucks etc). Before everyone chokes on their friday beer give this some thought. Being able to stockpile fuel generally leads to the same problems as all other kinds of stockpiling when it comes to hindsight, so by wrapping it into the actual production of equipment requests to units (also nobody would request a tank without diesel to run it, and if they did it wouldn't really be usable as a tank) everything clicks into place and player doesn't have to micro manage all movement, airplane rebasing etc to try to avoid fuel waste and focus on making sure they have access to a strategic Oil resource and replacement equipment and a clear path for units to be supplied.

(p.s dont look too much at the numbers in all these screenshots, we havent really finished balancing supply yet)

Next diary we will take a look at civil wars and coups!

 

[podcat]

Very good improvment

Question: are aircrafts now transported by the logistical network?

No, a bit too complicated to manage, but their bases ties into the supply system so you need supply to run missions from the area

That dog on the bottom right in the last picture, lolwhat

its our developer debug mode dog that barks when we get errors in our error log

This is probably one of the best changes I've seen from 3 to 4.

+1

Thanks!

 

[podcat]

Equipment are supplies now, no more generic supplies which are probably the best thing of this DD

yeah, which means that *how* to supply someone becomes more important. If you lose some resource you need (say chromium for advanced tanks) you might have to reoganize those divisions to be able to supply them.

Its a massive buff to the Japanese navy

yes this is a downside from a pure simulation perspective in that they can be more active. its also a buff to fun since you dont have to stick them in a port the whoel game. They still have the same issues as historical though: A desperate need for oil to replace lost ships and build a big enough navy to fight USA (USA can affort do lose ships, japan really can't since they take so long to build).

 

[podcat]

Possible to get a specific on what:Required exactly means? I know supported means how many can stay there and incoming is how many you have entering the province, but what the required is what I am not sure about.

Required is what the units stationed there needs. Units need more when fighting for example. A supply need of "1" is an average triangular infantry division without a supply company for reference, so if you build hungrier divisions thats what you can compare on. The division designer will tell you what the requirements will be when you adjust templates.

 

[podcat]

Awesome, looks fantastic! Some questions. In the first screen shot it looks like the Japanese don't have a convoy route to Korea and was curious about that. Secondly do you have control over your supply routes or is it completely automated? Lastly I assume you still need oil to produce supply for motorized equipment or am I wrong about that.

Routes are automated and I think someone might have put a strait to korea from back when we were testing stuff, should probably remove that. And yes motorized equipment requires oil of course.

Wow, another fantastic DD with all the right solutions to complex problems.

One question:
The Allies have 20 divisions on some island. Local supply is enough for 5. I go all-out submarine on them and eliminate convoys entirely.
What happens? Will all 20 divs gradually be reduced to 25% strength?
Is it possible to build up local infrastructure to supply all 20 units despite being completely cut off from naval supplies? Sure it'd be costly and should take a long time, but possible?
I'm already contemplating a proper U-Boat campaign to starve the enemies' troops overseas.

Bumping local infra will not help you if you are cut off completely (neither will boosting the naval base if enemy subs sink 100% of incoming transports), if there is no local victory point or base supply you will slowly starve.

fighting does not impact the supply requirement as far as i understand it

fighting increases it

 

[Mrop]

I see the Japanese are launching a "supplies attack".

 

[podcat]

That was not what Podcat said last june in a thread about splitting and merging divisions.




That statement seems to validate dizzle3 assumption.

Even if you get the equipment you will still not be in supply, we track supply status too, it isnt JUST equipment you currently have

@Keyenes2.0 the size thing are only for some stuff, because yes otherwise it can become a problem