Impedimenta: Feeding the Iron Behemoth - Logistics & Supply in Hearts of Iron

By Jeff Renaud 22 Sep 2016 0

Hearts of Iron (HoI), has been acclaimed as one of the first World War II PC games of grand strategic scope. It certainly was the first I’d ever played with a deep logistical system alongside robust diplomacy, a detailed technological model, and the opportunity to conduct global theatre-level warfare. Since we’re dealing with a game, however – especially a game as vast in scope as HoI – abstraction is also necessitated where gameplay would otherwise be over-complicated or compromised. So, how well did previous entries in the series deal with logistics and supply, especially in comparison to its latest incarnation, Hearts of Iron IV?

To start, it should be noted that Fuel/Oil has always been a separately tracked though integral part of ‘supply’ in HoI – albeit until IV, that is; more later. Otherwise, at the consumer end-point of its ‘supply chain’, the HoI unit – usually a wing, ‘fleet’, or division-sized entity – draws a certain amount of supply/oil/fuel from a national pool. Along the line, many factors impinge upon the exact amount a given unit receives, as well as how much is actually drawn from said pool (the difference being wastage or ‘overhead’, something not contemplated in all games; chiefly II). Foremost among these include infrastructure and distance from a supply head – either a naval port or the capital. Many other situations influence the calculation, such as whether or not a unit is stationary or in combat (and possibly receiving increased supply for offensive manoeuvres), nearby enemy activity – partisan or air/naval interdiction – in addition to the size of the depot. At one time or currently, even more abstract factors further modified a unit’s supply status, i.e. the difficulty setting, ministers, generals, redeploying units, or even new naval/air bases still awaiting deployment (where, pray, are they being ‘held’?).

Originally, the game tied Supply to a slider alongside Consumer Goods, Research, and Production; adjusting one of these four systems affected all others unless locked. In HoI II, Industrial Capacity abstractedly determined Transport Capacity, and was severed from other components while still modified by various factors mentioned above, ending up with Effective Supply Efficiency. In III, the sliders returned, now totalling five: Upgrades, Reinforcement, Production, and Consumer Goods (re)joined Supplies. Units ‘requested’ supply from a nation-wide network that had to be traced to a stockpile via a contiguous series of adjacent provinces or sea-zones; once found, supplies would ‘move’ one province/zone per day until they reached the requesting unit. Bottlenecks could form – and would be shown on the Supply mapmode – again due to various causes; more about bottlenecks in a bit. 

HOI3 Prod

My advice to you, monsieur, is to build more than one ship – les Boches sont à venir!


Back when HoI III players complained enough regarding the ease with which a German player, for example, could invade the U.S.A. through Canada or Mexico,version 1.06c imposed a heavy logistics penalty on invasions far from one’s capital: a rather abstract modifier of -66% to Supply Efficiency. While remaining essentially the same system, IV separates reinforcements – as well as intrinsic equipment – from supplies, and requires a valid supply route with at least 10% efficiency to send replacements. This calculation depends on port size and adequate convoys – more info here – but in any case, imposing the same penalty from III could have meant that overseas invasions might be nearly impossible to reinforce, depending on difficulty and other factors. Fortunately, that did not happen.

The main similarity between III and IV is that supplies are automatically convoyed overseas as required (assuming sufficient convoys); in the opinion of many players a very acceptable abstraction avoiding lots of micro-management. Additionally, supply capacity is tied to infrastructure in IV, but the main contrast is how the latter provides Local Supply to given areas of the map – usually two or more ‘states’; more about Local Supply later. Some further abstraction occurred where infrastructure is now averaged for each area, although now a depot’s capacity limits supply throughput; a small port will be very restrictive, a capital worth many VP (which add Supply Points) not much. Though still a rather esoteric – and mostly hidden – calculation, tooltips on the Supply mapmode (F4) can help identify bottlenecks (the big red arrow will be a clue!), which can then be theoretically corrected, e.g., by increasing port capacity and/or infrastructure.

Players whom have heretofore argued that the system ought to be more realistic, in that the actual supply situation should take precedence instead of levying an arbitrary stacking penalty or ‘distance’ modifier, as did HoI III, appear to have mostly gotten their wish, in some ways at least. The next questions are: 1) Does the AI understand it? 2) Does it actually work? According to this thread, opinions are mixed (on v1.1). I think only time will answer both queries, and more playtesting than I can do on my own prior to this article’s deadline. For now, I loaded a (1.2) game as Japan that I had been playing as Germany, just to check out the AI’s Chinese-Japanese War supply situation in a low-infrastructure environ. I didn’t see much that concerned me: In only one area the Japanese were undersupplied and in danger of being overrun. A couple of months later they launched an invasion behind the Chinese lines and seemed to be correcting the situation, but when I went back a month after that, they had been ousted from that beachhead. Yet, a few more months on, the PRC capitulated; China about a year later. What are we to make of this? 

HOI4 Japan Supply

Concerning, but not out of the ordinary.


As Patch 1.2 just released as this article went ‘to press’, it’s difficult to say definitively, especially since more will change with future patches and rumoured DLC. I can advise, however, that HoI IV players need be cognisant of the overall supply situation; current out of supply penalties are harsh. The wiki and various tutorials such as this short one and another, that also covers naval units and invasions, might help. It especially behoves players of island nations such as Japan and the U.K. to learn that trying to stuff 30 or 40 – or even far less – mechanised divisions into Africa or China before the infrastructure is in place to support them is likely to get them nowhere fast. Also note that I said before; planning to build improvements while attacking – or just prior – is almost as risky, since infrastructure and ports can be slower builds than you may want your troops to move.

This becomes a key strategy (or tactic; take your pick) for HoI IV players: Seizing enemy ports used for invasions will almost immediately cripple his supply effort (as mentioned in the linked tutorial videos). Not only ports, however; taking control of straits/canals will choke off supply as well, albeit do recall that VPs provide some Local Supply (and opinion is divided on the usefulness of the Convoy Raiding mission besides). Here, in my view – shared by others in the aforementioned Reddit thread – is where the system falters.

Local Supply often seems to enable what should be a doomed enemy to hold out almost indefinitely. (No wonder some of my – Germany’s – SCW interventions seem to be interminable!) Furthermore, the AI appears to choose some odd (inefficient) convoy routes. While I personally have no problem with having little or no control over routing – after all, the player is not omniscient and omnipresent – others do. In my own experience it has not been problematic, but then, I admit to ‘playtesting’ a lot – only as Germany, without trying any naval invasions to this point – and not yet getting a game into 1942 before I want to try something else a different way! 

900px Local supply map

It’s almost a Red sweep for Local Supply! (Source: HOI4 Wiki)


Bottom line? Other than the Local Supply issue – I side with players wanting to see some kind of ‘stockpile’ limit – and except for the navy and to a lesser extent the air force, I think the HoI IV supply & logistics system arguably works better than its antecedents, but it is almost totally abstracted – needlessly, I think. I am most chagrined to see that fuel/oil is no longer in the game other than to run factories. It just seems wrong to not factor in fuel consumption as an integral part of a comprehensive supply system for a game of this scale, and for the player to have no control over any of it save capturing provinces and improving infrastructure. (And I have not yet looked at air supply, which some players say doesn’t work in 1.1.)

Moreover, naval and air units’ supply usage seems miniscule, especially if it subsumes fuel: .01 for subs to .2 for battleships and .3 for fleet carriers (presumably including their aircraft complement). Aircraft seem to use around .1 to .2 for wings of 50-100 aircraft, but it’s hard to tell, as these figures are found on the unit Details window, when a fleet/aircraft is selected and a vessel or wing clicked on – which for the latter could be hundreds of individual planes. In comparison, the Supply Use of a typical 10-battalion motorised infantry division, consisting of a little more than twice a carrier’s Service Manpower of 5000-6000, consumes more than four times the supplies (1.3-ish). Is this reasonable? I admit to being unsure if it’s realistic, but in game terms, it seems… well, ‘gamey’.

These, then, are my chief beefs (ugh!) about the HoI IV supply system: Fuel, as an integral part of WWII-era warfare even on a lesser scale, is missing; Local Supply should not provide unlimited supplies for otherwise cut off defenders; plus the lack of player control/input into the supply system. To a lesser degree, air and naval units’ supply consumption seems too small if it includes fuel. (Moreover, aircraft and ships often appear to be drawing zero supply when the Supply mapmode is consulted; what’s up with that? Doubtless they aren’t on manoeuvres/patrol all the time, but…) 

HOI3 Germany Supply

Did HoI III get it almost right?


Again, the proverbial jury is still out on Patch 1.2, but here’s what I’d like to see fixed or ‘re-implemented’ for Patch 1.3 or later: 1) Add fuel consumption back into the game! I suspect such a change may be hard to effect now, though, so how about putting Supply Use on the Research screen for all units, instead of players having to memorise/calculate it themselves; perhaps worked into the Logistics window, as well?

2) Limit Supply Points (SP) for otherwise cut off units. It’s fine to factor in ‘bonus’ points for VP provinces – doubtless modelling the relative size of urban provinces – but either way they should not be unlimited. If a unit is isolated from its capital or a port, then SP in surrounding provinces should slowly dry up, until another depot is seized or a capital recaptured (unless blockaded – but that’s another article).

3) Perhaps along with #2, bring back supply ‘dumps’ from HoI III. In other words, supplies should move with the front; move them again a province-or-so a day, depending on infrastructure, and let them be captured as well (often a goal of certain combat missions; talk about immersion and realism!). Furthermore, while I hesitate to add complexity, what about a transport system of supply trucks, similar to supply convoys in previous games? Matter of fact, why was that taken out of the game in the first place? HoI IV supply and logistics has been abstracted to the point of starkness; all kinds of Support Equipment and Infantry Equipment is being generated, presumably including ‘bullets and bandages’, so, why not ‘beans’ too? And let me control it as part of Production (or optionally automate it as did HoI III via Arcade mode or AI Control). 

HOI2 Prod

…or maybe HoI II?

4) While I’m at it, let me have control of Consumer Goods back, too. If I choose to favour something else instead – like bullets, bandages, and beans – then I’ll take the hit to National Unity/morale. And what’s up with that ‘8-per-trade’ rule for all Resources? What’s that, Joe? Different article? OK.

5) A look at the Supply Use of air/naval units would be nice as well. Again, I have not tested HoI IV enough to be vehement about this – and I am not a math whiz or an expert on military logistics and supply – but 100 submarines using only 1 Supply Point per day? If #2&3 were implemented perhaps this could be left alone, yet it doesn’t seem totally unbalancing anyway.

6) Finally – although I am confident it will be addressed in future patches, since it has been included in discussions of general AI issues and as an intrinsic part of naval invasions – the AI still has more to learn about how to use the system as is. Thanks for another soon-to-be-great game, Paradox!



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