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This article describes the logistics system in HoI3, focusing on the mechanics of supply depots, the supply network, and supply throughput. For strategic advice on logistics, visit the Logistics strategy article. Note that the Semper Fi expansion adds a new, optional game mode called "Arcade" where the entire supply system is circumvented. In this game mode, supplies are simply drawn directly from a national stockpile.
Supply depots (aka "supply sources" or "supply centers"), are a physical location on the map where all excess supply in a landmass region will try to travel to each day, 1 province per day. They appear as three gold crates in a province. The national supply tooltip information is a direct extraction of all the values of the capital province in supply map mode. If supply production is currently on in the production tab then a tooltip on that slider will show how much supply units will be produced for the next day. That value on the next day at 000 will deploy amongst all IC provinces meeting all the following conditions: 1) Has a land connection to the capital, 2) Is Owned and Controlled, and 3) Is a Core province. The amount each IC receives is based upon the amount of supplies produced divided by the unmodified number of ICs receiving the supplies. Please note that overseas IC do not deploy supply, but they can be applied to the production of supply. These rules also apply to fuel production and deployment.
- The overseas supply source for any territory not connected to a nation's main land is a port.
- The tooltips for the national stockpile on the top of the screen are:
- Into network= The amount of supply deployed to qualified IC. This number is derived from the supply produced minus any supply deployed to the capital IC.
- Convoyed out= How much supply is being sent out in convoys each day(supply does not travel from the capital to a port to ship out through a convoy, supply will magically just ship out with no effect on the supply map mode.
- Returned to stockpile= Excess supply that is transferred into the capital province that day from adjacent provinces or a convoy from a landmass that is empty of units but has supply present in it.
- Traded away= supplies you are selling to a nation or supplies distributed to an ally to cover costs of your units operating in their supply networks
- Traded for= Supply coming in from nations you bought supply from.
- Used= The amount of supply transfered from the national stockpile into the capital province to meet the demands of all land-connected units. This includes aircraft and ships drawing supply from their respective non-overseas bases/ports.
- Produced= the value from the previous day in the production slider tooltip for supply production.
Apart from supply sources, any province that has received more supplies than the units in that province used will temporarily store these supplies. Thus, these supplies can be captured if the province is captured. After a short period of time (each night at 000), any provinces with surplus supplies (other than a supply depot) will send them back to a supply depot along the supply network. There is no throughput cap on supplies heading back to the center, and no supply tax.
The game has one principle supply network method used for transporting supplies on land and overseas:
- All units draw supply by requesting it from the province they are located in.
- Each province starting from the unit's location leading back to the supply stockpile it is listed as being "supplied from" will request supplies from the province next in line and never cross itself.
- If the next province in line doesn't have any supply in it to transfer (and no units in it)the province will show as black. If it has supply but not enough to meet the needs it will be brown. Green with red hatchmarks is supply throughput maxed provinces is land that is at its max throughput.
- Every request to a province for supply includes a supply transfer cost that can be effected by revoltrisk if the land is occupied/annexed.
- If one adjacent province cannot meet the total supply need, multiple adjacent provinces may be used but never beyond a 90 degree arc in the direction of a stockpile.
- Each province between the requestor and a supply source will carry the request for supplies forward, aggregating other supply requests as appropriate.
- Supply moves one province per day. There are times when the supply units are recieving never came from a stockpile. Ports recieve fresh supply each day in most cases for a landmass, but this supply transfer can stop if the port has achieved reserve levels (30-days FTM/15-TFH).
There are three ways for a player to manually manipulate the supply network:
- Transport planes: While transport planes are very expensive, carry limited supplies, and generally require air superiority, they can surgically augment areas with supply problems.
- Supply missions can be used to siphon supply out of a large stockpile towards the front faster and more efficiently than land in low infrastructure regions.
- Convoys: AI control of convoy creation and destruction can be turned off, allowing a player to manually create convoys.
- If a landmass stockpile is beyond a certain value convoys will stop shipping supply till the stockpile drops down to a level where it needs supply again. This applies only to the stockpile port. Any other convoys you set up to the same landmass will continue shipping as long as they have a demand. This can cause you to overstock the landmass and waste supplies.
- Stockpile thresholds are a calculated equation based on the demand of the stockpile province on any given day multiplied by a certain amount of days, generally any stockpile over 40k stockpiled will not allow for convoys to ship supply till it drops below that. This value could be higher if the landmass has a great many units on it.
- Supply re-route: Starting in Semper Fi, it is possible to create sea convoys to improve the supply flow to areas already connected via land to the supply depot (Lenningrad and Vladivostock: in addition to a land connection, can also have a sea connection). This can happen so long as the provinces involved are separated by at least 10 provinces.
The supply map effectively shows the supply network is not a static network, but instead a constantly changing network based on unit needs. Thus, this map mode is a snap shot in time, not a comprehensive view of what your supply network might be capable of in different circumstances.
- Green shows it is receiving all of its requested supplies and every unit is in supply.
- Blue shows a supply surplus.
- Black shows zero supply, but can have requests.
- Brown shows province has received supply, but not enough to meet requests.
- Red hatching shows limitation being imposed BY the infrastructure (demand exceeds the throughput of the infrastructure).
- Red shows when a province with units has 0-supply.
- Yellow shows supply received does not meet demand and the infrastructure is damaged.
- There is no color for fuel.
For more details, view this post by potski on the HOI3 forums explaining the supply map and many intricacies and implications of supply draw.
Allies & Puppets
When units are in an allied nation, supplies will be drawn from the allied supply network. Meanwhile, an automatic and invisible trade route will be created between the two nations, where the exact amount of supplies and fuel will be sent from the nation with its troops abroad to the allied nation hosting those troops. Some minor allies and most puppets will relinquish control of supply in the region to their master nation or a major nation with better doctrine/techs for supply. Example: Manchukuo will never retain a stockpile in its capital and will always be supplied from japan's port stockpile in asia. They will constantly produce double daily supply because their supply system is basing its values off an empty capital province.
There are several factors that limit the distribution of supplies:
- Infrastructure: The supply throughput a province can funnel depends on its infrastructure (see below for details).
- Supply Tax: Moving supplies costs a base tax of 0.1 supplies (decreased by Supply Transportation techs) per province moved through.
- Port Size: For overseas supply sources, the size of the port (each level equals 4 supplies) limits the amount of supplies that can be convoyed.
- Revolt Risk: Revoltrisk multiplies the supply tax causing less supply in a province to be for units ahead in the line causing reduced supply throughput indirectly.
- Occupation vs Annexed Occupied land has the lowest throughput, Annexed AKA Owned and controlled, has a bonus applied to the same occupied throughput causing it to have better balues and core owned territory has no penalty for throughput. If you are unsure what a province is, when selecting the province if it has your flag on it with no circular emblem on it then it is owned and controlled, if it has an enemy flag and your emblem is on top of that flag then you are occupying. Core territory will have your emblem in the bottom left stating you have core on the land, its also represented in revoltrisk mapmode as having 0 local revoltrisk.
Supply Throughput can be improved through the following methods:
- Supply Transportation research reduces the supply tax per province.
- Laws can also affect supply throughput. Mixed Industry gives 5% bonus to throughput while Heavy Industry gives a 10% bonus to throughput.
- Less draconian occupation policies will decrease revoltrisk activity and improve supply throughput in occupied territory.
- The Army Group HQ will improve logistics by 5% based on each skill level of its commander.
- Building new infrastructure will increase the throughput of that province.
- Building IC in a core province without IC will create a new supply source and possibly improve nearby supply distribution. Never deploy IC to provinces outside of core/capital landmass locations.
Effect of Infrastructure
The exact workings of the supply system are not fully known. Maximum throughput has been determined to be:
4 * (1 + modifiers) * OAC * infra²
- infra is a number between 1 and 10. The infrastructure percentage gets divided by 10 and rounded down to a whole number. So a province with 29.9% infrastructure and one with 20% both have an infra of 2.
- OAC is 2 if the province is Owned And Controlled by the same nation, otherwise 1.
- modifiers are given by ministers, technology and strategic effects.
This was tested in a "linear" situation, that is a non-branching path of provinces. Maybe this limit is averaged over 2 days. It is unknown what happens when paths branch and merge.
Due to the quadratic dependence, it is more efficient to build up a single supply path to level 10 infrastructure than to have several paths at lower level, though there is also the strategic weakness of being vulnerable with only one supply path.
Ports and Supply Convoys
Wherever possible, a supply route will be created over land instead of a sea route. This is true even when the land route may be much longer than a sea route (e.g. when wrapping around the Mediterranean Sea, for example). In Semper Fi, it is possible to avoid this problem and manually route supplies via the sea.
Ports: Overseas supply functions with an origin port and a receiving port. There is no such thing as a more efficient origin port. A level one naval base with level two infrastructure will perform just as well if the numbers were level 10-each. There are no transfer costs or throughput limitations between the capital stockpile and the origin port. This is because the supplies do not move overland; they show up, through the convoys, directly at the receiving ports. While an origin port can theoretically send an unlimited number of convoys, a receiving port overseas can only receive one supply convoy and send out one resource convoy. Manually trying to game the system and make two supply convoys by ticking the appropriate boxes does not work. The supplies an overseas port can receive is limited by port level, with 4 supplies (FTM) per day per port level (6-supplies per day per level in TFH). A level 10 port can thus receive no more than 40/60 supplies per day which can, for example, support about 15 infantry divisions with artillery. These numbers are subject to improvement by the naval basing tech (+20% each level) and ministers. Therefore, large overseas forces require more ports in areas linked to your port ( = more possible supply convoys) or supply them by air.
Supply Convoys: Supply convoys use a number of transports equal to the length of the route (measured in terms of sea provinces) in order to operate at maximum capacity for the receiving port (determined by port level, as described above). Starting in Semper Fi, if units overseas need more supplies than the local supply depot can provide, additional supply convoys can be sent to other overseas ports. This will not create new supply depots overseas, but these will overcome the bottleneck introduced by the port size of the supply depot. Thus, all additional ports opened will funnel supplies to the local supply depot, which will then disperse supplies as needed.
Lack of Supplies
Every unit has a 30/15(FTM/TFH) days reserve of supplies and fuel during wartime. If there are not enough supplies available, it will begin consuming that reserve and you will notice the poor-supply-icon warning you that the province's required daily supply is not equal to or more than the units consumption. Penalties only start to occur when the unit no longer has a full days supply to consume each day at 000.
If the 30-day-reserve is completeley exhausted, a unit will no longer be able to move. The penalties then are:
- -50% combat modifier
- Can not move
- out of fuel = slower movement (only applies if you still have supplies)
- you do not get reinforcements or upgrades
Units out of supply will not reinforce, regain organization or upgrade, hence attrition will occur resulting in a strength loss. Combined with tactical bombing, this can reduce the strength of any fortified province to be enable an assault. Note that different units draw varying levels of supplies. Infantry will always draw less supplies than motorized divisions, for example. When strategically redeploying units, supply draw is doubled.
Research that effects supply
- Large Front: reduces supply consumption -0.01/level (HQs only)
- Guerrilla Warfare: reduces supply consumption -0.01/level (HQs only)
- Airborne Warfare Equipment: reduces supply consumption -0.1 (para, Gurkha & Ranger only)
- Supply Transportation: each level reduces transfer cost by .01
- Supply Organization: each level increases throughput by .05
- Port Efficiency: Base supply per port level is increased 20%/level
Due to issues some players have with constraints in the supply system, simple modifications can be made to the game's text file to change the way supply is handled. In the "Defines.Lua" file in the Common folder, the following variables are key:
- SUPPLY_TAX = 0.1 [the additional cost per "node"]
- MUDDYNESSSUPPLYTAXMODIFIER = 0.25 [additive to Supply tax for provinces in muddy conditions]
- OWNED_AND_CONTROLLED_THROUGHPUT_CAP_BONUS = 2 [Annexed land throughput bonus]
- INFRA_THROUGHPUT_IMPACT = 4, [base number of supplies that can be moved per infrastructure level]
- SUPPLYPOOL_DAYS = 30 in FTM, 15 in TFH [Number of days a unit has local supply stocks without needing the supply system]
The simplest method of improving the games difficulty level for a novice player is to simply play in arcade mode. Theres no need to modify files this way and supply is much simpler for both the player and the AI.
- A supply network cannot draw supplies from another supply network. It can only draw supplies from a naval base which is supplied by convoy from the capital. Ports do not have to be in supply to provide supplies to a convoy but they do have to be connected via land to the capital.
- Units carry supplies with them. As the units advance the local supply reserve also advances. Thus units can start a campaign with 30FTM/15TFH days of supplies and march through poorly supplied areas until that reserve runs out.
- HQs consume supplies. Higher HQs could remain further away, and still be in range of the Divisions. As the front advances, then this is less likely, and you need to make a decision between the combat and other advantages provided by the HQs, and the limited supplies. Adding Corps to the hierarchy (which is generally seen as a "good thing") actually adds to your overall supply consumption in an offensive. In some countries, the supply usage of a large force, say an Army Group, may be increased by 10-20% by all of the HQs. It is probably not a good idea for some countries to create Corps HQs as they need to remain close to the front and consume supplies that might otherwise go to the combat Divisions.
- Supply/resources can only travel once across water, not counting straits. Supply will sadly only trace from the depot. Putting more supply in other ports will help supplying those port provinces but little else. It will flood backwards into the system when units move through though. Every non-contiguous to your capital area is consider "overseas" and will have it's own depot. This can be as small as a single hex island or as large an area as several land connected continents. The larger the area overseas, the more difficult it is to supply. An overseas supply depot is treated by the AI just like your capital meaning that all supply to the overseas area will try to flow from the depot to where it is needed.
- Supply received via trade is handled exactly like mineral resources. It is delivered directly to your capital, magically skipping across provinces. This happens each day BEFORE supply need is calculated. It is then distributed back into your supply network. Computer programming here, nothing happens simultaneously.
- If for some reason an IC-province becomes isolated it will stop deploying supply. If your capital becomes isolated no supply will deploy to any of your IC. For all intents and purposes your capital is treated as an island surrounded by an infinite sea. You can still use your IC to produce supply, but all supply will deploy to the capital. Capitals with ports would be able to create supply convoys, but if you are at this point you have probably lost.
- Another thing that WILL screw up your supply is SRing a bunch of units. While your units may hop a train and move at warp speed to their destination, their supply won't. If you Sr a bunch of units into a region, it will take some time for supply to catch up. You should never ever strat-redeploy in areas where you have low supply and have divisions fighting. The redeploying units will carry off up to double their own supply reserve when they move (even if it means leaving the province dry for other units). They will take any supply along the way to maintain this double reserve, thus cutting your supply lines to ribbons. Fuel using units have their fuel consumption set to zero, thus they leave their fuel behind and arrive at their destination with no fuel.
- You can use transport aircraft to dump supplies as close as they can get along a supply route and they'll still be useful. They don't have to be dropped on the troops or an airfield or port for them to get in to the supply system. Anywhere on the route will do. Base them somewhere they have access to a decent amount of supply (supply depot if possible) and select the hex where you want supplies delivered. Watch them, though, as the AI will intercept them if it can.
For more information about the supply system see the Supply Guide. Also, read this thread: http://forum.paradoxplaza.com/forum/showthread.php?697889-Manual-Supply-routes