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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 units for that landmass region will draw supply from. For overseas regions these are ports assigned by the AI. On the supply map these depots show as three gold crates. In supply map mode each province will show which stockpile they are supplied from; e.g., Rostock would show as being supplied from Berlin. This will also give you supply requested and received, plus the current amount of supply/fuel in the province.
The information for your nation's overall supply is shown by a tooltip at the top of the map. This tooltip is three small crates. It will be green for supply surplus and red for deficit. Cursor over it and you will receive all pertinent data for your national supply situation. When supply production is on in the production tab a tooltip on that slider will show how much supply you are producing. That value on the next day at 00:00 will deploy to all IC provinces meeting all the following conditions: 1) Is land connected to the capital, 2) Is Owned and Controlled, and 3) Is a Core province. The amount each IC receives is based upon supplies produced divided by the unmodified number of ICs receiving supplies. Please note overseas IC do not deploy supply, but they can be applied to the production of supply. While fuel is automatically converted its deployment follows the same rules as supply.
- 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 transferred 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. These supplies can be captured if the province is captured. After a short period of time (each night at 00:00), 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 principal 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.
- Every request to a province for supply includes a supply transfer cost that can be affected by revolt risk 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 requesting unit and its supply source will carry the request for supplies backward, aggregating other supply requests as appropriate.
- Supply moves one province per day. There are times when the supplies that units ultimately receive do not actually come from a stockpile. Ports receive fresh supply each day in most cases for a landmass, but this influx may stop if the port has achieved reserve levels (30-days FTM/15-TFH).
The supply map shows that the supply network changes constantly in response to unit needs. The supply network updates nightly at 00:00. 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. The following province color code describes the supply network:
- Green provinces are receiving all of their requested supplies, and local units will be fully supplied.
- Blue denotes a supply surplus, which builds up over time.
- Black shows provinces in a state of zero supply, but with the possibility of requesting relief.
- Brown shows a province has received supply, but not enough to meet demand.
- Red hatching denotes a limitation imposed by a lack of infrastructure in the province (i.e. supply demand exceeds the supply throughput). This is known as a "supply bottleneck."
- Red shows when a province with units has zero supply.
- Yellow denotes supply received does not meet demand and the infrastructure is damaged.
- The colors used on the map only refer to supply, and not fuel - although the mouse tooltip for each province will show specific numbers for both supply and 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.
There are three ways a player can manipulate the supply network:
- Transport planes: Transport planes are expensive, carry limited supplies, and generally require air superiority, but 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 until 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 determined by the demand of the stockpile province on any given day multiplied by the number of days for supply/fuel reserves (as of TFH, 15-days).
- 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 Vladivostok: 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.
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). The exception to this is the capital depot and its adjacent provinces. These have unlimited throughput.
- 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 FTM/6-TFH) 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 land (AKA Owned and controlled) has a bonus applied to the same occupied throughput causing it to have better values 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 .01 per level.
- Supply Organization research increases supply throughput .05 per level.
- Assigning a minister with the Logistics Specialist Trait as Chief of Staff (+10% throughput).
- 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 decrease revoltrisk activity and improve supply throughput in occupied territory.
- Building new infrastructure.
Effect of Infrastructure
The exact workings of the supply system are not fully known, but with TFH we are given better tools to understand it. With TFH you can open the console (the tilde key on many computers) and simply type "tdbg". This is short for tooltipdebug. Then the supply map mode gives you the infrastructure level and max throughput of the provinces. Maximum throughput can also be determined from the following formula:
4 * (1 + modifiers) * OAC * infra²
- infra is a number between 1 and 10.
- 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.
It should be noted that infrastructure below a base level of two has no throughput, but if any infra starting from a 2+ base is damaged (such as by bombing) and goes below two it will still throughput supplies.
We don't know exactly how the supply system determines what supply paths to create, nor do we know how it prioritizes them, but we do know how they have to function. For illustrative purposes infrastructure can be viewed as a multilane highway that only allows a fixed number of cars through per day. So, if you have a province with 10-lanes of infra with a throughput of 800-cars, feeding three other 10-lane provinces with the same throughput, the maximum combined cars those three provinces will receive is 800/day (even though they are capable of passing 2400-cars). If at any time the three provinces demand more cars than the first province can provide, that province will raise a red flag in the form of red hatchmarks and the supply system begins to break down. This is the "supply bottleneck" that leaves many armies starving on the Steppes of Russia. If you view infra and supply flow from this perspective, and use the new tools given, understanding and avoiding supply issues will be easier.
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). Since Semper Fi it has been possible to alleviate this problem and manually route supplies via the sea. The supply depot will still be overland, but the extra ported supplies can hopefully intersect your units. This is an issue for the logistics strategy portion of the wiki.
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.
- 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.
The supply engine calculates a supply destination for an SRing unit as if it was still at its original province for the entire time that the unit is SRing. The logistics AI ignores the unit while it is SRing and then "notices" it again once it stops SRing. But supplies that were already en route to its pre-SR location continue to move that way until they arrive at that location. When the SRing unit exits SR mode by arriving at its destination (or being manually stopped), the logistics AI notices it again and tries to send any needed fuel and supplies to its new location. But it does not recall the allotments that had been in transit to its previous location at the time the unit began its SR. Supplies are "fire and forget" from the AI's point of view, meaning once dispatched they must travel to their appointed destination before they can be reassessed as no longer needed at that location and possibly recalled back to the stockpile.
For instance, if a unit was 60 provinces away from its capital (e.g. Berlin) It take 1 day per province for the supplies to move, so it takes 60 days for the supply to reach where the unit was. Now you SR that unit to France. That is another 40 or so provinces from Berlin. The original supply now takes 60 days to go back to Berlin and more supplies are needed to go to where the unit is now at and that takes 40 days.
One way to partially get around this is to SR to the capital/supply depot on that continent first, then walk the division to its destination without SR from there on. It's slower, but it cuts down a ton on weird fluctuations in supply draw because the division reappears to the supply AI right on the stockpile, requiring no time or supply tax.
Moving Ships and Planes
You can literally move a TAC from Stalingrad to Paris in a few hours, but the supply system doesn't notice that this happened until the wing shows up at the destination. This means that ships and wings have a "spin-up" time if no ships or wings were based in the destination province. For instance you might occupy France and rebase 30 u-boats to French ports, only to wait a week before the fuel and supplies catch up to them at their new naval bases.
Lack of Supplies
Every unit attempts to have a 30/15(FTM/TFH) days reserve of supplies and fuel during wartime in the province where it takes supplies. For ground units, this is the province where it is currently located. For naval and air it is the province where they are based. If there are not enough supplies available in the province the units draws supplies from you will notice the poor-supply-icon warning you that the province's required available supply is not equal to or more than the units daily consumption. Penalties only start to occur when the unit no longer has a full days supply to consume each day at 00:00.
If the 30/15-day-reserve is completely exhausted, a unit will no longer be able to initiate a new move order to hostile territories or attack. The penalties then are:
- -50% combat modifier
- Can not move on offense or initiate a new attack
- You do not get reinforcements, organization or upgrades
- Out of fuel = -90% movement speed for units using fuel
Units out of supply will not reinforce, regain organization or upgrade, hence attrition will occur resulting in a strength loss. Through logistical bombing and/or port strikes, this can be used to wear down the strength and organization of units in any fortified position by denying them supplies and fuel, and thus enable an assault otherwise impossible. 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 and units consume no fuel ( and are also unaffected by lack of fuel movement penalty ).
Research, Leaders and Ministers that effect supply use
- 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
- Army Group leader reduces supply/fuel consumption 5%/skill level for units under his command
- Logistics Wizard reduces supply/fuel consumption 25% for his unit ( halved for each level of command between leader and units for HQ leaders ).
- Chief of Staff minister with Logistics Specialist Trait gives +10% throughput
- Chief of the Army with Bread & Butter Doctrine gives -10% supply consumption
- Chief of the Navy with Base Control Doctrine gives +10% Naval Base efficiency
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, stored in the provinces they are located in (land units) or based in (naval/air units). As the units advance they try to bring with them a full 30FTM/15TFH days worth of supply which moves with them. Thus units can start a campaign with 30FTM/15TFH days of supplies and march through poorly supplied areas until that reserve runs out. The supplies are only moved to the new province once a unit has fully completed it's move, so if an enemy units reach the province before all units have retreated out of it, they can capture part of the supply stockpile stored in the province.
- 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 its 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.
See also Logistics strategy 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