Hearts of Iron 4 (HOI4) – How to Increase Supply

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In Hearts of Iron 4, your biggest enemy will more often than not be Supply. As soon as you see that annoying red supply bag above your troops, you will start seeing real hits to your equipment and Manpower pool.

To stop this useless loss of resources, you will need to somehow increase the Supply in those provinces.

Recommended Read: Best Air Doctrine in HOI4

Most players don’t really understand how Supply works, which is why they often fail to provide enough of it for their dying troops.

There are a few ways to increase Supply in Hearts of Iron 4, and those are to increase Motorization levels, build new Supply Hubs, build Railways connecting Hubs, and to improve Infrastructure.

Table of Contents

How Supply Works

Supplies aren’t physical items you build. Instead, they’re a resource automatically generated in your states based on factors like population, infrastructure, victory points, and how well-connected they are.

Each division has a “supply appetite.” They need a certain amount of supply to function effectively. If they don’t get enough, their organization suffers, making them easier to defeat.

There are two ways your troops get their supplies:

  • State Supply – This comes directly from the province itself based on population, infrastructure, and victory points. Think of it as the local food stores and farms keeping your troops fed.
  • Hub Supply – This comes from a network of supply hubs connected to your capital. Think of these hubs as regional distribution centers sending supplies to your troops on the front lines.

Your capital acts as the main supply hub, sending supplies to other hubs via railways. The maximum amount of supply your capital hub can handle depends on the number of factories you have. It’s like a giant warehouse with limited space.

This capital supply cap doesn’t directly dictate how much reaches all your hubs. It’s just a total limit. Each individual hub also has its own maximum supply level based on the quality of the railway connecting it to the capital.

Beginner Explanation

So, imagine your capital as a giant supply depot. It has a limited capacity, the Supply Cap, based on your factories. This cap represents the total amount of supplies it can hold and distribute.

Now, you connect this central depot to other smaller depots called Supply Hubs using railways. These hubs act like regional distributors, sending supplies to your troops. Here’s the catch:

  • The maximum supply a Hub can provide depends on the railway quality connecting it to the capital. Better railways mean higher supply flow!
  • This Hub’s supply capacity is either based on the capital’s Supply Cap or the railway level, whichever is lower. Think of it as a bottleneck.
  • The Hub then distributes supplies to nearby troops. If the total amount of supplies needed by these troops is greater than the Hub’s cap, they won’t get enough.

Railways only connect hubs to the capital, they don’t directly supply troops. Building a railway to a province with no supply won’t magically create some!

By keeping your capital’s Supply Cap high (more factories) and upgrading railways, you ensure your troops get the supplies they need to win!

How to Increase Supply in HOI4

There are four ways to increase Supply in a state or province in HOI4:

  • Increase Motorization Level
  • Increase Railway Level
  • Build Supply Hubs
  • Increase Infrastructure Level

Increase Motorization Levels

Every Supply Hub in HOI4 has a limited range for supplying troops. This range depends on your chosen Motorization Level, which essentially determines whether you use trucks or horses for deliveries.

Motorization Levels:

  • Horse (Default): This is the standard option at game start for both Hubs and armies. It has a short range but requires minimal resources. Great for early game when trucks might be scarce.
  • Trucks: Upgrading to trucks increases the Hub’s supply reach and the amount of supplies it can deliver to existing provinces. However, you’ll need to dedicate trucks in your Logistics to keep this supply flowing.
  • Many Trucks: This doubles the range and supply of the “Trucks” level, but also uses twice the amount of trucks.

There are two ways to leverage Motorization Levels for better supply:

  • Individual Hub Control: Click on a Supply Hub in the Supply Map Mode. You’ll see three bubbles on the right. The rightmost one represents Motorization Level. Click it to switch between Horse, Trucks, and Many Trucks.
  • Army-Wide Priority: Set a global preference for all your armies. Select an army or army group, then click the “horse button” above its weight (the boat icon) to adjust the Motorization Priority. Be careful though, prioritizing trucks for all armies can strain your economy if you’re not prepared.

By choosing the right Motorization Level, you can ensure your troops receive the supplies they need, no matter where they are on the battlefield.

Increase Railway Levels

The maximum supply a Hub can provide (its cap) depends on the quality of the railways connecting it to your capital. This can become a problem if you have too many divisions stationed near a Hub, causing it to reach its capacity.

You can increase the supply capacity by improving the railways between the Hub and your capital. Here’s how to do it easily:

  1. Open the Supply Map Mode and click on the affected Supply Hub.
  2. Look for the button labeled “Upgrade Bottlenecks” in the middle.
  3. Clicking this button will automatically optimize the railways connecting the Hub to the capital. This can involve either:
    • Eliminating bottlenecks – Ensuring all railway segments between the Hub and capital are at the same level, removing any bottlenecks that restrict flow.
    • Upgrading the entire line – If all segments are already the same level, the button will upgrade them all to a higher level, increasing the overall supply capacity.

If you conquer a new Supply Hub and it lacks supply, the most likely culprit is a missing connection.

Simply build a railway from the Hub to any existing railway line in your territory. This will integrate the Hub into your supply network.

Build Supply Hubs

A common challenge you’ll face is the vast distance between existing Supply Hubs. This creates gaps in your supply coverage, leaving some areas underserved. To solve this, you will need to build new Supply Hubs.

However, constructing Hubs is a heavily time-consuming process. In the base game, it can take a significant amount of time to complete just one.

To counter this, consider prioritizing the construction of essential Supply Hubs at the beginning of the game. This proactive approach ensures your troops have the coverage they need from the outset.

Many countries have access to a national focus called “Reorganize the Railway System.” Completing this focus significantly speeds up the construction of Supply Hubs, allowing you to build them three times faster.

By strategically placing new Hubs and taking advantage of this decision, you can ensure your troops have a reliable supply chain, even in remote areas.

Increase Infrastructure Levels

Even with a well-developed network of Hubs and railways, sometimes you might need an extra supply nudge in specific regions. This is where Infrastructure comes in.

Building Infrastructure in states facing supply issues provides a small but helpful bonus. Each level of Infrastructure adds 0.3 Supply to all provinces within that state, reaching a maximum of 1.5 Supply at the highest level.

This bonus is fantastic because it’s “free” supply, not relying on Hubs or railways. It’s also used first, before supplies from Hubs, ensuring your troops get this local boost first.

Essentially, well-developed infrastructure acts as a local supply buffer, reducing the burden on your Hubs and ensuring your troops have a reliable baseline supply.

This can be particularly helpful in remote areas or during the early game when Hub construction might be limited.

That’s everything you need to know about how to increase Supply in Hearts of Iron 4!

Have any input or suggestions for this guide? Let us know in the comment section below.

Adrian Oprea

Based in London, United Kingdom, Adrian Oprea is a Guides Writer. As a professional single-player RPG player, Adrian has often been stigmatized. He has decided to pour his frustration into writing guides!

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