Hearts of Iron 4 (HOI4) – Japan Strategy Guide

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During World War 2, the world had to face the combined powers of Germany, Italy, and Japan, which ended in the loss of the Axis. However, in Hearts of Iron 4, players can take the mantle and guide the nation in the right way and change history forever.

Japan is one of the main antagonists of the war and the biggest problem for the Allies, considering they had to drop a few nuclear bombs to finish them off.

Recommended Read: Hearts of Iron 4 – France Guide

In Hearts of Iron 4, players can have many problems playing as Japan, since naval combat can be extremely confusing and island hopping is probably one of the most annoying mechanics in the game.

In this guide we will give you a general strategy to use for Japan in Hearts of Iron 4 to defeat the Allies and the USSR, and some pointers on how to use the navy to its full potential to dominate the Pacific.

Table of Contents

General Strategy for Japan in HOI4

Japan has one of the best starts in HOI4, so there really isn’t a lot to plan. For the war with China, the biggest problem will be the Marco Polo Incident national spirit that will give Japan huge debuffs.

At the start of the war you will have a -50% negative modifier for Attack against the Chinese warlords. To fix this, you will need to press the button to escalate the war every time it appears in the Decisions tab.

You can either just wait to completely remove the debuff or start pushing once it’s weaker. By doing enough Prepare Collaboration Government operations, you should have an easy time capitulating China without even reaching Chongqing.

Once the war with China is done, you will move most of your troops to Europe and prepare to defeat France and the UK. Both of them should be defeated using naval invasions.

The USA and the USSR won’t really be a problem for you since you should have defeated the main powers that could oppose you by 1941.

How to Start as Japan in HOI4

Your first moves as Japan will be fixing some of the templates, setting up a better Civilian economy, and preparing for war by getting a lot of Army Experience from the conflicts before the Marco Polo Incident.

When it comes to focuses, Japan doesn’t really suffer from any annoying negative modifiers, so we’re just going to rush the Spiritual Mobilization focus just to make our army even better and then immediately go for the Marco Polo Incident.

For the Interservice Rivalry, we’ll heavily favor the Imperial Army, since they just offer better bonuses overall and your Navy is strong enough to take care of most problems in its current state in singleplayer.

If you are in a multiplayer session, then you might consider staying in the Balanced situation.

Most of the early game will be preparation for the Sino-Japanese War. Generally, the war shouldn’t take more than a year if you play your cards right.

Germany shouldn’t even have time to attack Poland by the time all of China is annexed by you.

National Focuses

All we need to do here is get the Spiritual Mobilization focus to get a huge boost to Manpower. After that, we will rush the Marco Polo Bridge Incident and you can do whatever you want after that.

Here are the focuses you will need to complete to win the game as Japan:

  1. Purge the Kodoha Faction
  2. Guide the Zaibatsus
  3. National Mobilization Law
  4. National Research Policy
  5. Nationalize War Industry
  6. National Defense State
  7. Spiritual Mobilization
  8. Liaison Conference
  9. Greater East-Asian Co-Prosperity Sphere
  10. Marco Polo Bridge Incident


Japan has the 4th largest military economy and the 6th largest civilian economy at the 1936 start in HOI4. This is a really good starting point and, after the conquest of China, you will likely be the world’s greatest power.


We’ll start off by increasing our Steel production and improving the Civilian Economy, since Japan is a bit underwhelming on that front.

Once we get a total of 30 Civs, we can start building only Military Factories everywhere.

So, here’s how your Construction menu should look at the start of the playthrough:

  • Tohoku +3 Infrastructure
  • Tohoku +4 Civilian Factories
  • Koshinetsu +3 Infrastructure
  • Koshinetsu +3 Civilian Factories

Later in the game, we will also need to upgrade the Railway system in China, since most of our units there will suffer from attrition otherwise.

Increase the Railway level to 3 from Dalian to Mukden, and from East Hebei to South Chahar.

An Air Base right next to Beijing will also help you a lot since you won’t need range on your planes and can combat the Chinese effectively.


As most countries in HOI4, Japan starts with a huge Infantry Equipment deficit. Since our main enemy will be China until around at least late 1940, we don’t really need to produce anything too complicated.

First, let’s boost the Infantry Equipment production by 2 factories, same with Support Equipment and Towed Artillery.

Then, remove the Light Tank production and the planes at the end of the line. Replace the two planes with the Ki-2, a better CAS than what Japan is producing right now, and B2M for the Carriers.

With the last remaining factories, start producing Trucks and Trains.

Here’s how you should set up the Production lines:

  • Infantry Equipment: 5 Military Factories
  • Support Equipment: 3 Military Factory
  • Towed Artillery: 3 Military Factory
  • Trains: 1 Military Factory
  • Truck: 1 Military Factory
  • CAS: 1 Military Factory
  • Carrier Naval Bomber: 1 Military Factory

For the navy, just fill up the production lines with Naval Dockyards to make sure that they fill up the next one in line once a ship finishes, and complete all of the subpar ships that Japan has already set up for production.

But, make sure to move the Heavy Ship, Carrier, and the Converted Cruiser at the end of the line.


Japan starts with a relatively large military, 60 divisions, over 200 ships, and around 700 planes.

First of all, get the only Marine division in its own army and set up Hitoshi Imamura, the Commando, in charge of it. This army will be very valuable for most of the playthrough.

Now, Japan starts with two Infantry templates: the Hohei Shidai and the Chuton-chi Shidai. The Hohei has 24 width, Engineers, and Recon. The Cuton-chi has 12 width and no support.

Set up an army out of all the Hohei divisions (15) and then take out 2 of them for a volunteer army that we’re going to send all the way to Ethiopia to grind some Army Experience.

Get 2 Hohei divisions and place them in another army with 2 Truck divisions. These will be sent to Spain once we raise our total division count.

You will also have 9 Cavalry and 3 Light Tank divisions. Change them all into the low priority Chuton-chi. Cavalry won’t be needed in China and the light tank division is a joke.

Now, for the air force, select all of your planes and disband them. They are very disorganized and positioned in bad locations. This is the easiest way to reorganize them and decide which ones are useful and which ones are not.

Before making new air wings, let’s get rid of the useless ones. Sell on the market all of the Ki-1, Ki-3, Aichi-D1A2, and A4N planes, since they’re all really bad or useless.

When it comes to the navy, just unite all the fleets into a super fleet and then split it into two. This will be more than enough for the Sino-Japanese War.

Intelligence Agency

The Intelligence Agency will be very important to quickly conquer China and start working on fighting the rest of the world.

The only upgrades you’ll really need are:

  • Army Department
  • Naval Department
  • Airforce Department
  • Pills
  • Localized training centers
  • Cryptology Department
  • Radio Interception Group x2

Build a network in China and complete the Collaboration Government operation as many times as possible to increase their surrender limit as much as possible.

Without completing the Prepare Collaboration Government operation, you will likely have to conquer almost all of Nationalist China to win the war.

Interservice Rivalry

Japan has an interesting mechanic where they can choose to prioritize either the Imperial Army or the Imperial Navy, at the detriment of the other. This means that you can get huge bonuses to one part of the army while making the other one weaker.

With each one of these decisions, the player can change the balance of power between them, giving bonuses to one and negative modifiers to the other. For example, doing a decision that strengthens the navy will have the following results:

  • -5% Factory Output
  • +5% Dockyard Output
  • -10% Military Factory Construction Speed
  • +10% Naval Dockyard Construction Speed

There are a total of 5 stages this rivalry can reach. At the start of the game, they are in total balance, which brings no modifiers. You can strengthen them two times, which would bring the following results:

Interservice Rivalry StatusOutputConstructionSpeedExtra Effects
Army Dominant-0,5-0,5Land Doctrine Cost -5%Naval Doctrine Cost +10%Naval Research Speed -10%
Army Strengthened-0,5-0,5
Navy Strengthened-1-1
Navy Dominant-0,5-1Naval Doctrine Cost -5%Planning Speed -10%Land Doctrine Cost +10%

Generally speaking, the bonuses on the Army Dominant/Strengthened side are much better than the ones for the Navy. For this reason, we will likely spend most of the game in the Army Strengthened status.

The choice to prioritize steel for guns is extremely good, since you can get 4 Military Factories almost for free while also giving the equipment production big bonuses. 

How to Win WW2

Volunteer Army

If you’ve read our previous guide on Germany, then you’d know this is the way to go as a Fascist country in HOI4.

First of all, we’ll send the 2-division army into Ethiopia and position them in the mountains in Gondar and the province to the east, south of Macalle.

We need to do this not only to annoy Italy, but to farm a lot of Army Experience by defending in the mountains forever while Italy defeats Ethiopia in the south.

When the Civil War starts in Spain, send the 4 division army with the Motorized units and as many planes as they allow you to send.

You do not care if Nationalist Spain wins or if Ethiopia survives, your main goal is to just stand there, get attacked constantly, and farm Army Experience.

Once you build up some Army Experience, it’s time to change the Hohei Shidai division. We’ll remove three Infantry battalions from the last column and add one single line Artillery. If you have enough Artillery, also add one as a support company.

China will only deploy Infantry units, so if you want to easily defeat them, just add any kind of armor into the template (Armored Recon or one Medium Tank).

The Sino-Japanese War

After you complete the Marco Polo Bridge Incident focus, you will gain a war goal on China. Instantly declare war. However, do not even consider pushing them at this time.

You will start the war with a giant -50% Attack, which we’ll first need to partially remove before conquering them.

Open the Decisions menu and press the button to escalate the war. This will remove some of the buffs from the Marco Polo Bridge Incident national spirit. Keep an eye out to press the button each time it is available.

Also, do not call Mengkukuo into the war. You can call Manchukuo, since they will give you an extra tile at the border with China to fight, allowing them to attack in more places.

Yes, you want China to attack you, not the other way around.

The strategy is to just patiently wait while China attacks you at the border. Due to the horrible debuffs you get, they will think they’re more powerful.

If they aren’t attacking, move some troops back using a fallback line to trick them into throwing themselves at you.

CAS will be really important here, since you can destroy their troops just by standing there, and they’ll have no defense for it.

Once you maybe press the escalate war button 2 or 3 times, launch a naval invasion into Shandong. Try to land in at least 3 provinces on the peninsula, since you will otherwise get encircled and you’ll lose all the Marines.

Do not deploy a lot of troops on this front. As long as your Marines have Artillery and maybe Armored Recon, just to cheese the whole thing, you can easily push to meet up with the army in the north.

The goal will be to do a huge encirclement where you eliminate most of the Chinese army. Remember that your only enemy in this war is Nationalist China.

You do not need to even attempt to capitulate Communist China, Shanxi, or any of the warlords. Ignore them and push into the leader of the faction.

Once you’ve united the naval invasion force with the northern army, continue the push and prepare a new naval invasion in the south. The best target would be Shanghai. This will allow you to quickly take over their capital and speed up their surrender.

We continue with the same strategy as before. Try to meet up with the northern army while encircling the troops next to the water.

After that, launch the final naval invasion even further south, into Fuzhou, and the whole oceanside of Nationalist China will be yours.

Now, if you manage to get to Changde with a Collaboration Government prepared, China should surrender, with your victory coming right at the beginning of 1939.

Either way, you should be done with the Chinese warlords by the time Germany starts attacking the Allies.

Since we’ve done Collaboration Governments, annexing all of China is usually the best idea. If you will haven’t, then puppet them and get all of their resources and demand war reparations.

World War 2

At this point, your only challenge will be the Allies: the United Kingdom and France. These are the only two countries you need to capitulate to become the world’s greatest power.

First of all, pump out at least 23 weak Infantry divisions to garrison your ports and Victory Points in mainland Japan. You do not want to randomly see the naval invasion notification and find yourself with Australian troops in Tokyo.

You’ll also need at least 22 divisions to protect the coastline of China and Korea. Again, you don’t want to have to bring troops back to Asia, so just leave decent garrisons in these ports and VPs.

Set up some frontlines with French Indochina and India and you should be ready for total war.

If Germany hasn’t started the 2nd World War yet, you can ask for docking rights there and military access in Italy to bring your army to Europe.

When you have your army ready in Europe, complete the Demand Indochina decision, which should trigger a war with the Allies. This decision is available by completing the Strike South Doctrine.

Once at war with France and the UK, Germany should finally give you military access, which should guarantee your win. Use your large navy, which should all be united into one large fleet, to gain naval supremacy in the Channel and set up a couple of naval invasions in the northern part of France.

Make sure to use Marines for this since they will have troops on the ports. Once you’ve managed to gain a foothold, bring all your troops from Germany and capture Paris, to capitulate France.

If France has already been defeated by Germany, then just bring your troops in France and prepare to do a Sea Lion. Conquering France would be preferable, but this works too.

Start a naval invasion from France into the UK, or drop some paratroopers on a port, and push into their country until they capitulate.

What to Do Next

At this point, you’ve finished almost all there is to do. You will have two enemies left: the USSR and the USA.

To defeat the USA, just conquer one or two provinces of Canada in the peace deal and you will have free reign to destroy them using your superior army.

For the Soviets, you can just fight in the east and push through Siberia to help Germany capitulate them.

Either way, this game of HOI4 is generally done by this point. If you really have high ambitions, you can also fight Germany and establish yourself as the greatest power in the world.

That’s everything you need to know about how to win WW2 as Japan 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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