Hearts of Iron 4, Paradox’s gloriously complex WW2 sandbox, has (like most Paradox games) a notoriously steep learning curve. Of all the tricky and fiddly strategic maneuvers that you’ll need to execute in order to emerge victoriously, naval invasions are the most difficult.
This guide will tell you how to channel your inner-Eisenhower and launch an amphibious invasion that will succeed, whether you’re the Allies preparing to liberate France via Operation Overlord, or the German Reich trying to make Operation Sea Lion a reality and bring down the British Empire.
How to Prepare for a Naval Invasion in HOI4
Like the real-life D-Day landings, it isn’t possible to just launch a naval invasion on the spur of the moment—planning and preparation are needed.
Before your divisions can even think about boarding the boats, there are certain conditions that need to be met.
Condition 1: Owning a Province With a Naval Base
This is simple really—if you’ve got nowhere to launch the invasion from, it can’t go ahead. Make sure you own at least one naval base, preferably close to the location you intend to invade.
The bigger the naval base, the more efficiently your invasion will be able to proceed. Of course, if you own more than one naval base then you can launch multiple invasions, increasing your chances of success.
Condition 2: Enough Naval Invasion Capacity
This one can be a killer. You’re all set, ready to execute your strategic masterplan and launch your war-winning HOI4 naval invasion… and then you realize that you can only invade with a paltry 10 divisions.
Why? Because you haven’t researched the right technologies and you don’t have enough capacity.
The “transports” branch of the “naval technologies” tree determines how many divisions you can use in a naval invasion. The base value is 0, going up to 10, then 40, and finally 100 divisions once you’ve researched the most advanced technology.
If you’re planning something big, make sure you’ve got the tech to do it.
Condition 3: Naval Supremacy
For your invasion force to pass through a sea zone, you need to have at least 51% naval supremacy in that zone. To achieve this, you’ll need to assign your ships and navies to patrol or intercept in that zone. Using your air-force to accomplish air-superiority will also help.
It’s worth noting that you need supremacy in every sea zone your fleet is going to pass through, not just the one nearest to the province you’re invading.
The further your HOI4 naval invasion has to travel, the more fleets and planes you’ll need.
Condition 4: Convoys
The actual transportation of your precious troops is done by convoys, so make sure you have enough. Different types of divisions have different “weights” that determine how many convoys you’ll need.
As a rule of thumb, try to have at least 1.5 convoys for each division taking part in the invasion.
Handy HOI4 Naval Invasion Hints
You’re almost set! But before you set off, you might want to consider these handy HOI4 naval invasion hints.
Naval Invasion Hint 1: Destroy or Dodge Enemy Fleets
A major threat to your naval invasion is from interception by enemy fleets. Not only can this cause your invasion to fail, but you could also see your divisions taking a scenic detour—to the bottom of the deep blue sea.
You should always try to destroy any enemy fleets in the area, either with your own navies or using naval bombers.
If this isn’t possible, you can try to ‘sneak’ your invasion across when the enemy fleet is out of the area, but this is risky—you might want to save-scum on this one.
Naval Invasion Hint 2: Use Marines
Normal infantry, mechanized, or tank units suffer some pretty heavy negative modifiers when attacking as part of a naval invasion, so you might find your crack panzer divisions being held off by the HOI4 equivalent of Dad’s Army.
To get around this, use marines to make the initial assault. Marines actually get bonuses when attacking as part of a HOI4 naval invasion, so they are more likely to succeed.
Remember too that you can research upgrades to your marines, making storming the enemy beaches even easier.
Naval Invasion Hint 3: Target an Enemy Naval Base
Although you can, in theory, launch a naval invasion of any enemy province with a coastline, you should always target an enemy naval base.
Without one, your invading army will be out of supply, and will most likely be surrounded and destroyed.
How to Launch a Naval Invasion in HOI4
Okay, almost there. It’s now time to actually launch your naval invasion in HOI4. Here’s what to do:
- Select the army you want to carry out the invasion. Make sure that all the divisions taking part are in the province containing your naval base.
- With the army selected, click on the naval invasion icon.
- Left-click the port you want to invade from, then right-click on the province you want to invade. This will start the planning phase of your invasion—the invasion will take some time before it’s ready to be launched. This will depend on a number of factors, including the number of divisions, the size of your naval base, and tech levels.
- Once the planning phase has finished, click again to activate your army—your invasion is finally underway!
Launching a Successful Naval Invasion in Hearts of Iron 4
Naval invasions in HOI4 are complex and difficult to do right but, when they succeed, it always feels worthwhile. They can deliver a decisive, war-winning blow, catch your enemy by surprise, and help you to feel like a bad-ass conqueror (or a righteous liberator).
The only thing we have left to say is good luck and bon voyage—and let’s hope you don’t get sea-sick easily. For an even more detailed look at naval invasions, check out the Paradox wiki.