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There are three ways to move troops across water in HOI4:
Convoys (simplest and easiest method)
Naval Invasions (most costly but most reliable)
Paratroopers (situational)
Method 1: Convoys
The simplest, cheapest, and easiest way is to have your units board convoys.
This can be done by assigning them across a body of water or by stationing them in a port, then right clicking to move them to a friendly port across the water.
The troops will automatically cross the ocean to their new orders.
There’s a few things to keep in mind when doing this:
Each division requires convoys. Heavier units (larger divisions) require more.
Your divisions are open to enemy attack and can be lost to the enemy at sea.
They will only cross the water this way if there is a port on the coast and at the destination. Otherwise, they will stand still with a yellow exclamation point.
This is also the most vulnerable method and is not advisable during wartime. Be sure to escort units in transit with your navy and airforce.
Method 2: Naval Invasions
Naval invasions are the most common way to move your troops across water to enemy territory.
However, they also take the longest and can be the most costly in terms of manpower and industry.
For example, if you invade from Iwo Jima to Tokyo you would need naval supremacy in both the Mariana region and the coast of Japan.
I would need naval supremacy in both the Tyrrhenian sea and the western Mediterranean.
Every naval zone you go through requires you to have 50% or more naval supremacy in each of them. If you don’t know what zones you need supremacy in, hover your cursor over the arrow button above the army.
Any unit can take part in a naval invasion, even super heavy tanks or anti-aircraft guns.
Marines have a huge 50% attack bonus when attacking through a naval invasion, making them ideal for the task. Employ as many of them as you can in your naval incursions.
To begin a naval invasion, select the units you want to use. At the start of the game you are limited to 10 divisions per invasion.
Next, select the naval invasion icon (it looks like an anchor with an arrow).
This will highlight all ports in blue. Click on the port you wish to use as the source.
It is right next to the Naval Invasion with Floating Harbor and the Paradrop orders.
Next, right click on the coastal provinces you want to land in. You can select as many as you want in the vicinity of the first one you select. This will tell your troops to land in all of these at the same time.
Tip: I recommend spreading your invasion out around a port tile. The AI almost always garrisons ports but not the empty tiles around them.
The Norwegian army is likely garrisoning Kristiansand and Stavanger but not the two tiles in between.
Once the invasion begins use the units that have landed to surround the ports and apply pressure to help take the ports.
The main drawback to naval invasions is their speed. Without any technology a full invasion force will take 70 days to prepare.
A couple points to remember about naval invasions:
Each division you assign requires convoys. The invasion won’t start until they have all required convoys.
The AI loves to do naval invasions behind your lines, especially the British and Japanese AI. You can prevent this by maintaining a garrison or naval supremacy on your coastline.
Invasion capacity can be increased by the relevant technologies under the naval tree tab.
Preparation time can be drastically reduced by technologies and by having multiple orders under the same army.
To resupply your troops you need to capture a tile with a port (they look like little anchors on the map).
Method 3: Paratroopers
Paratroopers are a bit more situational than the other methods here, but are the fastest because they require no preparation time.
Paratroopers require you to research the paratrooper technology (it’s near the bottom of the infantry tech tree, the symbol is a parachute.)
The divisions themselves are nothing special as they have similar stats to base infantry. What makes them useful, as the name implies, is their ability to be paradropped.
They also require available transport planes. These are available at the start of the game to most countries so it’s just a matter of producing them.
Unlike naval invasions, you cannot select multiple tiles to automatically have your troops spread out in. You can get around this by assigning multiple orders.
To assign a paratrooper to a paradrop, first move transport planes to the airfield closest to the landing site.
Then select your paratrooper divisions and click the parachute icon at the bottom of the screen. Clicking that will highlight all airports on the map in yellow, and the ones with transport planes in blue.
Next, click on the blue airport, then on where you want your men to be dropped into.
You’ll also need at least 50% air superiority in every airzone you pass over.
Unlike naval invasions, paradrops require no preparation time. This makes them ideal for quickly taking small islands and underdefended territory.
And here’s some extra information to know when using paratroopers:
There really is no “best” paratrooper template. I like to use smaller templates since each one will use less special forces, which in turn gives me more divisions.
Paratroopers tend to lose lots of equipment so there’s no need to give them motorized recon or anything.
It should also be noted that the AI will make paratrooper divisions, but will not use them as paratroopers. Instead, it will employ them as infantry.
Expect to lose some in contested drops. You can move your navy manually to the coast of that province to find out if it is garrisoned.
Their range is limited by the transport aircraft.
Paratroopers are not well suited to be at the frontline. Use them to capture under defended territory then move your mainline infantry in.
You cannot add any non-paradroppable units to a paratrooper template. You can check if something airdroppable by checking to see if it has a little green parachute in the designer.
Paratroopers count as special forces so they are limited based on the size of your army.
