How To Conduct Hearts Of Iron 4 Naval Warfare

Conducting effective naval warfare is vital in HOI4. Not only can you use your fleets to blockade an enemy’s supply lines they can also be used to perform naval invasions, sometimes saving you a lot of time fighting it out over a long land route. The Man the Guns DLC was not enabled for this game.

Naval invasions, raiding convoys, convoy protection and outright combat between fleets is how you conduct Naval Warfare in Hearts of Iron 4. Navies can be the key to preventing enemies slipping into your territory unexpectedly or losing valuable supplies due to convoy raids.

Hearts of Iron 4 Naval Invasions

Make things simple at first. Just like Armies fleets can be assigned theaters. Your theater will start out with something generic like German Theater 1. If you’re planning to invade the Netherlands for example, then rename or create a theater that gives you an idea of the location. For that reason, I renamed my first generic theater the Norwegian front since I planned on that country being my first victim.

Next, assign the fleets and task forces you want participating in that theater. Assigning them will not have any real impact in the game itself but it does make things easier to keep track of.

To start planning a naval invasion select an army or some divisions and click the naval invasion icon in the battle plan panel. There will some informational text in the top of the Battle Plan panel that tells you how many divisions are being assigned to the Naval Invasion. If it says, “0 divisions will be assigned,” or it shows a number that is less than the number of units you selected then the missing units may be trying to execute other orders they’ve already been given. You can cancel any previous orders by clicking the Unassign Divisions icon to cancel any orders they might be trying to carry out. All selected divisions should then start preparing for a naval invasion.

All available ports to start the invasion from will be highlighted on the map for you, just left click on one to select the one you want to assemble your invasion forces in. Once that’s done all target provinces will be highlighted, right click on one to select it. Right click multiple provinces in the same state to invade multiple territories, but all provinces must be in the same state.

Experience points for the Naval Doctrines are gained through Naval Exercises and some National Focuses, plus combat.

The play button needs to be clicked to activate this battle plan as well. The plan will not execute until war is declared and all the armies are in position.

You also need enough intel and convoys to support the invasion or it won’t be executed. Hovering over the play button will activate a tooltip giving you a lot of details about your planned invasion, including convoys. It will also give you details about how long the prep time will be, plus problems like not having enough intel to safely launch an invasion.

If you think you’re going to have a tough time invading an enemy province, or don’t have complete control of a sea zone you can assign a task force to naval invasion support. If the task force contains ships capable of bombarding the shoreline, they will do so to support your troops. A naval invasion is best conducted using Marines and not Army regulars.

If you don’t have enough intel on a region or sea zone the naval invasion will not be launched. Send some ships in to patrol it the sea zone or to raid convoys. Air patrols work too. The game will automatically select the zone the task force is already in, but you can right click to add more zones to patrol.

Read More: Overwhelmed? Need to know what to do first? I know I was, these articles I wrote about what to do first and National Focuses will help. Trade Laws can also help out with Naval Intelligence if you have the right ones in place.

Raiding Convoys

Raiding convoys is how you put a crimp in the enemy’s supply lines but that’s a mission best left to subs. Surface ships make excellent targets for enemy fighters and subs so unless you have air superiority in the region expect to take some losses to your surface ships.

To start raiding convoys assign a group of subs to a task force, select the raid convoys icon on the Battle Plan panel, then right click on the sea region or regions you want to operate in.

To counter subs that are raiding your convoys you can assign a task force to escort convoys. Destroyers are best suited for this order, they’re fast and are excellent at spotting and sinking subs.

Hovering a tooltip over a sea zone will bring up a summary tooltip. It will breakdown your intel efficiency for the sea zone, how many friendly ships are in the zone with orders to engage along with the approximate number of enemy ships in the zone with orders to engage. The higher your Intel Efficiency the more accurate that estimate is. This tooltip will also tell you who has naval supremacy in the sea zone and by what percentage. Air superiority also figures into this percentage.

If combat is occurring hovering the mouse cursor over the fleets will give you details about the fleet’s ships, strength and organization. There is a combat bar over the fleets involved in the combat telling you who the attacker is and who the defender is. Click on it to view the battle

HOI 4 Strategic Navy Map Mode

The Strategic Navy map mode is the best map to organize and deploy your fleets with. When enabled it shows sea zones and shows whether you have superiority in that zone or not, plus it will show the range limit of a task force. It clearly shows what areas of the sea your task forces will be operating in.

Prior to hostilities any sea zones you have a task force it will be highlighted in green and will show 100% Naval Supremacy and 100% Intel Efficiency. It will still be in green if you have naval supremacy during wartime. A red crosshatch means that area is outside the range of the selected task force.

Ships on Patrol are out looking for trouble. This order is given to task forces that are used for spotting enemy fleets. Typically, you won’t allow these fleets to engage the enemy unless you have a clearly superior force. A task force on patrol will usually break off any engagements it might have and wait for a more heavily armed Strike Force to arrive.

If you miss viewing a fleet battle in real time, there are combat results icons in the area of the sea where the battle occurred. Clicking on it brings up all the important details about it, like how many ships each side lost, plus it tells you who was victorious.

Creating Strike Forces is an option I mentioned earlier. If you create a strike force the fleet will stay docked until an enemy is spotted, a good idea if you need to conserve fuel. If an enemy fleet is spotted by your patrol task force a Strike Force will leave port to fight them. A strike force is usually made up of heavier, slower ships. They might consume more fuel but pack a very powerful punch.

Deploying Ships In HOI 4

Auto deploy puts newly produced ships into a reserve fleet. Hovering the mouse pointer over the auto button tells you where the ship will be auto deployed. You can click on the Auto button and decide what theater, fleet or port you’d like to deploy the ship to, just pick it from the list.

Setting Task Force Defaults

Task Forces have several default options that really shouldn’t be ignored that are on the Task Force menu bar. One option is turning automatic reinforcements on or off. Turning this option on always seems like a good option unless your fleet is far from home in enemy waters. Reinforcements might make easy targets for enemy subs on the prowl.

The next option is to allow heavily damaged ships to detach from the task force and return to port for repairs. Similar to reinforcements this leaves them much more open to enemy attacks, especially since they are heavily damaged. I almost never turn this option on, I’d much rather have whatever limited firepower is left on a ship contributing to a naval battle than have it get sunk out to sea. It’s much better to keep a task force together and return to port for repairs as a group in my opinion.

Repair priority can be set to tell the task force  at what point it should return home for repairs, the lower the priority the more damage it will take. I like medium since a high priority means the ships will be in for repairs very often, effectively taking them out of the combat arena much too early and often.

The last option is their engagement rules, which can be set from never engage to always engage, which often leads to a suicide mission.

There are three categories of Doctrines, Land, Naval and Air. There are three paths in each category but only one path can be taken at a time.

Fleets in Being, Trade Interdiction and Base Strike are the three Naval Doctrines in Hearts of Iron IV. The are mutually exclusive, meaning you can only pursue one of the three. That path can be changed but at the loss of any progress in the former tree.

In Naval Doctrines you can either choose Fleet in Being, Trade Interdictions or Base Strike and what you choose will obviously depend on your country and what you want to do with your Navy. Fleets in Being means you build your strategy around battleships. At the beginning you get a 10% increase in most surface ships in your fleets, a 10% better chance of spotting enemy ships plus a 10% increase in minelaying efficiency. There are three branches that can be taken, each focusing on improving your ships in different ways. Unlike the categories in each Doctrine these are not mutually exclusive.

Trade Interdiction is useful when facing a foe with a stronger naval force. The focus along this path is tying up and delaying enemy fleets while destroying enemy supply lines, like convoys. Base Strike centers your naval philosophy around carriers. Each path has its own perks for specific ships so they can accomplish each selected goal easier and faster.

Experience points for the Naval Doctrines are gained through Naval Exercises and some National Focuses, plus combat. Military staff also provide daily gains in experience points. Experience points are capped at 500 so it’s best never to reach that cap or you’ll be losing out on improvements that can be made to your Navy.

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One final point about Naval Doctrines. Although the three paths are mutually exclusive to each other they can be changed. The drawback is that you lose all the advantages you had in the former path, plus there is no refund to experience points.

Rich Gallien

I've always liked board games like chess and PC games, especially space based strategy games, which lead to the creation of this site. I hope you enjoy it as much as I enjoyed creating it and updating it with new games!

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