Hi everyone! It's time to start talking about how the naval aspects of the game are changing with Hearts of Iron IV. There are a lot of aspects of naval gameplay, so we will be splitting this up in several diaries. Strategic warfare and details on missions will be in later diaries. This one will focus on direct combat and the general idea.We had a few goals when designing naval mechanics for HOI4. We wanted it to both be able to handle the case of German surface raider ships relying on firepower and speed to tie up a large portion of the royal navy with a few ships like what happened early on in the war and the massive naval battles of the pacific between Japan and USA. We also wanted different ship types to be able to interact with each other and not make, say, convoy raiding a completely separate system.What makes naval action so different from land is that the position of everything is not precisely known. So just because you know there is a German ship in a sea zone doesn't mean you can find it before it leaves.To solve all this ships use both strategic areas (see Diary 7) and exact province locations. A task force of ships can have missions in a strategic sea area and this can cause events to happen. A naval event can be fleets coming into contact, or a raider or submarine finding enemy convoys. Once one of these happen the location is displayed on the map as a combat. Each mission (we'll talk more about these in a future diary about strategic warfare) controls how the naval task force is spread out. So for example if you set your task force to patrol an area they will spread out as much as possible increasing chance of finding an enemy, but because they are spread out only a smaller part of the fleet will actually make initial contact with the enemy. If you set up your task force on more of a search & destroy mission they will stick together and be much less likely to find lone ships, but when they do run into something most ships will be there for the initial confrontation. Typically this is something you'll want if you are fighting a large enemy fleet. Notice how I said initial contact, that’s because naval battles can be longer affairs of positioning. Lets look at a picture:The area in the middle is the active combat area with the ships distance to the center showing their relative distance. To each side is an area showing part of the enemy navy on the way. Depending on your intel you may or may not know what is coming (or just that *something* is coming) there. As an example from history here take a German fast heavy cruiser like the Admiral Graf Spee, hunting British shipping early on in the war. The British will be hunting for it in turn, but are spread out (so they can actually find it) so it will actually only face a smaller part of the royal navy at a time. Having strong armament and speed means that it may be spotted by a British cruiser with a larger fleet trying to get to the location of the battle to give support and the Graf Spee has a chance to take out that cruiser and get away before the rest arrive, which if it happens means they need to locate it again. This should hopefully mean that even small technically advanced navies have a place in the game.So what about more even combat, like shown in the picture above? When large fleets meet the game will divides them up in groups of ships that will exchange fire because they may enter the battle from different directions and at different times depending on spread etc. Each of these groups is optimally one or more capital ship with a decent ratio of screen ships like cruisers and destroyers. Screens are very important because they defend the larger ships from enemy small ships that can carry torpedoes. Torpedoes have lower hit chance but when they hit they do a ton of damage on large ships. We have tried to make sure each ship type has a role to play in the battle, so for example destroyers are cheap screens that can evade large caliber fire, add anti-air capabilities and let you detect and neutralize submarines. Cruisers are good at at taking out other screens and carry torpedoes making them dangerous to capital ships if they get close enough. Heavy cruisers, Battlecrusiers and Battleships can take a lot of hits and carry a lot of firepower and Super Heavy Battleships add Cool and Flair to your fleetCarriers work like a mobile air field and can carry a variety of carrier-capable planes to project damage across the battlefield. Finally Submarines are good at destroying convoys, but can also fill a role in regular fleet combat should the enemy be low on submarine detection. A submarine starts out hidden and is either spotted if it gets too close to a destroyer or after firing a torpedo after which it will try to escape. It won't be an effective weapon against an enemy with a proper fleet, but unescorted capital ships won't have much defense. Again, another thing in favor of trying to develop a balanced fleet rather than specializing.