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HOI4 Dev Diary - Mines and Minesweeping

Welcome to another glorious Wednesday! Today we are going to be talking about mines and mine sweeping. Historically hundreds of thousands of mines were laid during WW2 and with Man the Guns you too will be able to do so in Hearts of Iron.

From a gameplay perspective mines do a lot of interesting things. They add more interaction with the naval layer of the game, create a weapon both for smaller naval nations to fight bigger ones, and for big ones to try and limit where the enemy can get to them.

Screenshot_1.jpg


As you may remember from my presentation at PDXCON, I talked about adding a ship designer to Man the Guns. It is not quite ready to show off, but it’s important to know that sweeping and laying mines are something you will be upgrading or redesigning your ships to be doing. Minelayers and Minesweepers are not actually new ship classes. In my screenies I have destroyers that can both lay and sweep mines for simplicity, but as @Archangel85 pointed out earlier “I am probably going to have a ton of different destroyer designs”... anyways, details on the designer is for a future diary when it is done, but hopefully it helps explain some stuff in the proper context.

Mines are unlocked from techs and require ship designs fitted to deploy them. Destroyers and light cruisers can do this, as well as submarines with the correct tech (excellent if you as Germany want to make things even more dangerous for the British at a lower risk to yourself). Mines can also be dropped from the air with later game techs. Both of these unlock new missions for navies and airwings.
mine_techs.jpg


Mines can be made better and better through research. You start off with Contact Mines to unlock them. Then their destructive power is improved with Magnetic and Acoustic mine techs and finally with Pressure mines. At the bottom (heh) you also see two techs for submarine mine laying. The first is just the basic ability, while the second improves efficiency a lot by allowing mines to be deployed through torpedo tubes, thus no longer requiring you to design specialized minelaying submarines.

To get rid of mines you need minesweeper capable ships. This unlocks the naval mission to sweep mines and will slowly work at clearing areas. Minesweepers are also nice to include in your fleets as they will then be assumed to travel ahead of the fleet and reduce the impact of mines on them. I suspect a good design combo will be anti-air and sweeper on screen ships to be your passive defense when in enemy waters.
mine_report_map.jpg


There is also a passive “degaussing” technology that can be researched after Magnetic Mines. This was employed during WW2 to reduce the magnetic signature of ships and thus make them less likely to set off mines.

It is also possible to sweep mines from the air, but this is a late game, expensive technology and unlocks a new air mission for bombers. This was something that was done sparingly and in shallow waters, but for example was successfully done to evacuate the Dutch royal family to Britain.

What do mines exactly do then? Well they blow stuff up! Their explosive results are shown on map as accident reports, and there is a new tab too under the Naval Losses statistics interface if you want to dig into details. As ships operate or move through a zone they will risk running into mines. This can lead both to minor damage as well as outright sinkings. The best ways to avoid this is to make sure the area is swept free of mines, but as mentioned above, having your ships travel with sweeping capable ships makes it safer for all.

mines report.jpg

This is not all through, mines have several passive effects.

Naval superiority - Having mines in an area helps amplify the effects of your navy (after all they can concentrate more effectively knowing where the mine fields are). This can be seen in our new naval area screen, which is the naval equivalent of the state view:
travel.jpg


Other than that and blowing ships up mines will slow down enemy ships (since they need to be more careful) and increases the invasion penalty to coastal area. So mines are both good offensively and defensively.

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Mines can only be laid while at war and will start to disappear over time once a nation is completely at peace. You always know how much mines there are in an area, so you know how to deal with them and take them into account. That means that with the new naval access controls you can tell your ships and convoys to avoid heavily mined areas, but of course this may make it a lot more predictable for your enemies where to hunt. Having an advantage in the encryption-decryption war will also add a certain amount of passive defense against mine effects as you may have some information about their positioning.

See you all next week for more Man the Guns info!

Rejected Titles (for extra good reason this time...):
- This War of Mine
- Vengeance is Mine sayeth the Lord Admiral
- Do you mine’d
- This feature was made in cooperation with the seagulls from Finding Nemo
- Mine = blown
- The Ship Designer isn’t unfinished, it’s just a bit shy
- Minesweeper 2000 Online HD Edition
- Mine over Matter
- Mine the guns
 
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I have question regarding producing mines.
Will be the mines produced in the factories as planes, tanks etc and cost resorces?
Or you send ships to mision and the number of layed mines will only depends on number of ships(and tech etc) withot any production?
 
If I remember correctly the devs have said somewhere that they are planning to add mechanics that resemble the deescalation after the war. Maybe when those mechanics are implemented some of the passive effect could be the disappearing of mines over time? This would make sense while not being something tedious for the player to do.
 
I have question regarding producing mines.
Will be the mines produced in the factories as planes, tanks etc and cost resorces?
Or you send ships to mision and the number of layed mines will only depends on number of ships(and tech etc) withot any production?
We felt this added a bit too much extra to keep track of etc for little gain. We are making sure the "mining module" required to mine from ships is sufficienctly costly instead to model it
 
Nice to see at least some of the technological race that was the Battle of the Atlantic implemented, hope to see more.

I understand the reasoning behind not including dedicated minesweepers, but I hope that some smaller ships make it in nevertheless.
Destroyer Escorts, Frigates and Corvettes were simply too numerous to dismiss out of hand.
 
You always know how much mines there are in an area, so you know how to deal with them and take them into account
WHY? It's extremely illogical to always know about a weapon designed to be unseen. There are huge possabilities for decryption, recon etc application because knowing in advance about enemy mines is the last thing I cound expect from mine implementation.
 
It was extremely important in the Baltic Sea.
The Soviet Baltic sea fleet which was not insubstantial (contrary to popular belief) especially as Kriegsmarine wasn't glorious either was basically crippled by mining not only in losses but also having to camp in ports and such.

As for total numbers this looks nice
https://www.naval-history.net/WW2CampaignsMineWarfare2.htm
Pg2cfU2.png

if their numbers are accurate (there are some sources mentioned on site), only allied ships though. In 1940 its even second place after subs.
Thank you for the chart. It's very enlightening But my question deals with warships being sunk. This chart lists total numbers of ships, which includes merchant vessels. The game highly abstracts merchant shipping while each individual warship is represented.
 
About mine clearing (Minesweeping):

Without GPS signals it difficult and need ages.

Example:

For the purpose of clearing all types of naval mines, the Royal Navy employed German crews and minesweepers from June 1945 to January 1948,[66] organised in the German Mine Sweeping Administration (GMSA), which consisted of 27,000 members of the former Kriegsmarine and 300 vessels.

When the war ended, more than 25,000 U.S.-laid mines were still in place, and the Navy proved unable to sweep them all, limiting efforts to critical areas.[29] After sweeping for almost a year, in May 1946, the Navy abandoned the effort with 13,000 mines still unswept.[29] Over the next thirty years, more than 500 minesweepers (of a variety of types) were damaged or sunk clearing them.[29]

https://en.wikipedia.org/wiki/Naval_mine

As told before mines dont know friend or foe and it doesnt matter if you warn others about them cause the exact locations will be unknown at open sea (with ww2 technology)......

Good idea by the developers but its lot more than just to add mines to game.
 
@podcat Canada has a focus for degaussing ship hulls. Will this be changed with these changes? Currently it just makes subs easier to detect.

Good catch. I'd imagine it might be better as a research bonus/ahead of time or the like then

WHY? It's extremely illogical to always know about a weapon designed to be unseen. There are huge possabilities for decryption, recon etc application because knowing in advance about enemy mines is the last thing I cound expect from mine implementation.
There is a difference between knowing that there are mines in a huge area and knowing where they are. We felt that knowing if the area had a lot of mine or not would be worth it as you'd likely find out farily fast, and it makes it so much easier to display and play against compared to knowing nothing. As noted in the diary encryption/decryption impacts the "I know where the mines most likely are so I can better avoid them" part. Its a tradeoff in abstraction, and with our pretty barebones intel system I think its the best solution.
 
At this rate MTG is shaping up well I might bypass WTT and get this instead
They cover quite different areas, I wouldnt want to play without either tbh.