• We have updated our Community Code of Conduct. Please read through the new rules for the forum that are an integral part of Paradox Interactive’s User Agreement.

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.

rep2.jpg


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
 
Last edited:
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.

View attachment 399112

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.
View attachment 399109

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.
View attachment 399110

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.

View attachment 399108
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:
View attachment 399113

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.

View attachment 399114

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
I proposed this once for HoI2 many years ago. The scheming villain in me rejoices!

4654227-4325468156-1a844.jpg


tenor.gif


tenor.gif
 
Last edited:
Will the AI be able to use all of these new features? Two years after release, the AI is still honorably sending millions of soldiers to die attacking mountain fortifications in every game I have played, and last I checked you were hardcoding the German AI so that it would at least stop getting bogged down for years frontally attacking the Maginot Line. So will the AI be able to use naval mines, the ship designer, and other functionality, or will it continue the parade of artificial stupidity?
 
Will you be able to turn of this feature if it proves to limit the naval combat (don’t want the German navy to sink by itself!)?

Also some good onces:
-this new feature is going to be mine blowing
-peace of mine
-mine kampf
-those guns are mine
-mine the gap
 
It may had a few detail different, which isn't that unusual by the way, from the true story. I knew that before I went to watch the film and I still enjoy it. Not sure why you want to call it drivel but sure OK.

it was the first thing that came to mind when I thought of a HOI4 naval rework present around u-sub. Dunkirk don't count since most of the film were in shallow sea and air and on the beach. If you can find a better movie to suit this DD topic I am open to it.

It's pretty much a fabrication which is loosely based off of real life. Important people and facts were omitted, others fabricated for dramatization purposes (like the scene you thought of, which never happened), much of which crosses over into slander. The movie is a joke, and anyone that wants to know about Turing, the enigma machine, and how its various iterations were deciphered should just avoid it.
 
will start to disappear over time once a nation is completely at peace

Do mines degrade over time anyway? I would imagine that a mine laid in 1938, even if your nation was at war constantly until 1950, might not be operating at its best conditions. Will tech levels be recorded per mine or will getting a damage upgrade tech for your mines even if already laid?
 
Cheers for the DD Podcat, mine levels of excitement are off the charts :D. Am a big fan of this being in the game, as mine warfare during the period was strategically important and often quite dramatic to boot!

For this week's DD, soooo many pics - but here's one I stumbled across recently - a Kriegsmarine officer decorating their mines before laying them off the coast of Britain :)

Mine art small.jpg



- The Ship Designer isn’t unfinished, it’s just a bit shy

Can't wait to see this :D.

In WWII, how many warships were sunk by mines?

From Brown's Warship Losses of World War Two, 200 warships were sunk by mines, compared with 263 by surface action, 330 by sub torpedo and 561 by air attack. Of those 200, 79 were DDs (or HoI4-worthy TBs) or above that were not sunk by friendly mines.

Were the historical mine laying strategies different enough to be worth simulating?

Minefields during the war varied substantially. Some examples off the top of my head:
  • Germany used offensive minelaying by subs, DDs and aircraft off Britain's coast to severely damage coastal convoys and damage/sink warships.
  • Britain used defensive minelaying to effectively block the channel to submarines and make passage by surface warship very dangerous (I think it was Gneisenau that struck two mines in the channel dash, and iirc never saw active duty again, although the mines weren't the only factor there by any measure)
  • Britain mined part of the Denmark Strait (between Iceland and Greenland) limiting the channel which Bismarck and Prinz Eugen could take, making them easier to spot by patrolling cruisers.
  • Germany, Denmark and Sweden all took part in mining the Danish straits (the actual straits around Denmark), effectively blocking the Baltic to British submarines.
  • Germany also laid a mine across the mouth of the Skagerrak, making passage into there very dangerous.
  • Offensive aerial mining by Britain and the Soviet Union in the Baltic limited German submarine training, and damaged key resources being transported from Sweden and the supply of Germany's armies on the Eastern Front (although in HoI4 these last two don't benefit from using the sea :().
  • Italy heavily mined the Sicilian narrows, and it was mines, submarines and MTBs that did the key damage to Operation Pedestal, not aircraft.
  • Italy also mined other parts of the Mediterranean - their defensive minefields off the African coast damaged or disabled more than half of Force K (three CLs, three-to-four-ish DDs, off the top of my head but can look up) in one incident.
  • The US used offensive minelaying to substantially damage Japan's trade, to some degree using mines to compensate for torpedo reliability issues at one point.
  • The US used offensive, primarily aerial minelaying to cripple Japan's economy (which relied heavily on coastal transportation of goods) in April to June 1945, doing far more damage to Japanese economy than the atom bombs.
  • Germany used submarine minelayers to lay fields off important US east coast ports.
  • Germany laid extensive minefields in the Channel to protect against invasion (there were over 200 minesweepers used in the operation to clear channels to the Normandy beachheads).
The effort required to lay, and clear, these minefields varied substantially, and the various warfighting tools required varied as well (for example, Germany stationed night fighters in Denmark to counter British aerial minelaying in the Baltic - while Germany used long-range submarines to lay minefields off the US east coast, and Britain had hundreds of craft regularly employed to clear minefields off their coast).

I agree it's important that the gameplay works, but there's absolutely no question that minewarfare was strategically important enough to merit representation in HoI4, and varied enough to attempt it as a gameplay mechanic. We'll have to wait and see on the gameplay though, but the early signs are promising :).

no, war time only. I think there are still some pretty heavy laws against that

In peacetime I think it's alright to lay mines in ones' own territorial waters - Sweden went as far as to mine between its east coast and Aland (in an attempt to keep Soviet subs out of the Gulf of Bothnia) - but definitely agree that from a gameplay perspective it makes by far the most sense to limit it to wartime. The impact on coastal shipping generally meant it made no sense at all to lay mines off ones' own coast in peacetime unless things looked really grim!

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.

Too right - over 68,000 mines and explosive anti-minesweeping devices were laid in the Gulf of Finland alone during the war, and caused all sorts of trouble for the Soviets. The impact of German mines on the evacuation of Tallinn was brutal on the Soviet Baltic Fleet.

if their numbers are accurate (there are some sources mentioned on site), only allied ships though.

Quite right - mines also took a heavy toll on German (and requisitioned by Germany) shipping in the Baltic, and Japanese shipping in the Pacific.

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's important to keep in mind that friendly non-military shipping needs to be made aware of defensive minefields to prevent economic suicide, so these were well publicised and easy for both sides to track.

For offensive minefields, the 1907 Hague convention in mine warfare (very impressive reference earlier @Catharsis27 :cool:) required mines laid outside of territorial waters to be made public, and by-and-large the Allies did this, at least early on. Germany was a bit more circumspect in this regard, but generally, enemy aircraft and ship sighting reports, mislaid mines (aerial mines dropped on land by mistake, or mines that break free of their mooring and drift on the surface) and the actual run-ins between ships and mines themselves meant that most minefields were pretty well known.

It is the case for some of the smaller fields (for example, a minefield laid by a single sub outside a port, without any mines breaking their moorings - or if they were all ground mines - and they were no accidental explosions*) that the first time anyone knew of them was when a ship exploded, but I'd argue this is a bit too 'small level' to be represented in HoI4. It's definitely the case that knowing exactly how many mines have been laid is more info than anyone had (at this point in history, nations couldn't monitor how many of their mines were still in place, let alone the enemy's) but I see this as a reasonable balance between gameplay and historical plausibility.

* These were fairly common - the bad weather that hindered the Allies after the Normandy landings also exploded many of Germany's recently-laid pressure mines.

Good idea by the developers but its lot more than just to add mines to game.

There's definitely a lot more detail that can be added (and if the devs wanted to add individual types of mines, researchable mine components, researchable minelaying techniques, researchable minesweeping techniques and doctrines, production of individual mines, mines designed against specific ships (eg; anti-submarine), post-war mine clearance, minesweeping countermeasures, mine 'killswitches' and a bunch of other things I'd probably be as happy as a pig in mud), but I suspect 99% of the rest of the HoI4 fanbase would be finding it a bit hard going - it's important the game balances the amount of detail in one area like minesweeping with that in others (eg, air warfare) to keep everything working well together.

btw. seems @TomaszKowalczyk actually added mine decay in peace time :D he had forgotten to tell me. So mines do not actually instantly dissapear, there is some time between if another war kicks off. I'll update the diary itself

Very cool :cool:. It might even be worth having a set 'constant decay' (as minefields did decay over time, I think I have some examples in terms of stats floating around somewhere if they would be helpful?) but some decay in peacetime would be good.

Oh, nice. This should make Axe99 a happy man.

Mines? I'm not the least bit interested in naval minewarfare....not! :D Deffo all smiles over here, this (as well as managing access to different sea zones, fuel and I suspect the ship designer) should make the naval side of HoI4 heaps more interesting and engaging :D.
 
Last edited:
Do mines upgrade? or will you have a mix of new and old mines in one field?

Having mines stay forever would give fleets something to do in peacetime, currently the NZ navy is still clearing ww2 mines so presumably they don't fade that fast in the real world?
But mainly, ships don't have alot of duties in peace time in the game.
 
You specifically mentioned the evacuation of the Dutch Royal Family here... earlier, a Government-in-Exile feature was teased...

Also, will landmines become a feature later on? They could pose an added risk for invading armies, and give a large kick to attrition, especially when added in areas with forts.
 
That's ignoring the biggest problems with mines. That they don't go away once the war is over.

That's the biggest problem with so many history gamers, they don't understand: gameplay > realism

The result of such thinking is called "BICE".
 
@Axe99
Thanks for the convincing explanation. Now I'm looking forward to the feature. Mine strategies somehow managed to evade my attention before.
 
@Axe99
Thanks for the convincing explanation. Now I'm looking forward to the feature. Mine strategies somehow managed to evade my attention before.

No worries at all - a lot of general books on WW2, and even the naval side of WW2, give mine warfare short shrift, so it's easy to overlook. There's also not many books on it, so it can be a bit of a hunt tracking things down. Hopefully HoI4'll help give it the prominence it deserves, while also making the naval game a bit more strategic* :D.

* Noting it's already strategic - this statement isn't trying to suggest it isn't.
 
Also, will landmines become a feature later on? They could pose an added risk for invading armies, and give a large kick to attrition, especially when added in areas with forts.

I would say land mines are already in the game, though abstracted into the dig-in bonus for division. They are more of a tactical weapon.

Sea mines on the other hand usually has a more strategic purpose by denying large areas of the sea to an enemy and restricting enemy movement on a strategic level. Axe99 covered this much more eloquently than I could .

mine warfare during the period was strategically important and often quite dramatic to boot!

The drama was mostly during mining operations though. At least sometimes. The standard procedure was mostly put to sea at day, reach designated area by night to avoid detection, drop the load and get back home, usually without ever sighting an enemy.
The sweeping part was a peculiar mix of incredibly dangerous an mind-numbingly boring at the same time. I think sweeper crews had one of the most important and least enviable jobs during the entire war...
 
#land mines
Aren't the provinces way too large for the tactical nature of land mines?
They were used to channel the enemy attack into a desired direction, to protect flanks or to stall the enemy advance while conducting an orderly retreat.

Land mines work better in Panzer General scope games.
 
I would say land mines are already in the game, though abstracted into the dig-in bonus for division. They are more of a tactical weapon.
Yeah everywhere there were engineers there were also mine fields laid so basically in every division you have mines.
Imho you can't really represent hand grenades either in HOI4 they are just there. You could say they are abstracted as part of the defensive bonus for engineers.
If at all you could represent AT mines as part of some AT equipment gives Infantry brigades a small bonus to hard and pierce BICE is doing it that way but even they aren't specifically representing AP mines.
 
Last edited:
I for one welcome our new naval overlord!

lol - I'm just an enthusiast, there are folks in these parts that know more about naval stuff than I :). My main claim to fame is posting naval-related images, and on that note, here are some brave, nerves-of-steel types defusing a German mine that was accidentally dropped on (by the look of it) mud flats or similar (which was a very dangerous job):

Defusing an influence mine small.jpg