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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.

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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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What about landmines for coastal provinces? They should reduce effectiveness of naval invasions. Denmark didn't clear its beaches completely of mines until as of a few years ago. Engineers and anti-mine tanks would be useful for clearing them.
 
A few things - I know that the cleanup was a big deal in reality, but doing it like this avoids tedium of cleaning up in peace time. It fixes a bunch of exploits and stops numbers from going truly wierd for a 3rd world war. especially with sides swapping allegiences and suddenly not being aware of where mines are etc (as noted above. stuff tends to be made public). I didnt feel it would add very much. I mean technically we could have a fast decay instead, but I wasnt convinced it would really come into play and be worth the effort.
Wouldn't removing mines after a war ends prevent you from continually mining your coastal waters in preparation for a future war? It would mean that the UK for example would lose all their mines in the channel, allowing the soviet to invade more easily which certainly wouldn't have made sense.
 
Wouldn't removing mines after a war ends prevent you from continually mining your coastal waters in preparation for a future war? It would mean that the UK for example would lose all their mines in the channel, allowing the soviet to invade more easily which certainly wouldn't have made sense.

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
 
Wouldn't removing mines after a war ends prevent you from continually mining your coastal waters in preparation for a future war? It would mean that the UK for example would lose all their mines in the channel, allowing the soviet to invade more easily which certainly wouldn't have made sense.

No, but you can bet than as the UK, I will lay up starting septembre 1939 some surprises off the coast of Singapore (lots of them).

This said, two general observations.

Water mines, like land mines are a very potent element of defence when integrate with other weapons. A stretch of sea that is just barred by mines is at worse at inconvenience for warships.

Mines laid by submarines, even dedicated ones, required major efforts to be worthwhile (or lots of submarines). A rare historical example, the French Saphir-class, could carry 32 mines. While it was certainly useful to lay the mines underwater, you are not going very far with 32 mines and six submarines (who were not very good at tasks other than minelaying), while a surface ship could carry easily several hundreds.
 
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No, but you can bet than as the UK, I will lay up starting septembre 1939 some surprises off the coast of Singapore (lots of them).

Which would be historically plausible - the British started laying defensive minefields around Singapore on the 4th of September 1939, and continued to replenish and reinforce its defensive minefields right up until the start of December 1941 :). They shouldn't have been surprises though - consistent with International Law (the aforementioned Hague convention) these minefields were declared. Their role wasn't to surprise Japanese naval forces, but to either slow them down (while sweeping them) or force them to sail around them (funnelling their ships into other areas).

Water mines, like land mines are a very potent element of defence when integrate with other weapons. A stretch of sea that is just barred by mines is at worse at inconvenience for warships.

Like most weapons, they're definitely better when used in conjunction with other weapons (some minefields sole purpose was to channel traffic elsewhere to make it easier for ships/subs to intercept them) but mines by themselves did a huge amount of damage. The British aerial minelaying campaign in the Baltic from 1941 onwards (and particularly later in the war, as more aircraft and better mines were available) caused signifcant disruptions to German Baltic maritime and naval traffic during the war (particularly later on, but even from the get go it tied down significant resources keeping sea lanes clear).

Same story for the German minelaying campaign in British waters earlier on - HMS Belfast was knocked out of action for years by mines alone, and while the Channel Dash wasn't a "mines only" operation, the impact of the other British attacks was irrelevant to the success of the mines in effectively knocking Gneisenau out of commission for a long period of time (with air attack in port looking after the rest).

Edit: Also, minelaying submarines proved quite successful (particularly for the US early on, given the poor quality of their torpedoes). I'm going from memory, but I think around 1 in 8 of US sub-laid mines was either a hit or a sinking - and given their fleet subs could carry 40, that's a pretty good haul. Submarines, like any weapon, need mass to impact at the strategic level, and there's no way you'd use them to lay defensive minefields (which is where auxiliaries like car ferries would lay hundreds at a time), but for offensive fields, particularly in areas with significant enemy air cover (eg, German sub minelayers off the US East Coast) they were quite effective and sometimes the only option.
 
@TomaszKowalczyk
Its so great that we are getting mine decay. Now if there were defines
MINE_DECAY_PEACE = 50,
MINE_DECAY_WAR = 0

then modders could potentially activate it for wartime as well this would be perfect. Do you think that modders would be able to enable equipment for sea mines? So while mine-laying the Sea Mine equipment is being reduced.
 
No, but you can bet than as the UK, I will lay up starting septembre 1939 some surprises off the coast of Singapore (lots of them).

This said, two general observations.

Water mines, like land mines are a very potent element of defence when integrate with other weapons. A stretch of sea that is just barred by mines is at worse at inconvenience for warships.

Mines laid by submarines, even dedicated ones, required major efforts to be worthwhile (or lots of submarines). A rare historical example, the French Saphir-class, could carry 32 mines. While it was certainly useful to lay the mines underwater, you are not going very far with 32 mines and six submarines (who were not very good at tasks other than minelaying), while a surface ship could carry easily several hundreds.

Exploit incoming!
Italy never finishes the war in Ethiopia (or for NF sake dow another minor) and uses her fleet to mine the entire globe.
Since there's no mine decay in war time, when Italy joins WW2 in 1940, 4 years of mining the globe could send the entire Allied fleet to the bottom of the oceans.
Concentrated production of mine layers from 1936 and tech rush included.

That'll be the first thing I'll do in MtG!!
 
Exploit incoming!
Italy never finishes the war in Ethiopia (or for NF sake dow another minor) and uses her fleet to mine the entire globe.
That'll be the first thing I'll do in MtG!!
Mined blown!
giphy.gif

Mare Minum!
Italia, L’Italia s’è desta

Thats another reason I hoped for the define so we can also potentially mod it easier for stuff like Multiplayer. And a slight wartime decay would be a natural limiting factor for extremely high numbers of laid mines. Like if you build extreme numbers of minelaying destroyers and mine the whole pacific as Japan ever since war starts with china for happy US island-hopping.
A large number of laid mines would then mean that decay increases to a level where maybe you can't even sustain it anymore. This would maybe be even be more relevant if you mod sea mines as actual equipment that you have to produce.
 
Exploit incoming!
Italy never finishes the war in Ethiopia (or for NF sake dow another minor) and uses her fleet to mine the entire globe.
Since there's no mine decay in war time, when Italy joins WW2 in 1940, 4 years of mining the globe could send the entire Allied fleet to the bottom of the oceans.
Concentrated production of mine layers from 1936 and tech rush included.

That'll be the first thing I'll do in MtG!!
Good call, because PDX makes these kinds of oversights all the time and honestly I wouldn't be surprised if this would've made it to the release of MtG if someone hadn't posted about it. Let's hope @podcat reads your post.
 
Will 'friendly' mines have an effect on friendly shipping, like making ships take longer to navigate the area based on the number of mines as you have to go around the excessive number of known mine fields, or will there be a cap on how many mines you can lay?
 
Exploit incoming!
Italy never finishes the war in Ethiopia (or for NF sake dow another minor) and uses her fleet to mine the entire globe.
Since there's no mine decay in war time, when Italy joins WW2 in 1940, 4 years of mining the globe could send the entire Allied fleet to the bottom of the oceans.
Concentrated production of mine layers from 1936 and tech rush included.

That'll be the first thing I'll do in MtG!!

They could put in something about not being able to lay sea mines when you are at war with a land-locked country.
Or huge political power and relationship penalties for mining off neutral coasts
 
Good call, because PDX makes these kinds of oversights all the time and honestly I wouldn't be surprised if this would've made it to the release of MtG if someone hadn't posted about it. Let's hope @podcat reads your post.
Let's hope not! My evil plan thwarted cause I couldn't keep my mouth shut. Now I know how James Bond villains are feeling!
 
They could put in something about not being able to lay sea mines when you are at war with a land-locked country.
Or huge political power and relationship penalties for mining off neutral coasts
Uh, then I dow Cuba...
About the neutral thing: that won't work either for too many reasons.

What I'm definitely looking forward to are extreme strategies like:
- mega U-Boat force that will mine the Atlantic gap and the US coast from 1939 onwards plus the routes to future Soviet LL.
- tech rushing mines like there's no tomorrow

Oh, now I'm excited for MtG more than ever!
 
I think there is now time to make the naval UI a bit more clear. If we now have real need to include several types of DDs (AA, ASW, minelaying, minesweeping) in one fleet, it would be really handy to tell these various types at glance when organizing fleets.