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HOI4 Dev Diary - Railway guns never tire

Hello there, C0RAX again.

It’s time again to reveal some more secret information that was hinted at in the last dev diary. Specifically this week will be revolving around the final part of railways and trains. So without any more need for introduction here are our stars of the show today.

The railway guns.

So to start off I'll go through how you get a railway gun on the map because it’s a little different to normal land units. First of all you are going to want to research railway guns which comes after armoured trains.
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Then you can find it in your production tab just like building normal equipment. But unlike other equipment you build, these production lines are limited to 5 factories and the railway gun won't be added to your stockpile.
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Instead, once completed, your brand new railway gun will appear in your capital, in this way they are built similar to capital ships.
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Moving your railway gun is limited to provinces with railways, and so to get to the front you must have a rail connection. Taking into account the rail conversion time when capturing territory is important as you will have to wait for the big guns to be able to help you out.
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You can also attach railway guns to armies just like with planes and they will attempt to place themselves relative to the frontline. If you have several, they will be distributed where possible to support your army. There is also a quick select button on the army to select all railways guns attached to an army should you need to.
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Finally, the last bit of control understanding is range. Railway guns have a range in which they can support and so from any one point are limited in which provinces they can support. This range is shown by hovering over the unit icon.
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On to combat now, here we can see a combat with a supporting railway gun, we have added the useful icon on the combat progress indicator that there is a supporting bombardment. This new icon will also show if there is shore bombardment happening in the combat.
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The combat effects of railway gun bombardment work just like shore bombardment, causing negative combat stat modifiers to those on the receiving end of the big guns. These modifiers affect both soft and hard attack as well as defense values. Notably, these effects do not stack - it becomes more important to spread out your railway artillery than to concentrate it.
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Finally we need to talk about capture and damage, railway guns can be captured via encircling them and damaged by damaging the railway they are placed upon.

Now railway guns are the biggest guns by far used on land and so it's important that we have representations of those built by the major powers. So now we look at the unique guns for the major powers.

This is the German Schwerer Gustav model you will see when playing as the Germans. It's perhaps the most famous railway gun and definitely the biggest and so had to have a part in this feature.
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This is the BL 9.2inch railway gun, a relic of the first world war but these big guns were kept in service until 1945.
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Following that we have the French Canon de 305 another veteran of the first world war.
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Next up is the USA’s 8-inch Mk. VI which remarkably first entered service as late as 1941!
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Type 90 240 mm railway gun whose claim to fame is being destroyed by the retreating Japanese in the soviet invasion manchuria.
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And finally the TM-3-12, three of these were made in 1938 and were used in the winter war against finland, unbelievably these where in service until 1999 (a whopping 61 years of service)
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Finally here's a cool clip of the Schwerer Gustav firing in game.
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While interesting to be implemented in HoI 4, the Schwerer Gustav gun itself is an absurdity at best, as the effort to fire a (single) round and likely hit a target does not justify the effort to do so.

I found some of this information in some books:
- It took 5 trains to transfer the disassembled gun to the fire location.
- During assembly, the gun needed three parallel sets of rail (to fire "only two")
- Assembly alone took 56h and tied up more than 5000 personnel for operation (not including two AA battailions) for air defense
- Loading time was approximately 45min
- In Sewastopol, of 48 known fired shots, only 10 were closer than 60m to target - with a given theoretical maximum range of 47km
- Material breakthrough:
* Steel 1m
* Reinforced concrete 7m
- Planned use of the barrel to wear out not earlier than 100 shots
* accuracy already suffered heavily after 15 shots due to the charge size

My conclusion - I am going invest into air and rockets.
 
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In my opinion raiway guns schould hawe option of strategic bombartment, Germans use them that way diuring I and II WW. For example we may look on Paris Canon and V -3 project. Also I agree that railway guns may hawe some bunker busting property.
 
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While I am glad to see railway artillery being added to the game, it seems to be as I feared, in that PDX mostly just went for representing the huge railway guns, rather than covering all the bases. The fact there's just one type of railway artillery, and it's hideously expensive, seems to back this up. Historically many small countries fielded railway artillery because it was worth doing. But why would in-game IC-starved minors ever bother with something that costs 800 production cost and a slew of resources they probably won't have? Seems like a fool's errand to me.

During WW2 for instance Finland used at least 11 railway guns: 4x152mm, 4x180mm and 3x350mm. 10 of those were put into service during WW2. I don't see fielding even one in the game being worth it for a minor like Finland, even if we assume one in-game railway artillery unit to be a full battery.

Just like not every plane was a B-29 and not every tank was a Maus, not every railway gun was a Schwerer Gustav.

I would also like to know, can I mod the feature to represent things like coastal batteries? I have a feeling the answer is no because it'll be hardcoded like fuel, but please say I'm wrong on this.
 
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I don't want to rain on people's parade but I'd quite disappointed if Railway guns turns out to be somekind of land based CAS, that applies a flat debuff to enemy divisions in a wide front as that's not remotely close to how they are used.

They are extremely slow firing siege guns used to shell heavily fortified positions and enemy cities behind the front. Which, with the benefit of hindsight, they aren't effective at doing even that.

This is like making strategic bombers, V1 and V2 rockets into close air support.

Something like a directed single province fire support and the ability to fire on strategic targets(like forts) would be much closer to how they are used.
 
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Makes sense. The other side of the coin works fairly well, too. USS Phoenix (I think, or it was one of the Brooklyns anyway) and some destroyers made a lot of trouble for a German armored division near Salerno (or was it Anzio?).
Light cruisers and destroyers have rapid firing guns which are more suited for close artillery suport (provided they have direct line of sight or a spotter). From Wikipedia the Gustav gun had a rate of fire of one round per 30-45 minutes, whereas a single gun in a Brooklyn could theoretically fire 10 rounds per minute.
Battleships guns could also fire fairly fast (a couple of rounds per minute) but because their larger caliber were less suited for close artillery support than cruisers or destroyers (i.e because of the massive explosive power of battleship shells you generally wouldn't want friendly forces close to what you are shelling) . I assume the latter would also be an issue with railway guns.
 
The image with the Schwerer Gustav standing at a right angle to the tracks first made me laugh, but then ask myself, how did they aim those big guns? Did they have to put down new track in the right direction? I doubt the cannon could turn, lest it would flip the whole cart! o_O
 
Going to add my voice to the chorus saying these would be way more fun to deploy in a specialized role, like bunker busting

Another way of looking at it is what makes for an enjoyable gameplay loop. So far all the new supply stuff is desperately needed and will be fun to play with, but given the cost of the railway gun and the size of the modifier they could wind up being a bit over tuned for western europe and as a consequence, annoying. Who wouldn't want inland shore bombardment? At the same time the game needs more methods of dealing with fortified positions. This should go hand in hand with that priority instead.
 
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Going to voice and unpopular opinion: Dissapointed they made them tactical fire support units, something they would be wholly ineffective on. Instead they should be used as a siege unit and fortress buster.

I.e Schwere Gustav would have been a poor unit to shell advancing tank formations (calling in arty is a long process, even during WW2. It is a reason why battleships wasn't used in this role, but destroyers, or why strategic bombers did not provide CAS) but it was used to weaken i.e Sevastopol.

I think HoI4 should include the possibility of pounding rear echelon units (something startegic bombers and battleships did) and saturate those areas.
Most railway artillery wasn't Heavy Gustav though. Much more railway artillery was a way to bring 6-8" guns to bear with very little setup time (such guns would often have a total azimuth mounting and not require the time-consuming process of setting up a turntable or other infrastructure-intensive aiming mechanism) or to bring 11-12" guns much further inland than the navy could ever hope to (and such guns like the K5 absolutely were deployed for tactical bombardment of enemy troops), though these larger guns were just about as likely to be used as coastal defense guns. These guns would usually be called up for large set-piece battles or assaults on (or defenses of) fortified lines.

Also, battleships absolutely did provide tactical support, including doing so further inland than destroyers could. The main reason you'd see more destroyers doing the job than battleships is that there were so many more destroyers.

So yes, Gustav would be a poor choice for shelling enemy troops, but it is an outlier among railway artillery
 
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Aside from my earlier comment about the French 520mm railway gun, it's generally kind of odd to chose a 305mm gun when France only mobilized six such pieces compared to the most numerous railway guns in their arsenal, the 194mm TAZ modèle 70/93 (24 pieces) and 274mm GI. modèle 17 (16 pieces). TAZ basically means it's a turreted gun and GI that it's fixes mount but does not need significant additional anchorage to brace against its own recoil.
 
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100%. Just looked it up and Schwerer Gustav had a fire rate of 14 rounds per day. That's fourteen!

So considering any kind of tactical use for it just bonkers! There's no way it would hit a moving tank 100km away even once if it only had 14 tries a day!
As I mention elsewhere, despite being iconic, Gustav was an outlier. A more sensible (and far more common) railway gun like the French 194mm TAZ modèle 70/94 could do two rounds per minute. Even amongst larger bore railway guns like the French 274mm GI modèle 17 and German 28cm K5, you're looking at about 15 rounds per hour. All of these weapons were far more numerous than Gustav and should be taken as better examples of typical railway guns.
 
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It seems silly that the effects don't stack, even with a decreasing modifier, or stack up to a level determined by combat width. France, for example, likely cannot get many out, but they only need 3 to cover their entire border. Germany being able to have 30 will not help them break the maginot because france's 1 will counter 30 of them.
France *should* be able to get a lot out. Not because they built a lot from 1936-1940, but because France mobilized 106 railway guns they already had for the battle of France (and 46 of these were at least as large as the piece depicted in the model Paradox has made). Most of these guns would also fight on after France fell, with 58 being taken as war booty by the Germans and 19 by the Italians, both of whom used them as part of their own artillery forces.
 
Looks good, but maybe a bit too strong. I think I would have preferred more of an anti-fort role, rather than what feels like land-based CAS.

Will the AI build and use railway artillery?
 
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Loving this development, however I wish there were two types, a superheavy bunker buster with an AoE anti-fort and anti-city effect, along with a more lightweight railway gun that gives the RG effect already implemented here. Maybe in the future?
 
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