Bordering fortresses create a highway for the AI?

[Grubnessul]

I know the topic has been done to death, but I always assumed the complaints were overblown. However, playing as Russia, I got a bit into a fight with the Teutonic knights. I trusted that my fortresses would stop them for a while as my troops gathered to absolutely crush them, however, they just totally ignored everything and happily marched on to St. Petersburg and then into Finland. They didn't even stop to refuel or buy some Russian gum underway. Which is rather ridiculous... Aren't fortresses actually supposed to stop someone from just racing through your lands?

Screenshot (with beautifully drawn arrows) and savegame attached.

 

[I_am_Nemo]

Generally speaking, overlapping ZoCs and ZoCs bordering other nations lead to weird scenarios. That said, I'd give a hearty "WTF" if I saw that happening to me.

The first condition to check is whether the forts had garrisons; if the war just started within the month, it's possible they got all that way before the forts got garrisons and got ZoC up, but that seems unlikely.

Barring that, I can only assume the Luki fort messes with the Polotsk fort, the Polotsk fort returns the favor, and then the overlaping Luki and Pskov ZoCs mess each other up and allow them to move from Kholm to Novgorod. Your capital fort in St. Petersberg is only a level one from the looks of it, so that won't have any ZoC at all. Exactly why those interactions happen that way, I don't know, but similar configurations tend to produce similarly bizarre results.

The moral of the story? Try to leave at least one province space between all your forts; maybe two, and layer them deep if you really depend on them. Otherwise, never trust a fort line until you see the enemy get stopped by it.

 

[makaramus]

at inside of your country it can be even good thing to have nearby forts since enemy cant leave zone of control unless they tring to reach friendly zone. in this case you gave them way to reach sweden
dont do it at borders yet not end of world near your capital area

 

[Toso]

I am pretty sure that this video will help you to understand ZoC better:

My personal opinion is that the forts most of the time are useless, unless you use them for reducing devastation and maintaining army tradition.

 

[Ulfing]

I am pretty sure that this video will help you to understand ZoC better:

But it doesn't answer the question.

The screenshot and the savefile shows that the movement is impossible. At first I thought it was because you only turned on the first few forts 2 month ticks ago, which is long enough for the army to travel there, but Pskov would have then blocked their movement (that's on 3 months worth of garrison). Beyond that though Novgorod should certainly have stopped them as Sweden isn't friendly territory they can bounce out of. As the ZoC video shows, touching a fort ends the ability to skim ZOC unless the return province is a sea tile or borders the enemy (i.e. the Vilnus fort there is useless beyond making the province take longer to siege down).

Are you positive that is the route they took? Any details about when the forts were turned on?

Unless anyone else can see an explanation in the save file this looks a good example for the devs of "funky" behavior. Because if you tag switch to the teutons its clear that movement is impossible.

 

[erneiz_hyde]

Another possible scenario is that they have been moving since before the DoW.

 

[Ulfing]

Another possible scenario is that they have been moving since before the DoW.

Pretty sure units outside of your territory get insta-black flagged unless currently on the territory of someone you were already at war with. Entering Sweden wouldn't have reset it.

 

[erneiz_hyde]

Maybe their units weren't on Russia on the moment of Dow, but is already on the way to Sweden since before that, with some sort of conditional military access magic from somewhere.

 

[Nostalgium]

As far as I can tell, it's the Luki fort that's creating issues. Braslaw is in a shared ZOC with Polotsk and Vilno, so the Teutons are attacking into the Polotsk fort from the shared ZOC. WAD. Then, since Luki borders Polotsk, that puts Polotsk within the ZOC of the Luki fort - even though Polotsk has a fort of its own. Since you can always move into a fort in which ZOC you are, they move on to Luki. Luki is then in the ZOC of Pskov, and Kholm is shared between Pskov and Novgorod - so they move within the ZOC of Pskov to Kholm, then from there attack onto Novgorod. How they then exit Novgorod onto St. Petersburg is a mystery to me, but presumably it has to do with bordering forts weirdness.

If you destroy the Luki fort, it would remove Pskov and Polotsk from its ZOC, and armies would halt there as you no doubt intended.

 

[Kergan]

There's a known "bug" whereby if a fort is mothballed when the war starts, it exhibits no ZoC. Assuming your forts were mothballed when you declared, the TO could have given move orders before ZoC appear - and once they do, existing move orders aren't re-evaluated, leading to the impression that the AI ignores ZoC (and so can you).

 

[browd]

^ This. And when you do this (initiate move order at the beginning of a war directing an army to head to a specific fort location deep in enemy territory), you cannot cancel or change that move order once the intervening mothballed forts are activated -- your army will march inexorably to its destination, ignoring ZOC of the formerly mothballed forts.

 

[erneiz_hyde]

That bug works even if the fort was operational afaik. The existing move orders simply aren't re-evelatuated in regards to fort blocking. So if they already moved before the war, then they will keep moving even with the forts, unless you intercept them.

 

[Sharples88]

There's a known "bug" whereby if a fort is mothballed when the war starts, it exhibits no ZoC. Assuming your forts were mothballed when you declared, the TO could have given move orders before ZoC appear - and once they do, existing move orders aren't re-evaluated, leading to the impression that the AI ignores ZoC (and so can you).

The same can also happen if you had access to the enemy country somehow (I.E conditional access) and made your move before entering a war on them/ally. You can go through any fort because the movement never gets cancelled. I've already reported this and the Mothball oversight but it doesn't seem like they're working on fixing it. If you cancel the movement while at war and try the same path again, you won't be able to do it. Clearly it's not intended, and *probably* why the above is happening. Reman doesn't explain it in the video but in the description he does.

Just add it on to the list of fort problems.

 

[Ulfing]

Well that seems like the most reasonable answer then, as all the forts in that screenshot have <1000 garrison.

 

[IndraSunrise]

There's a known "bug" whereby if a fort is mothballed when the war starts, it exhibits no ZoC.

Why would this be a bug?
Its mothballed. Why on earth would a building without any troops have any effect at all? It's a tourist attraction. Same reason why it doesn't reduce devastation. If you want the benefits, you have to pay for them.

 

[Sharples88]

Why would this be a bug? Its mothballed. Why on earth would a building without any troops have any effect at all?

This is an oversight in of itself, a fort with zero troops can still exert ZOC just by clicking the button. Although you can get thorugh that by making the movement BEFORE they unmothball the fort.

The AI must have made the movement before they turned on the forts (or it was automatic). Even if they have men in the forts, it still doesn't stop them until they recalculate their movement. All that needs to be done to fix this is to force-cancel the movement that is now an illegal move.

 

[Kergan]

Why would this be a bug?
Its mothballed. Why on earth would a building without any troops have any effect at all? It's a tourist attraction. Same reason why it doesn't reduce devastation. If you want the benefits, you have to pay for them.

I've no problem with the notion that mothballed forts don't exhibit a ZoC. But if, by the time an enemy troop arrives, the (now existing) ZoC still doesn't apply it's clearly a bug. Plus, as already noted, a fort with zero men in the garrison will still exhibit a ZoC. So there's a clear inconsistency here somewhere.

 

[Leon12]

Your forts in Polotsk and Luki have overlapping ZoCs, which means that an army (any army, player or AI) can move from one fort to the other. A "highway" right into your territory is precisely what it is. Don't overlap ZoCs and armies will indeed be forced to siege down a fort in order to progress.

 

[Less2]

The only reliable fort setup is to have 2 provinces between forts and to have all neighboring provinces be owned by you. Anything else will give head-scratching results somehow, from AI being able to dance to weird places, one-way forcefields, armies that become trapped (and stack-wipable upon any loss) when fort control flips, and so on.

 

[Grubnessul]

That's very helpful, thanks guys.

(still, it's stupid, but at least I understand what went on here)


((and yes, the puny Teutons were mercilessly crushed!))