Remove siege buildings forever in game

[d4kks]

A game removes siege buildings (siege and castle_siege in EDB.txt) or siege units (Ballista, Catapult & Trebuchet) from a recruitment forever after a historic_event "gunpowder_discovered". Is it possible?

[Sar1n]

Yes. You can use event counter from campaign script as condition in EDB. For example, this is from EBII:

recruit_pool "hellenistic infantry hoplitai haploi"  1  0.03  1  0  requires factions { cul_1, cul_3, f_pontos, } and event_counter ecThorakitaiReform 1 and not hidden_resource baktria and hidden_resource eastern and hidden_resource hellen2 or hidden_resource hellen1
                recruit_pool "hellenistic infantry hemithorakitai"  1  0.03  1  0  requires factions { cul_1, cul_3, f_pontos, } and not event_counter ecThorakitaiReform 1 and not hidden_resource baktria and hidden_resource eastern and hidden_resource hellen2 or hidden_resource hellen1

This shows one unit-Hoplitai Haploi-recruitable only after event Thorakitai Reform fires, while the other unit is recruitable only before.

So if the gunpowder discovery is coded as an event, and I believe it is so even in vanilla, you can use it. Just make sure that the buildings you're trying to remove are not a prerequisite for something.