@SailusGebel@BearlyAlive the tactics. I'd say it's too tactical for a bunch of common folk that banded together because they do criminal stuff, though @Simple_Russian_Boi 's suggestion is plausible.
Problem is, the gang leader is just a freeloader in his free time.
I vaguely remember seeing documentation about gang wars and everyone was saying it was akin to a warzone. The tactics might be cruder, but the basics are the same as city warfare; guerrilla, supply raids, and sieges. All work the same no matter if it's goon or gunny
The gangs in my place are the student ones, not the criminal ones I want to write in my novel. At worst, they can only sucker stab someone in the neck, but no big fights coz the police will kick their sorry asses.