Or, in a realistic sense since you seem a bit exceptional:
Group of local white guys, no real strong political opinions, have some uniting factor and want to avenge something. Maybe the dad or uncle of one of those kids killed by a nigger - they decide "Fuck this, I'm going to get my hands dirty."
So they do. And it turns out it is WILDLY popular. The guys get away with it, and decide "Wow, everyone really liked that. Maybe we should do it again."
So they do.
More people start copying them, seeing the amount of praise they get.
Then come politics - they're not just some dudes with rifles, now they're X Political group - so one of them gets talking to someone like
@NEETzsche who makes posters, helping to organise shit and funding starts coming in from others, eager to support it but unable to for one reason or another. People who
don't want to get their hands dirty.
You seem to have absolutely no fucking idea how paramilitaries or wars work - I bet you're one of these retards who thinks America was a strong military power in WWII, rather than a strong logistic power.