It's a lazy day for me, I'm too lazy to do things in real life, but I'm too tired to do anything important in Fallout, so I've been screwing around with console commands. I've been having 20 vs 20 battles, hell I had a Vet ranger kill 5 Centurions with a Ranger Sequoia in 5 straight 1v1s. Anyways, some people I've been wanting to fight, just don't turn hostile and I want to figure it out. Some NCR troopers don't engage Praetorians or anybody at the Fort. Is there a command to make people hostile to a certain faction? e.g. BoS and Legion

shoot at them?

*Yes there is a command that can do this.

~
Click on the NPC, then type
setav aggression, 100
Press enter

Ah...
Well I'd say set them as opposing factions, but I see you got an answer (below).

Sorry, I mean I don't want them to be hostile towards me, I want them to be hostile to the other people I've spawned. For example, since I'm at The Fort, I want the people I summon to be hostile towards the Legion. Some are by default, but I don't know how to do that to people who aren't hostile to them.

No. But there is the trigger to do so. I think the base id is 130bf6

This should make the BoS hostile towards the legion.

Hey, it's the NPCWars guy! I'm sure you know all about setting people hostile! I'll try that code.

:) It will spawn a BoS paladin that is allied with the NCR and BoS.