For a map of mine, I'm trying to find a system that detects if you're allied or not so that i can keep everybody allied without spamming ally so you can't kill each other. I tried several different things and i can't figure it out.

use "foes" and "allies" in the condition.

You can detect a unit, or a death count, or some other variable so long as it remains constant throughout the game. If player 1 is the only one with a protoss forge, then detect if "foes command 1 protoss forge", or vice versa. If you don't have anything like that, create a trigger for each person, and set the death count to the number. For example, player 1 sets death of cantina to 1 at the start of the game, player 2 sets 2, so on and so forth.

Well, using your info rockz, i managed to get a system working. So this thread can be closed