Hammer Editor: Make Out-of-sight Enemy Target Player [closed]

I'm making a map where you work with the combine against the rebels. Everything is working pretty smoothly, however I am unable to get the rebels to start a battle automatically.

I have the enemy rebels hiding behind the corner of a wall, which is out of sight of the player and unreachable without noclip (there is an invisible wall that stops only the player). I have got something which is meant to trigger the battle, however the rebels do not seek the player or the combine. In the past to start battles to test the AI nodes and such, I have had to noclip past the wall and shoot one of the rebels (or allow them to see me) which then lets the spawning and battle happen.

I'm wondering how I can set a trigger that tells the rebels to start spawning and trigger the battle, bringing them all out of hiding. One important thing to note is that the player is a standard soldier, so they cannot be prioritised as a target for the rebels to shoot.

I know a little about Standoffs, however I do not have full knowledge.

PS if it helps, this map is being tested in HL2, but will be used in GMod.