You could get the trigger to call a wee script that changes the combatmode of the Resistance units. However, I'm guessing that the Resistance units are guarding something and you want them to go to aware/combat when West is detected.
If that (or something similar) is the case, then the best thing to do is create new waypoints for the guards. In the new waypoints change their behaviour to Aware. Synchro the old, final waypoint with the trigger. Make the trigger type switch
Your guards' waypoints look something like this
MOVE (safe)
MOVE
CYCLE <----- synchro the switch trigger with this WP
SEEK+DESTROY (aware)
CYCLE
Hope that helps