They are on opposing forces with no allies and are set to Enemy Alliance Status /w trigger preserved. Why won't they attack eachother?

Your need to read learn alot about map making for sc i see, The units need to have the patrole order given or you can run the random suacide script for units to attack the nearest enemy, if you use the order move or attack then the computer units wont attack anything on their way to their destination, using the patrole order is what you need. remember to set a timed cycle on the order you give the units if you order em instantly preserved it will fuck up the order, so you need use a death count variable, set to 65 death count variable preserved when doin the patrole order and in another trigger you substract 1 from that death count variable preserved.

Thank you very much for the response! I understood the first half as I did have it set as :Order to Attack to destination, but I got a bit confused regarding the death count variable. I'm not too sure how to make that into a trigger. Thanks!

Theres death count function in conditions and theres set death count function in actions.

to setup a simple variable system, you need two triggers

in trigger 1

condition p1

always

action

add 1 death count to marine p1
preserved


trigger 2
condtion p1
p1 suffered 100 death count marine

action
order all men at anywhere to patrol to location destination
set death count marine set to 0 p1
preserved


p1=player1 but could be any player which is in the game either a human active player or a computer player
death count marine could be other unit buildings too(a variable) if using marine that player must never own a marine because than youre variable system can be affected if that marine is killed.
location destination is where you want your units to attack(patrole to)


with this system you can make units attack to another location fairly easy