Yes or no alert bar.
Find way to keep alert bar at zero so KPA won't attack us at all.
i played awhile and never so any 'alert bar'.. is there a mission where you must sneak past the KPA or something?
It is similar to heat bar in Just Cause - it will get high after spotted by KPA or shot KPA that lead to endless fighting.
I confirmed that some missions require you to be stealth or mission will be fail.