Greetings, I am attempting to create an alien base or human base, that can't be destroy if the mission succeeds? Like you kill every one and the mission won't progress to the next level or ends. It stays this way unless you evacuate off the missionsite with your craft? I want to make cities as bases and you can raid civilians for soldiers and scientist but they will attack you back. You can't destroy the "base" because it is a city. Appreciate any input on the matter. Thank you.