I've been faced with the decision a few times of sacrificing a soldier to make sure I can save a 6th civilian before they all die, and I'm wondering how to weight the pros and cons of that trade. I haven't failed a retaliation mission yet and am wondering what detrimental effects it has.
When you fail to save enough civvies, you lose contact with the resistance in that area, and will have to reestablish contact by scanning the area again. While contact is lost, your radio tower in the area will not be available. Even after contact is reestablished, you suffer a penalty to the amount of supplies they provide per month.