Mission Battles during the story-line have three possible outcomes Mission Complete, Mission Clear, and Mission Failed.
If you complete the minimum conditions to win you'll get a Mission Clear, if you complete more than the minimum you'll get a Mission Complete obtaining more EXP, KP, and Mil. Mission Failed is self-explanatory.
Victory Condition: At least 3 civilians survived
Defeat Condition: Failed to save at least 3 civilians
Mission Complete Condition: All civilians survived
Mission Clear Condition: At least 3 civilians survived
Mission Failed Condition: Failed to save at least 3 civilians