In the movie Deathly Hallows - Part 2, we see Harry use the Imperius curse (The Imperius Curse is one of the three Unforgivable Curses, when cast successfully, it places the victim completely under the caster's control).
Being an unforgivable curse, why was Harry not sent to Azkaban after Hogwarts Battle end?
EDIT: The answers are quite right, but I'm still not satisfied. The point of the question is: if an unforgivable curse is a crime, doing it during a war is a War Crime, and a "good" system should convict its own side war criminals as well. Why did this not happen?