LOL, you can't just abandon your ideals during wartime, genocide the crap out of your enemy, and then return to your “ideals“ like nothing happened.
There are example of that (not genocide) happening. During the American civil war the President "turned off" the writ of habeas corpus, an important legal protection. Following the war it was switched back on.
When wartime escalates into fighting for survival, a different rule book comes off the shelf.