I think that, especially in our current days where we have to get used to the idea of war again, it's really important to look back. As a german I can say, that war never was good for our country. We only lost land, cities, history and most importantly lives.
I think, that there should be one rule: The people responsible for the war, should be at the frontline. Then, there would never be a war again.
Also, it's important to appreciate peace, as long as we still have it.