War is the continuation of diplomacy, through other means... some dude with a freaky name said that. I keep on forgetting his name... it appeared in a book, about international affairs.

Yes, war is a part of human nature - just like conflict and violence are. War serves the purpose of leaders, or of the people. It can be waged for a good cause, or for foul evil causes. I don't think it should be avoided at all costs - impotence is just as bad, and can ultimately lead to terrible things (WWII, anyone?). However, since war is usually very costly - money, lives, and values - it should not be waged over every single affair.

As for today's leaders - I don't think they should take active part in wars. This isn't ancient times, when a king used to march into battle along with his men. It simply cannot work with the social and political physics of the modern world.

War is justified whenever someone says it is. Hopefully, most sane leaders avoid it as much as possible - but war is started by the least... diplomatic side of any party.