What is War?

Is it a creative course of action used to settle differences between nations, or is it just a way for nations to take out all their anger felt towards each other? I personally think it is a foolish action done when nations are unable to deal with a problem in a civilized manner. There are wars that have been going on for decades and because the different societies have grown to despise one another, these people are unable to have a discussion without another war beginning. If these different nations respected one another, than military would know better than to kill innocent people because of something foolish done by their leader/s.