Why do countries engage in war?

I understand the occasional war is fought for a righteous reason. To protect Your country or whatever. But let's be honest, most wars are started because of petty quarrels between powerful men. And the only reason it becomes important, is because good men die for these selfish desires. So tell me why do we do it? Are we just that ignorant, to where we actually think it's nessicary? Or are we violent creatures that get off on blood and destruction? And get high off of our own power? You tell me. Why do these humans engage in such foolish acts? And then use fancy words to justify their actions. When in reality it was nothing but power hungry, blood thirsty fools, who happened to be in control of an army.