It became a practical issue because neither state could afford to keep spending on the arms race as they had been and, as we saw last week, the difficulties the Soviets were getting into with their domestic economy and domestic politics encouraged the final breakdown of the cold war and the iron curtain. Another cause of war is human nature. Human beings are seen to be like other animals with inherited aggressive instincts, supposed to be the product of evolution, of survival. Another view that humans are attracted to violence as an end in itself. There are a lot of them and they do well at the box office.
Humans also fight over property.
Hobbes - if any two men desire the same thing, which nevertheless they cannot both enjoy, they become enemies. And in the way to their end, endeavour to destroy or subdue one another. Hatred is another cause of conflict. We seek revenge against those who have done us some harm. Many wars have been holy wars - so religion can be a cause of war.