Why war or conflicts are fought between civilizations is a subject that could be debated with no end. The complexity of how our species reacts with each other and generates conflict exceeds the limitations of a single concept. There is not one answer to the question, but often the combination of the need for economic and political authority along with the thrill of victory, power, and nationalism joining together to create the motivation to fight and conquer.
"Conflicts among Civilizations: The Influence behind War and Art,"
Reason and Respect: Vol. 4
, Article 8.
Available at: http://docs.rwu.edu/rr/vol4/iss1/8