On the Origins of War Author:Donald Kagan Kagan, professor of history and classics at Yale, analyzes the whole of history to find out why there are wars, whether there are underlying laws that explain why one nation challenges another, and whether there are underlying laws for the preservation of peace. — He analyzes five wars, ranging across 2500 years and involving widely different kin... more »ds of governments. He begins with the Greek city-states that fought the Peloponnesian Wars and moves to the Second Punic War between Rome and Carthage, before jumping to the 20th century for the two world wars and the near-war of the Cuban missile crisis. The wide temporal gap between the ancient and the modern examples highlights Kagan's thesis that peace does not keep itself: "A persistent and repeated error through the ages has been the failure to understand that the preservation of peace requires active effort, planning, the expenditure of resources, and sacrifice, just as war does."« less