"What is it good for? Absolutely nothing!"
This shouted refrain is the chorus of Edwin Starr's 1969 classic, "War." Despite the opinion of Starr and hundreds of other celebrities over the decades, war remains a central theme of human history. According to reporting from The New York Times, humans have been fully at peace for only 268 out of the last 3,400 years.
This means that for 92% of recorded history, civilizations have been fighting each other. Wars start for many reasons, but religion and territory have undoubtedly been the two most significant. Consider World War II, a conflict borne largely from Adolf Hitler's insatiable desire to spread his Nazi empire across all of Europe. Thousands of years before Germany came under Hitler's reign, a series of Persian kings waged a campaign with a similar goal. At its height, Persia controlled nearly 3 million square miles across Africa, Europe and Asia.
Whether it's an ancient conflict for land or a modern battle over ideology, one constant of war is the human cost. By some estimates, nearly a billion people have lost their lives throughout human history thanks to violent conflict. Historians tend to compare battles and rank them based on which were deadliest, a grim sorting for bloody conflicts of history.
How much do you know about the cost of war? Take this quiz to find out.