The millennium between 500 B.C.E. and 500 C.E. in North Africa and Eurasia witnessed the flowering of second-wave civilizations in the Mediterranean world, the Middle East, India, and China. For the most part, these distant civilizations did not directly encounter one another, as each established its own political system, cultural values, and ways of organizing society. A great exception to that rule lay in the Mediterranean world and in the Middle East, where the emerging Persian Empire and Greek civilization, physically adjacent to each other, experienced a centuries-long interaction and clash. It was one of the most consequential cultural encounters of the ancient world. (For another example of contact among second-wave empires, see Zooming In: The Kushan Empire.)