Athens and Sparta were two very different city-states in ancient Greece. Their differences sometimes led to a distrust of each other. But between 499 and 479 B.C.E., these city-states had a common enemy—the Persian Empire. At that time, Persia was the largest empire the world had ever seen. Its powerful kings ruled over lands in Africa, the Middle East, and Asia. During the 400s B.C.E., the Persians invaded Greece, and the Persian wars began. To fight the Persians, the Greek city-states eventually joined together as allies. Allies are states that agree to help each other against a common enemy. Compared with Persia, these tiny Greek city-states had much less land and far fewer people. How could they possibly turn back such a powerful invader? In this chapter, you will learn about important battles during the Persian wars and discover who won them. You will also learn about the factors that influenced the outcome of the Persian wars. 28.2 – The Persian Empire and the Ionian Revolt