 King Croesus of Lydia established an alliance with the Spartans, and later, the Greek cities of Asia Minor appealed to them for help during the Ionian Revolt.In the second Persian invasion of Greece, under Xerxes, Sparta was assigned the overall leadership of Greek forces on land and at sea.The Spartans played a crucial role in the repulsion of the invasion, notably at the battles of Thermopylae and Plataea.