Darius was long occupied with internal disturbances. Revolts were put down with severity. When the government of the empire was firmly established, it was superior to any before known in Asia. The whole empire was divided into satrapies, or provinces--each under a resident governor; these governors made frequent reports to the capital and the opportunity for revolts was slight. Internal concerns thus settled, Darius turned to conquest. He conducted a campaign in the east, pushing Persia's possessions to the banks of the Indus. It was natural that the king should have cast longing eyes westward, toward the beautiful isles and states of Greece. Long before the age of Cyrus, Greek colonists had settled in Asia Minor. They had fallen to the share of Persia when Lydia was conquered, and Darius had organized their local government so completely that the freedom-loving Greeks were oppressed by it and in 500 B.C. revolted. These Greek cities appealed to Athens for aid in their struggle for liberty. A few soldiers were sent, and with such aid they displaced the Persian government and destroyed Sardis. Darius sent an army to put down the revolt, and the city which had led the struggle was destroyed. The king of Persia now determined to punish Athens for having given help to the revolting Greek cities of Asia Minor. Accordingly, he fitted out an expedition to conquer Greece. The naval forces were wrecked in a storm and the land forces were routed by hostile tribes en route. A second expedition was prepared, more numerous and better equipped than the first. Before dispatching it, however, Darius sent heralds to the various Greek states to inquire if they would submit peacefully. They replied with great scorn. In 490 B.C. the Persian king sent 300,000 soldiers to conquer Greece. The battle of Marathon was fought, and owing to the skill of Miltiades, the Greeks won. Four years later Darius died and Xerxes ruled in his stead. To him was left the duty of wiping out the inglorious defeat of the Persian arms. Not until 480 B.C. were the armies ready for what was expected to be a great conquest.