A Short History of the World by H.G. Wells

While the Greeks in the cities in Greece, South Italy and Asia Minor were embarking upon free intellectual enquiry and while in Babylon and Jerusalem the last of the Hebrew prophets were creating a free conscience for mankind, two adventurous Aryan peoples, the Medes and the Persians, were in possession of the civilization of the ancient world and were making a great empire, the Persian empire, which was far larger in extent than any empire the world had seen hitherto. Under Cyrus, Babylon and the rich and ancient civilization of Lydia had been added to the Persian rule; the Phoenician cities of the Levant and all the Greek cities in Asia Minor had been made tributary, Cambyses had subjected Egypt, and Darius I, the Mede, the third of the Persian rulers (521 B.C. ), found himself monarch as it seemed of all the world. His couriers rode with his decrees from the Dardanelles to the Indus and from Upper Egypt to Central Asia.

The Greeks in Europe, it is true, Italy, Carthage, Sicily and the Spanish Phoenician settlements, were not under the Persian Peace; but they treated it with respect and the only people who gave any serious trouble were the old parent hordes of Nordic people in South Russia and Central Asia, the Scythians, who raided the northern and north-eastern borders.