=9. Rise of commerce in the Mesopotamian Valley.=—The district northwest of the Persian Gulf, centering in the river valleys of the Tigris and Euphrates, offered opportunities for the rise of civilization which led to the establishment of settled governments while Egypt was still living secluded from the rest of the world. This district was rich in agricultural products, but lacked the metals, some of the building materials, and other of the raw materials of industry. Though it was bordered in part by deserts, communication with other districts was far easier than in the case of Egypt; and commerce with other countries early acquired an importance here which Egyptian commerce attained only in the last period of the country’s history. Ancient Babylon, which rose to importance some time after 3000 B.C., under a Semitic people (with a language akin to that of the Jews), was a market-place for wares brought not only from the South (Arabia) and West (Syria), but also from the East (Iran, the later Persia). Clay tablets, used like modern paper for the preservation of records, have been discovered and deciphered in modern times, and show an active trade in the precious metals, grain, wool, building materials, etc. =10. Development of commerce under the Assyrian and Persian empires.=—Military expeditions extended the commercial relations of the people of this district; and the conquests of an Assyrian, who founded a great empire about 745 B.C., were guided in part by commercial considerations. Babylon, Armenia, Syria, and parts of Iran and Palestine, were brought under one rule; peoples on the frontiers were held in check, and order was fairly well maintained within; so that merchants could traverse the different parts of the empire, and meet at its capital, Nineveh, to exchange their wares. The Assyrian empire was made by the sword, and it fell by the sword after a brief duration; but its place was taken by succeeding states, and commerce continued to grow. The Persian empire, which enjoyed its full power for about two hundred years, until its destruction by Alexander in 330 B.C., included an area more than half that of modern Europe; it stretched from the Mediterranean on the West to the Indus on the East, from the Indian Ocean and the Persian Gulf to the Black and Caspian seas. Within these boundaries lay some of the richest regions of the ancient world, the products of which could now be exchanged without passing from under the protection of the Great King.