What we know for certain is that civilization is well advanced. Both in the north and the south there are many organized and independent city states, and not unfrequently these wage war one against another. Occasionally ambitious rulers tower among their fellows, conduct vigorous military campaigns, and become overlords of wide districts. As a rule, a subjugated monarch who has perforce to acknowledge the suzerainty of a powerful king is allowed to remain in a state of semi-independence on condition that he pays a heavy annual tribute of grain. His own laws continue in force, and the city deities remain supreme, although recognition may also be given to the deities of his conqueror. He styles himself a Patesi--a "priest king", or more literally, "servant of the chief deity". But as an independent monarch may also be a pious Patesi, it does not always follow when a ruler is referred to by that title he is necessarily less powerful than his neighbours. When the historical narrative begins Akkad included the cities of Babylon, Cutha, Kish, Akkad, and Sippar, and north of Babylonia proper is Semitic Opis. Among the cities of Sumer were Eridu, Ur, Lagash, Larsa, Erech, Shuruppak, and probably Nippur, which was situated on the "border". On the north Assyria was yet "in the making", and shrouded in obscurity. A vague but vast area above Hit on the Euphrates, and extending to the Syrian coast, was known as the "land of the Amorites". The fish-shaped Babylonian valley lying between the rivers, where walled towns were surrounded by green fields and numerous canals flashed in the sunshine, was bounded on the west by the bleak wastes of the Arabian desert, where during the dry season "the rocks branded the body" and occasional sandstorms swept in blinding folds towards the "plain of Shinar" (Sumer) like demon hosts who sought to destroy the world. To the east the skyline was fretted by the Persian Highlands, and amidst the southern mountains dwelt the fierce Elamites, the hereditary enemies of the Sumerians, although a people apparently of the same origin. Like the Nubians and the Libyans, who kept watchful eyes on Egypt, the Elamites seemed ever to be hovering on the eastern frontier of Sumeria, longing for an opportunity to raid and plunder.