The origin and early history of both Medes and Persians were similar. When first the Persians are mentioned in Assyrian annals, they had migrated to the region east of Assyria, inhabiting an indefinite district which later became part of the Median state. At this time--about the ninth century before the Christian era--they were not united under one king, but each clan followed the leadership of a chosen chieftain. As a result of an Assyrian attack, more than twenty of these chiefs brought tribute and acknowledged the supremacy of the great king. Nothing of importance is again heard of them until shortly before the fall of the Assyrian capital. They were then united into a kingdom, serving one ruler, and living in what has been called "Persia Proper," to distinguish the original state from the wide empire which was brought at length under Persian rule. While free to manage their internal affairs, they paid tribute to Media, now a vigorous and aggressive nation. It is plain then, that previous to the fall of Nineveh, the Persian state had taken no part in Asiatic affairs, and furthermore, was not yet free and independent. However, in less than one hundred years her people had gained control over the entire western portion of Asia, extending their rule from the Indus to the valley of the Nile, while only the little Greek nation held out against them on the west. Before entering upon a study of this rapid imperial expansion, it would be well for us to get some general impressions of the comparatively small territory in which the various Persian tribes became welded into a united people, and of the conditions in the original kingdom wherein the principles which were to temporarily dominate the ancient world were developed. Persia Proper consisted of an area of about 450 miles in length, and averaging 250 miles in width. It might have been roughly bounded on the south and west by the gulf which came to bear its name, while a desert reached off to the east and north, save where Persian territory touched upon the Median kingdom. A narrow strip of arid land lay between the gulf and a mountain range, making up perhaps one eighth of the entire area. The climate here is hot and dry, the soil marshy, producing little growth of any sort. The district east of this range was irregularly divided into highlands and valleys, lofty rocks and winding chasms. Wherever water was available, vegetation was luxuriant, making the wild scenery fantastic and attractive. Generally water was scarce, and most of the year the land lay parched and brown.