The Scythian and Samaritan hordes of the steppe-country between the Wolga and the Dnieper were to the monarchies of Western Asia a permanent, if a somewhat distant, peril.

It could not be forgotten that they had proved themselves capable of penetrating the rocky barrier which would otherwise have seemed so sure a protection, or that when they swarmed across it in the seventh century before our era, their strength was at first irresistible.

The Persians knew, what the great nations of the earth afterwards forgot, that along the northern horizon there lay a black cloud, which might at any time burst, carrying desolation to their homes and bringing ruin upon their civilization.

We shall find the course of their history importantly affected by a sense of this danger, and we shall have reason to admire the wisdom of their measures of precaution against it.
It was not only to the west of the Caspian that the danger threatened.
East of that sea also was a vast steppe-region--rolling plains of sand or grass--the home of nomadic hordes similar in character to those who drank the waters of the Don and Wolga.

The Sacse, Massagetse, and Dahse of this country, who dwelt about the Caspian, the Aral, and the Lower Jaxartes, were an enemy scarcely less formidable than the Sarmatians and the Scyths of the West.