These men of the North came from the grasslands of Russia in successive waves and among the first of whom we have fairly clear knowledge were the Achæans and Phrygians. Aryan names are mentioned in the dim chronicles of the Mesopotamian empires about 1700 B. C. among the Kassites and later, Mitanni. Aryan names of prisoners captured beyond the mountains in the north and of Aryan deities before whom oaths were taken are recorded about 1400 B. C. but one of the first definite accounts of Nordics south of the Caucasus describes the presence of Nordic Persians at Lake Urmia about 900 B. C. There were many incursions from that time on, the Cimmerians raiding across the Caucasus as early as 650 B. C. and shortly afterward overrunning all Asia Minor. The easterly extension of the Russian steppes or Kiptchak north of the Caspian-Aral Sea in Turkestan as far as the foothills of the Pamirs was occupied by the Sacæ or Massagetæ, who were also Nordics and akin to the Cimmerians and Persians, as were, perhaps, the Ephtalites or White Huns in Sogdiana north of Persia, destroyed by the Turks in the sixth century. For several centuries groups of Nordics drifted as nomad shepherds across the Caucasus into the empire of the Medes, introducing little by little the Aryan tongue which later developed into Old Persian. By 550 B. C. these Persians had become sufficiently numerous to overthrow their rulers and under the leadership of the great Cyrus they organized the Persian Empire, one of the most enduring of Oriental states. The base of the population of the Persian Empire rested on the round skulled Medes who belonged to the Armenoid subdivision of the Alpines. Under the leadership of their priestly caste of Magi these Medes rebelled again and again against their Nordic masters before the two peoples became fused. From 525 to 485 B. C. during the reign of Darius, whose sculptured portraits show a man of pure Nordic type, the tall, blond Persians had become almost exclusively a class of great ruling nobles and had forgotten the simplicity of their shepherd ancestors. Their language belonged to the Eastern or Iranian division of Aryan speech and was known as Old Persian, which continued to be spoken until the fourth century before the Christian era. From it were derived Pehlevi, or Parthian as well as modern Persian. The great book of the old Persians, the Avesta, which was written in Zendic, also an Iranian language, does not go back to the reign of Darius and was remodelled after the Christian era, but the Old Persian of Darius was closely related to the Zendic of Bactria and to the Sanskrit of Hindustan. From Zendic, also called Medic, are derived Ghalcha, Balochi, Kurdish and other dialects.