Turks, one of the most important branches of the Turanian family. (See Turanian Race and Languages, and Turkish Language and Literature.) In former ethnological classifications they were sometimes set down as a Caucasian race, and in physical characteristics some of their tribes are nearly or quite Caucasian; but more recent science shows that they have no connection with the Aryan or Indo-European family. They made their first appearance in northern and central Asia among the Hunnic and Tartaric hordes who for several centuries before and after our era were the terror of the Chinese. (See China, vol. iv., p. 459, Huns, and Tartars.) Turk is used in central Asia as synonymous with Tartar, or to designate the Mongolians generally. Before the commencement of the Christian era a tribe of Turks had wandered westward as far as the Don; they are mentioned by Pliny under the name of Turcee, and by Pomponius Mela under that of Iurcae; while other tribes had not long after penetrated into the mountainous regions of Asia Minor. In the 4th and 5th centuries of the Christian era a portion of the Turks who had remained in N. W. China conquered two provinces of that country, which they organized as independent kingdoms, to which the Chinese give the names of Chao and Northern Liang; but the greater part of those who were driven out in the 3d century rallied around Lake Balkash, and after the 5th century made no further separate appearance in history.

In the early part of the 6th century a new Turkish empire, apparently having its nucleus in what is now East Turkistan, threatened the peace of Asia. These Turks renewed their conflicts with China at the east, and with Persia at the southwest, and in 569 formed an alliance with Justin II., then emperor of Constantinople, for the overthrow of the Sassanides. But this Turkish empire (which the Chinese called Tu-kiu), like all the attempts of the Turks at imperial domination, was an agglomeration of dissimilar peoples in one huge nation, with no common bond of union or citizenship, and its very vastness contributed to its weakness. In the empire was overthrown by the attacks of the Hoei-he or Hoei-hu, as the Chinese named them (the Uigurs of western writers), another Turkish tribe who had previously been subjects of the Tu-kiu empire. There were at this time, and had been for some centuries, eight distinct Turkish tribes or nations in central Asia. The Uigurs never attained to the vast power of their predecessors, but they were the first of the Turkish tribes to adopt a written language.

At first they were Buddhists; but about the 4th century they became very generally disciples of Zoroaster, and in the 9th or 10th century embraced Islamism. In the west their empire was overthrown in 848 by the Kirghiz Tartars; but they maintained an independent kingdom in the valleys of the Thian-shan range till about A. D. 1000, when the increasing power of the Khitans in China compelled their emigration westward. The invasion of Genghis Khan overthrew the last remains of the Turkish empire in central Asia; but the prominent officers of that conqueror and his successors were taken from this very tribe of Uigurs on account of their superior intelligence. But meanwhile the Turks had been acquiring new territories in the west. In the 6th and 7th centuries they were already in possession of an extensive region in what is now Asiatic Turkey, and were pressing forward toward S. E. Europe. In the 9th and 10th centuries the Tulunides and Ikshides, who founded short-lived dynasties in Egypt before the Fatimites, were Turks. In the 9th century a Turkish dynasty, the Taherides, ruled in Khorasan; and their successors, the Ghuznevides and the Ghorides, extended their sway from Persia to India between the 10th and 12th centuries.

But a more famous Turkish dynasty than either of these was that of the Seljuks, whose dominion extended in the latter part of the 11th century from the frontiers of China to the vicinity of Constantinople. (See Seljuks.) Like its predecessors, this vast empire crumbled to pieces from its want of homogeneity, and the Seljukian sultans submitted,.to be tributaries of the Mongol emperors. About the beginning of the 14th century the Ottoman empire was founded by Othman, a Turkish chief, and in the succeeding centuries spread over a vast territory in Asia and Europe. (See Turkey.) The Turkish tribes which had submitted to the Mongol invasion in the 13th century, and still remained in the region of the Thian-shan mountains, the Aral, and the Caspian, sent out colonies N. of the Caspian into that portion of southern Russia lying on the borders of the Black sea, where, under the name of Tartars, several tribes of them still occupy extensive territories. While acknowledging the Russian sway, they are still zealous Mohammedans. The Mongol invaders of Turkistan, instead of impressing their own habits and language upon the Turks of that country, gradually became identified with the people they had conquered; and eventually, the Turkish element again predominating, in the age following the death of Tamerlane they had invaded and subdued Armenia and the countries bordering on the Tigris and Euphrates. From this region they were expelled in the 16th century by the Sufis. In the same century the Uzbecks, a Turkish tribe, primarily inhabiting the southern provinces of Chinese Turkistan below the Thian-shan mountains, and said to be descendants of the Uigurs and the Naimans, made their way westward, and overran not only East Turkistan but the countries adjacent as far as the Euphrates, and were, after maintaining their power for more than a century, reduced to subjection by still another Turkish tribe, the Turkomans. The Turkomans and Uzbecks are now, in the ancient seat of the Turks, the principal remaining tribes of that powerful race.

The Calmucks between the lower Volga and Don, the Bashkirs between the Volga and Irtish, and the Yakuts on the banks of the Lena, are also Turkish tribes. The Yakuts are the only Turkish race professing Shamanism.