The end of the Yuan was the second turning point in Mongol history. The retreat of more than 60,000 Mongols into the Mongolian heartland brought radical changes to the quasi feudalistic system. In the early fifteenth century, the Mongols split into two groups, the Oirad in the Altai region and the eastern group that later came to be known as the Khalkha in the area north of the Gobi.
A lengthy civil war (1400-54) precipitated still more changes in the old social and political institutions. By the middle of the fifteenth century, the Oirad had emerged as the predominant force, and, under the leadership of Esen Khan, they united much of Mongolia and then continued their war against China. Esen was so successful against China that, in 1449, he defeated and captured the Ming emperor. After Esen was killed in battle four years later, however, the brief resurgence of Mongolia came to an abrupt halt, and the tribes returned to their traditional disunity.
After nearly two more decades of Oirad-Khalkha conflict, another Oirad chieftain, Dayan Khan, assumed central leadership in 1466 and reunited most of Mongolia. By the end of the fifteenth century, he had restored peace and had established a new confederation comprising a vast region of North-central Asia, between the Ural Mountains and Lake Baykal. He then extended his control eastward to include the remainder of Khalkha Mongolia. The Oirad were surrounded by the Turkic descendants of the Chagadai Mongols who occupied the lowlands to the east and west, in the three independent khanates of Yarkand (modern Xinjiang south of the Tian Shan Mountains), Ferghana, and Khwarizm. Early in the sixteenth century, these three khanates were overwhelmed, however, by the Uzbeks, who earlier had broken loose from Mongol authority. The Uzbeks consolidated their control over Bukhara (Bokhara), Samarkand, Khwarizm, and Herat. During Dayan Khan's rule, quasi-feudalistic administration was reestablished, and tribes became more settled, with more specified grazing areas. What little government existed was exercised by noble descendants of Chinggis (including
Dayan), but it met with great resistance.
After the death of Dayan in 1543, the Oirad and the Khalkha disintegrated once more into insignificant and quarrelsome tribal groupings. The Torgut subclan of the Oirad was now perhaps the most vital of the Mongol peoples. The Torgut raided frequently across the Urals into the Volga Valley, which had been conquered by the new Muscovite empire. Farther east the Khalkha roamed the region north and south of the Gobi; the Ordos Mongols and the Chahar Mongols became loosely grouped in a confederation holding most of Southern Mongolia. The boundaries of territories ruled by the Uzbeks remained relatively stable.
Throughout this period of discord among the Mongols, they nonetheless shared a continuing hostility to the Ming. The struggle was maintained principally by the Khalkha. Although the title had become almost meaningless, the line of the khans had continued in the Chahar tribe, the leader of which became the rallying point for the conflict against China.
The war with China was renewed with considerable energy after Altan Khan (1507-83) of the Tumed clan united the Khalkha. Although he was not so prominent in history as his predecessor, Dayan, or his successor, Galdan Khan (1632-97), Altan was probably the greatest of the Mongol princes in the centuries following the collapse of the Yuan. By 1552 he had defeated the Oirad and had reunited most of Mongolia. It soon became obvious to Altan that there was nothing to be gained by continuing the war with the Ming; the empire of Chinggis never could be restored. Accordingly, he concluded a treaty with the Ming emperor in 1571, ending a struggle that had lasted more than three centuries.
In the remaining eleven years of his life, Altan aggressively pushed Mongol power to the south and the southwest, and he raided Tibet extensively. Altan, in turn, was coopted by a Buddhist revival in Tibet, and he became a fervent convert. In 1586 the first lamaist monastery was established in Mongolia, and Buddhism--specifically, Lamaism--became the state religion.