Genghis Khan (c. 1167–1227) had four sons by his principal wife, Borte. The eldest son, Juji, and second son, Chagatai, were such fierce rivals that Genghis decided to bypass both in favor of his third son, Ogotai Khan as his successor khaghan (Grand Khan), and all of his sons agreed with his choice.
Genghis also assigned territories to each son to govern, although all would acknowledge the leadership of the khaghan and cooperate with him in expanding the Mongol Empire. Juji received land farthest from the paternal homeland—the western territories that would include Russia and eastern Europe; his followers were called the Golden Horde.
Chagatai received west Turkestan, the Tarim Basin, and the western Tian Shan (T’ien Shan) region. Ogotai received Dzungaria and part of Central Asia, while the youngest son, Tului, received the Mongolian homeland. This arrangement was confirmed just before Genghis Khan died in 1227. Two years later the Kuriltai (council of nobles) elected Ogotai the next khaghan.
Chagatai’s allotment, which was enlarged later, also included the Ili River valley, Kashgaria, Turfan and Kucha in present-day northwestern China, and Transoxiana, including the towns of Samarkand. These disparate lands became known as the Chagatai Khanate. Except for the oasis towns most of the khanate was steppe land inhabited by various nomads, most of Turkic ethnicity.
Chagatai was a warrior and also a staunch upholder of Mongol traditions. Genghis had appointed him guardian of the Mongolian law code called “Yasa” which he had sternly administered. Chagatai and his successors kept up a seminomadic lifestyle, changing from winter to summer camp as the seasons dictated.
Whereas the Mongol realms under Kubilai Khan and his heirs in China, the Yuan dynasty (1279–1368), and the il-khanate of Hulagu Khan and his successors in Persia and the Middle East had fixed boundaries, rich resources, large sedentary populations, and long established traditions of governance, the Chagatai Khanate had shifting boundaries, tribal populations with weak state institutions, and relatively sparse resources.
It was hemmed in by other Mongol dominions ruled by branches of Genghis Khan’s descendants in three directions—the Yuan dynasty, the Il-Khanate, and the Golden Horde in Russia. The only direction for expansion was into Afghanistan and India. Beginning in the 1290s Chagatai Khanate forces took control of eastern Afghanistan from which they raided northwestern India.
In 1303 an expedition of 120,000 men besieged Delhi for two months and devastated a wide area. Another force of 40,000 horsemen returned to India in 1304 but was defeated and 9,000 prisoners were trampled to death by elephants. A similar fate befell the men of the last attacking army in 1305–1306.
Not able to expand outward the heirs of Chagatai were constantly embroiled in wars and rivalries of the other three branches of the family, and among themselves. Although the Chagatai Khanate was poor in resources, its central location along the Silk Road allowed it to collect abundant taxes and tolls. Frequent wars and predatory policy toward trade and sedentary people often resulted in the breakdown and ultimately decline in international trade by land routes.
Major differences and incompatibilities divided the eastern and western halves of the khanate. The western part, originally part of the Khwarazm kingdom, was Islamized, urbanized, and more advanced than the eastern region, which was more pastoral, nomadic, and animistic. Lacking a cohesive government, each went its own way.
Chagatai died in 1242 and was succeeded by his grandson Kara Hulagu. Interference by the khaghan and involvement by the Chagatai Khanid rulers in the dynastic struggle of other branches of the family resulted in many upheavals.
Leaders of the Chagatai Khanate became involved when Mongke Khaghan died in 1259 and a succession struggle erupted between his brothers Kubilai and Arik Boke; they sided with the winner Kubilai. Later they supported Kaidu Khan, a grandson of Ogotai, who challenged Kubilai for the throne of the khaghan. The destructive wars continued until Kaidu’s death in 1301.
Although Kubilai won against his rivals, the unity of the Mongol Empire was fractured forever, and even though the Chagatai rulers were not in contention for overall leadership, their central position in the line of communications between the different branches of the family played a significant role in the breakdown of unity of the Mongol Empire.
The frequent civil wars and changes of rulers (there were 30 khan up to 1230) fatally weakened the central authority at the expense of local leaders. As the Chagatai Khanate was disintegrating in 1369, there rose in Samarkand a Mongol-Turkic leader who claimed descent from Genghis Khan.
His name was Timurlane (Tamerlane), meaning Timur the Lame. His military career that ended with his death in 1403 would replicate that of his famous ancestor. In the 14th century Chagatain rulers converted to Islam, the religion of many of the Turkic peoples they ruled. The official language of the khanate was changed from Mongolian to Chagatai Turkic. It continued to be used in the region they ruled until modern times.