This Mongol destroyer set in motion the conquest of a quarter of the world's population with a body count in the millions. Genghis Khan (/ˈɡɛŋɡɪs ˈkɑːn/ or /ˈdʒɛŋɡɪs ˈkɑːn/, Mongol: [tʃiŋɡɪs xaːŋ]; Chingis/Chinghis Khan; 1162? -- August 1227), born Temujin, was the founder and Great Khan (emperor) of the Mongol Empire, which became the largest contiguous empire in history after his demise. He came to power by uniting many of the nomadic tribes of northeast Asia. After founding the Mongol Empire and being proclaimed "Genghis Khan," he started the Mongol invasions that resulted in the conquest of most of Eurasia. These included raids or invasions of the Kara-Khitan Khanate, Caucasus, Khwarezmid Empire, Western Xia and Jin dynasties. These campaigns were often accompanied by wholesale massacres of the civilian populations -- especially in the Khwarezmian controlled lands. By the end of his life, the Mongol Empire occupied a substantial portion of Central Asia and China. Before Genghis Khan died, he assigned Ögedei Khan as his successor and split his empire into khanates among his sons and grandsons. He died in 1227 after defeating the Western Xia. He was buried in an unmarked grave somewhere in Mongolia at an unknown location. His descendants went on to stretch the Mongol Empire across most of Eurasia by conquering or creating vassal states out of all of modern-day China, Korea, the Caucasus, Central Asian countries, and substantial portions of modern Eastern Europe, Russia and the Middle East. Many of these invasions repeated the earlier large-scale slaughters of local populations. As a result Genghis Khan and his empire have a fearsome reputation in local histories. Beyond his military accomplishments, Genghis Khan also advanced the Mongol Empire in other ways. He decreed the adoption of the Uyghur script as the Mongol Empire's writing system. He also promoted religious tolerance in the Mongol Empire, and created a unified empire from the nomadic tribes of northeast Asia. Present-day Mongolians regard him as the founding father of Mongolia. The Central Asian plateau (north of China) around the time of Temüjin (the early 13th century) was divided into several tribes or confederations, among them Naimans, Merkits, Tatars, Khamag Mongols, and Keraits, that were all prominent in their own right and often unfriendly toward each other as evidenced by random raids, revenge attacks, and plundering. Temujin began his slow ascent to power by offering himself as an ally (or, according to others sources, a vassal) to his father's anda (sworn brother or blood brother) Toghrul, who was Khan of the Kerait, and is better known by the Chinese title "Wang Khan", which the Jin Empire granted him in 1197. This relationship was first reinforced when Börte was captured by the Merkits; it was Toghrul to whom Temujin turned for support. In response, Toghrul offered his vassal 20,000 of his Kerait warriors and suggested that he also involve his childhood friend Jamukha, who had himself become Khan (ruler) of his own tribe, the Jadaran. Although the campaign was successful and led to the recapture of Börte and utter defeat of the Merkits, it also paved the way for the split between the childhood friends, Temujin and Jamukha. Temujin had become blood brother (anda) with Jamukha earlier, and they had vowed to remain eternally faithful.

• published: 16 Jan 2014
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