Between 1206 and 1368, an obscure group of Central Asian nomads exploded across the steppes and established the world's largest contiguous empire in history - the Mongol Empire. Led by their "oceanic leader," Genghis Khan (Chinggus Khan), the Mongols took control of approximately 24,000,000 square kilometers (9,300,000 square miles) of Eurasia from the backs of their sturdy little horses.
Before a 1206 kuriltai in what is now Mongolia appointed him as their universal leader, the local ruler Temujin simply wanted to ensure the survival of his own little clan in the dangerous internecine fighting that characterized the Mongolian plains in this period. However, his charisma and innovations in law and organization gave Genghis Khan the tools to expand his empire exponentially. He soon moved against the neighboring Jurchen and Tangut peoples of northern China, but seems not to have had any intention of conquering the world until 1218, when the Shah of Khwarezm confiscated a Mongol delegation's trade goods and executed the Mongol ambassadors.
Furious at this insult from the ruler of what is now Iran, Turkmenistan and Uzbekistan, the Mongol hordes sped westward, sweeping aside all opposition. The Mongols traditionally fought running battles from horseback, but they had learned techniques for besieging walled cities during their raids of northern China. Those skills stood them in good stead across Central Asia and into the Middle East; cities that threw open their gates were spared, but the Mongols would kill the majority of citizens in any city that refused to yield and open its gates.
Under Genghis Khan, the Mongol Empire grew to encompass Central Asia, parts of the Middle East, and east to the borders of the Korean Peninsula. The heartlands of India and China held off the Mongols for the time, however, as did Korea's Goryeo Kingdom. In 1227, Genghis Khan died, leaving his empire divided into four khanates that would be ruled by his sons and grandsons. These were the Khanate of the Golden Horde, in Russia and Eastern Europe; the Ilkhanate in the Middle East; the Chagatai Khanate in Central Asia; and the Khanate of the Great Khan in Mongolia, China and East Asia.
In 1229, the kuriltai elected Genghis Khan's third son Ogedei as his successor. The new great khan continued to expand the Mongol empire in every direction, and also established a new capital city at Karakorum, Mongolia. In East Asia, the northern Chinese Jin Dynasty, which was ethnically Jurchen, fell in 1234; the southern Song Dynasty survived, however. Ogedei's hordes moved into Eastern Europe, conquering the city-states and principalities of Rus (now in Russia, Ukraine and Belarus), including the major city of Kiev. Further south, the Mongols took Persia, Georgia and Armenia by 1240, as well.
In 1241, Ogedei Khan died, bringing to a temporary halt the Mongols' momentum in their conquests of Europe and the Middle East. Batu Khan's ordu was preparing to attack Vienna when news of Ogedei's death distracted the leader. Most of the Mongol nobility lined up behind Guyuk Khan, the son of Ogedei, but his uncle Batu Khan of the Golden Horde refused the summons to the kuriltai. For more than four years, the great Mongol Empire was without a great khan.
Finally, in 1246, Batu Khan agreed to the election of Guyuk Khan, in an effort to hold off an impending civil war. Guyuk Khan's official selection meant that the Mongol war machine could once more grind into operation. Some previously-conquered peoples took the opportunity to break free from Mongol control, however, while the empire was rudderless. The Assassins or Hashashshin of Persia, for example, refused to recognize Guyuk Khan as the ruler of their lands.
Just two years later, in 1248, Guyuk Khan died either of alcoholism or poisoning, depending upon which source one believes. Once again, the imperial family had to choose a successor from amongst all the sons and grandsons of Genghis Khan, and make a consensus across their sprawling empire. It took time, but a 1251 kuriltai officially elected Mongke Khan, grandson of Genghis and son of Tolui, as the new great khan.
More of a bureaucrat than some of his predecessors, Mongke Khan purged many of his cousins and their supporters from the government in order to consolidate his own power, and reformed the tax system. He also carried out an empire-wide census between 1252 and 1258. Under Mongke, however, the Mongols continued their expansion in the Middle East, as well as attempting to conquer the Song Chinese.
Mongke Khan died in 1259 while campaigning against the Song, and once more the Mongol Empire needed a new head. While the imperial family debated the succession, Hulagu Khan's troops, which had crushed the Assassins and sacked the Muslim Caliph's capital at Baghdad, met with defeat at the hands of the Egyptian Mamluks in the Battle of Ayn Jalut. The Mongols would never restart their expansionary drive in the west, though East Asia was a different matter.
This time, the Mongol Empire descended into a civil war before another of Genghis Khan's grandsons, Kublai Khan, managed to take power. He defeated his cousin Ariqboqe in 1264 after a hard-fought war, and took the reins of empire. In 1271, the great khan named himself the founder of the Yuan Dynasty in China, and moved in earnest to finally conquer the Song Dynasty. The last Song emperor surrendered in 1276, marking the Mongol victory over all of China. Korea also was forced to pay tribute to the Yuan, after further battles and diplomatic strong-arming.
Kublai Khan left the western portion of his realm to the rule of his relatives, concentrating on expansion in East Asia. He forced Burma, Annam (northern Vietnam), Champa (southern Vietnam) and the Sakhalin Peninsula into tributary relationships with Yuan China. However, his expensive invasions of Japan (1274 and 1281) and of Java, Indonesia, in 1293 were complete fiascos.
Kublai Khan died in 1294, and the Yuan Empire passed without a kuriltai to Temur Khan, Kublai's grandson. This was a sure sign that the Mongols were becoming more Sinofied. In the Ilkhanate, the new Mongol leader Ghazan converted to Islam. A war broke out between the Chagatai Khanate of Central Asia and the Ilkhanate, which was supported by the Yuan. The ruler of the Golden Horde, Ozbeg, also a Muslim, restarted the Mongol civil wars in 1312; by the 1330s, the Mongol Empire was coming apart at the seams.
In 1335, the Mongols lost control of Persia. The Black Death swept across Central Asia along Mongol trade routes, wiping out entire cities. Goryeo Korea threw off the Mongols in the 1350s. By 1369, the Golden Horde had lost Belarus and Ukraine in the west; meanwhile the Chagatai Khanate disintegrated and local warlords stepped in to fill the void. Most significant of all, in 1368, the Yuan Dynasty lost power in China, overthrown by the ethnic-Han Chinese Ming Dynasty.
Genghis Khan's descendants continued to rule in Mongolia itself until 1635, when they were defeated by the Manchus. However, their great realm, the world's largest contiguous land empire, fell apart in the fourteenth century after less than 150 years in existence.