The Mongol Empire was a steppe empire founded in 1206, when a council of Mongol tribes on the Mongolian Plateau proclaimed Temüjin as Genghis Khan, and it remains the largest contiguous land empire in history. At its peak, which the historian Rein Taagepera dates to 1309 and Peter Turchin to 1270, it covered about 24 million km² (9.3 million sq mi), roughly 18% of the world's land outside Antarctica, stretching from the Sea of Japan to the Carpathian Mountains and from Siberia to the Iranian plateau. It was ruled by Genghis Khan and his descendants, and by 1294 it had split into four khanates: the Yuan dynasty in China, the Golden Horde, the Chagatai Khanate and the Ilkhanate. It mattered because it placed most of the overland routes between China and the Mediterranean world under Mongol control, and because its conquests killed millions and redrew the political map of Asia and Eastern Europe.
Lake Baikal to the Kurultai of 1206
The Mongols first appear in the records of the late tenth century, migrating from eastern Manchuria onto the Mongolian Plateau and settling southeast of Lake Baikal near the mountain Burkhan Khaldun. For most of the twelfth century they were weaker than the Naimans and the Kerait, and competed with smaller tribes such as the Merkit and the Tatars.
Temüjin, born around 1162, rebuilt Mongol power through a mix of alliance and war. He destroyed the Tatars in 1202, overcame the Kerait khan Toghrul in 1203 and subjugated the Naimans over the next two years. At a kurultai (assembly) in 1206 he took the title Genghis Khan and ruler of the Yeke Mongghol Ulus, the "Great Mongol Nation".
What turned a tribal victory into an empire was the reorganisation that followed. Genghis broke up the old tribal structure and redistributed the steppe peoples into units on a decimal system: ninety-five minqad, or units of a thousand, each divided into hundreds and tens. He issued a law code, the Yassa, and adopted the Uyghur script for writing Mongolian. The historian Timothy May calls it a "social revolution": men from different tribes were mixed into the same units so that the old tribal loyalties would disappear.
Horses, the Eurasian Steppe and the Yam Relay
The geography of the steppe gave the Mongols their military edge. A grassland belt runs almost unbroken from Mongolia to the Hungarian plain, and an army of horse archers that fed its mounts on grass could cross it at a speed no settled state could match. A Mongol soldier took five or six horses on campaign and rode a fresh one on alternate days. The small Mongolian horse, usually unshod, could cover about 970 km (600 mi) in nine days.
They also learned siege warfare, bringing Muslim and Chinese siege engineers into their armies, and gathered intelligence from merchants and scouts before campaigns. The populations of captured cities, apart from useful craftsmen, were usually massacred.
Holding the conquests together depended on the yam, a network of relay stations. Riders usually changed horses every 40 km (25 mi) and regularly covered 200 km (125 mi) in a day. When Ögedei Khan died in Mongolia in December 1241, the news reached Batu's army in Central Europe within four to six weeks. Under Kublai Khan, the Yuan system alone had some 1,400 postal stations using 50,000 horses, 8,400 oxen, 6,700 mules, 4,000 carts and 6,000 boats.
Campaign by Campaign: Western Xia in 1209 to the Song Surrender in 1276
Expansion began close to home. After several raids, Genghis launched a full-scale invasion of the Tangut kingdom of Western Xia in 1209, and its emperor submitted as a vassal in January 1210. In 1211 he invaded the Jin dynasty. Jebe forced the Juyong Pass in 1213, the Jin court fled about 600 km south to Kaifeng, and their old capital Zhongdu (modern Beijing) fell on 1 June 1215.
The westward turn came after a trade dispute. In 1218 the governor of Otrar massacred the merchants of a Mongol-sponsored caravan and seized their goods. Otrar belonged to the Khwarazmian Empire of Central Asia and Persia. Otrar was besieged from autumn 1219 and fell in February 1220. Genghis and his son Tolui crossed the Kyzylkum Desert to take Bukhara the same month, and Samarkand fell in March. Genghis and Tolui then laid waste to Khorasan, destroying Nishapur, Merv and Herat. Even John Man's estimate of 1.25 million dead for the whole campaign describes a demographic catastrophe.
The generals Jebe and Subutai then rode about 7,500 km around the Caspian Sea, defeating a Rus' and Cuman army at the Kalka River, in today's Donetsk Oblast in Ukraine, on 31 May 1223. Genghis died in August 1227 during his final campaign against Western Xia, by which point the empire covered about 13.5 million km² by Taagepera's estimate.
His son Ögedei kept up the pace. Kaifeng fell in 1232 and the Jin dynasty ended in 1234. In 1235 Karakorum, in the Orkhon valley of central Mongolia, was walled and given a palace as the imperial capital. By 1240 Batu had taken nearly all of Kievan Rus'. In April 1241 one Mongol army beat a Polish and Moravian force at Legnica in Silesia on the 9th, and another destroyed the Hungarian army at Mohi on the Sajó River on the 11th.
Under Möngke Khan the conquests went on in the south and west. Hulagu besieged Baghdad, which surrendered on 10 February 1258; the caliph al-Musta'sim was killed along with a vast number of the city's people, and the Abbasid Caliphate came to an end. In China, the Song imperial family surrendered in 1276, and the Mongols became the first non-Chinese people to conquer the whole country.
The Peak Around 1270–1309: 24 Million km² and 31% of the World's People
Taagepera's 1997 figures put it at 24.0 million km² in 1309, while Turchin, Adams and Hall give the same area for 1270. Both put it second only to the British Empire, which reached 35.5 million km² in 1920, and ahead of the Russian Empire's 22.8 million km² in 1895.
The Oxford World History of Empire (2020) estimates that around 1290 it governed about 31% of the world's population, the largest share of them in Yuan China.
The peak in area came after political unity had already gone. By 1270 the great khan's authority was contested, and by 1309 the empire was four khanates that recognised the Yuan emperor only nominally after a peace agreed in 1304. What held the space together in those decades was the Pax Mongolica: a period of relative peace in which merchants, envoys and missionaries travelled between China, Persia and Europe on routes protected by Mongol garrisons and the yam. At the Maragheh observatory in Persia, begun with Hulagu's funding in 1259, Nasir al-Din al-Tusi worked alongside Hulagu's Chinese astronomer Fao Munji.
Where the Advance Stopped: Ain Jalut, Hakata Bay and Đại Việt
In the west, Hulagu withdrew most of his army after Möngke died in 1259, leaving about 10,000 troops west of the Euphrates under Kitbuqa. On 3 September 1260 the Mamluks of Egypt defeated them at Ain Jalut in the Jezreel Valley, and Kitbuqa was killed. Later Ilkhans briefly occupied Syria in 1299 but never pushed on toward Egypt.
In the east, the sea was the barrier. Kublai sent invasion fleets against Japan in 1274 and 1281, and both campaigns were fought along Hakata Bay near modern Fukuoka. After the first attack, the Japanese built a stone wall about 20 km long along the bay. The second invasion was thwarted by a typhoon, the origin of the word kamikaze, "divine wind". In Southeast Asia, Mongol armies invaded Đại Việt in northern Vietnam three times between 1258 and 1287 and were crushed at Bạch Đằng. The invasion of Burma was costly, the attack on Champa in southern Vietnam ended in defeat, and Temür's campaigns against the Thai and Shan states between 1297 and 1303 ended in a tributary relationship rather than conquest.
Succession Wars, the Black Death and the Ming Victory of 1368
The empire's main weakness was succession. Genghis left his realm as the joint property of his family, and every great khan's death required a kurultai of the princes. Ögedei's death in 1241 is often given as the reason the invasion of Europe was called off in 1242, though some historians stress European stone fortifications instead. When Möngke died in 1259, two rival kurultai elected his brothers Kublai and Ariq Böke, who fought the Toluid Civil War from 1260 to 1264. Kublai won, but the Berke–Hulagu war between the Golden Horde and the Ilkhanate and Kaidu's long war against Kublai followed. By Kublai's death in 1294 the four khanates were independent states. Beneath the quarrels lay a split over settled, cosmopolitan rule versus nomadic steppe life.
The khanates then fell one by one. The Ilkhanate collapsed after Abu Sa'id died in 1335 and had broken apart by 1353. The Black Death struck in the 1340s, reportedly reaching Europe when a Golden Horde army besieged the Genoese port of Caffa in Crimea in 1347. It killed up to 50 million people in Europe alone, cut trade links and devastated every khanate. In China, the Yuan court's paper money slid into hyperinflation, and the Red Turban Rebellions broke out in 1351. Ming forces took the Yuan capital Dadu in 1368, and the Mongol court fled north to the steppe.
Northern Yuan, the Great Horde and the Last Khanates
The Yuan rulers who retreated to Mongolia became the Northern Yuan, a rump state that lasted until the Qing conquest in the 1630s. The Golden Horde lost its western lands to Poland and Lithuania between 1342 and 1369, and later split into rival khanates. Its rule over the Russian principalities traditionally ends in 1480, when Ivan III of Moscow stopped paying tribute and faced down Akhmat Khan of the Great Horde at the Great Stand on the Ugra River. The Chagatai Khanate split in two in the mid-fourteenth century and lost Transoxiana to Timur from the 1360s, but its last offshoot, the Yarkent Khanate, survived until the Dzungar conquest of 1705.
The human cost of the conquests was enormous. The death toll is commonly cited as 40 to 60 million, a figure from McEvedy and Jones's 1978 Atlas of World Population History whose sources later scholars have questioned. Against that stands the Pax Mongolica's legacy of trade and contact, much of it carried along the routes described in our guide to the geography of the Silk Road. To see the grassland corridor that made the conquests possible, read about the geography of the Eurasian Steppe and the Gobi Desert, or compare the empire's size with the one that surpassed it in our British Empire geography guide.