From clans to a steppe state
In the late twelfth century the grasslands of what is now Mongolia were home to many rival tribes and confederations, including the Mongols, Tatars, Kereyid, Naiman and Merkit. They herded horses, sheep and other livestock, moved seasonally, and fought raids and feuds. The main narrative source for the period is the Secret History of the Mongols, written in the thirteenth century. It is valuable but partly legendary, and it was composed within the ruling family, so it is not a neutral record.
A man named Temujin rose out of this world. His birth year is uncertain, and scholars place it around 1162, with other proposals in the 1150s and 1160s. According to the tradition, his father was killed when he was young and his family endured hardship. Through alliances, battles and shrewd politics, Temujin defeated rival leaders over the next two decades. In 1206, at a great assembly called a kurultai, he was acclaimed ruler of the united tribes and took the title now written as Genghis Khan or Chinggis Khan.
Building an army and an order
The new state was organised around the army. Troops were grouped in decimal units, from tens up to units of ten thousand, and tribal loyalties were deliberately mixed to weaken old clan divisions. Promotion could depend on loyalty and skill as well as birth. A guard unit was formed from trusted followers, and Chinggis introduced a script for writing the Mongol language, adapted from that of the Uyghurs.
Mongol warriors were mostly horse archers, equipped with composite bows and several horses each, which allowed rapid movement across long distances. The army also learned siegecraft, often using engineers and specialists from conquered peoples, such as Chinese and Persian technicians. The Mongols’ military success depended on discipline, mobility, intelligence-gathering and the adoption of new methods, rather than on overwhelming numbers, which were often modest.
Campaigns under Genghis Khan
From 1206 the Mongols turned outward. Key stages included:
- Western Xia and the Jin. Campaigns against the Tangut state of Western Xia began around 1205-1209, and from 1211 the Mongols attacked the Jin dynasty of northern China. The Jin capital, Zhongdu (near modern Beijing), fell in 1215.
- Khwarazmia. After the killing of Mongol envoys and merchants in the Khwarazmian empire, a large Mongol army invaded Central Asia from 1219. Cities such as Bukhara, Samarkand, Merv and Nishapur suffered heavily, and the empire was overthrown within a few years.
- Raiding to the west. A force under Jebe and Subutai pursued the Khwarazmian ruler toward the Caucasus and defeated forces in the Caucasus and on the steppe north of the Black Sea in 1223.
Genghis Khan died in 1227 during a campaign against Western Xia. The place of his burial is not known with certainty.
The successors
The empire expanded after his death, though not always in a single line.
Ogedei (r. 1229-1241) was elected great khan after a regency period. The Jin state finally collapsed in 1234, and Karakorum was developed as a capital in Mongolia. In the west, Batu, a grandson of Genghis, led campaigns that struck the Rus principalities between 1237 and 1240, including the sack of Kyiv in 1240. Mongol armies then entered Poland and Hungary in 1241, winning battles at Legnica and Mohi. They withdrew after news of Ogedei’s death in late 1241, although historians debate the exact reasons for the retreat, and some suggest that supply, terrain and succession politics all played a part.
Mongke (r. 1251-1259) pushed campaigns toward Iran and China. His brother Hulegu led a large army into Persia and took Baghdad in 1258, ending the Abbasid caliphate in the city, a story linked to Abbasid Baghdad’s long history. In 1260 a Mamluk army defeated a Mongol force at Ain Jalut in Palestine, one of the few major checks on Mongol expansion in the west.
Kublai (r. 1260-1294) won a succession struggle, ruled from what is now Beijing, and completed the conquest of southern China, ending the Song in 1279. His dynasty is treated in a separate article on the Yuan dynasty China.
How the empire worked
Governing such a large area required systems that fitted the steppe tradition and adapted to local conditions.
- Relay communication. The yam was a postal and courier network with stations, horses and provisions, used to carry orders and officials across great distances. Travellers with the right authority could use it.
- Law and order. Tradition links Genghis Khan with a body of rules known as the yasa, but its precise content is debated, since our sources are later and partial.
- Taxes and census. The Mongols counted households and imposed levies in grain, labour and silver. Local officials often stayed in place under Mongol overseers.
- Religious tolerance. Buddhists, Muslims, Christians, Daoists and shamanists were generally permitted to worship, and religious leaders were sometimes exempted from taxes, although tolerance was practical and not unconditional.
- Trade and travel. Security on the main roads helped merchants and envoys, encouraging contact across Eurasia. The effect on Silk Road trade routes is often referred to as the Pax Mongolica, though the term can oversimplify a violent period.
Violence and its limits
Mongol campaigns brought heavy destruction, and some cities were destroyed after they resisted. Medieval chroniclers often gave very high death tolls, but their numbers are widely regarded as exaggerated, and modern historians remain cautious about figures. It is fair to say that the conquests caused serious loss of life and damage, while also recognising that the scale of any particular massacre is hard to measure. Cities that surrendered were frequently spared and taxed.
Division of the empire
After Mongke, the empire was no longer governed as one unit. Rival claims to the throne, distance and local ties led to four main khanates:
- the Yuan dynasty in China and Mongolia, under the line of Kublai;
- the Golden Horde in the western steppe, including Rus tribute lands;
- the Chagatai Khanate in Central Asia;
- the Ilkhanate in Iran and neighbouring regions.
These khanates sometimes fought one another. Over time most of their rulers adopted local religions and customs, with the Ilkhans and many in the Golden Horde and Chagatai lands turning to Islam, and the Yuan rulers drawing on Chinese and Tibetan Buddhist traditions. The Ilkhanate collapsed in the mid-fourteenth century, and the Yuan were driven from China in 1368, while others lasted longer.
Legacy
The Mongol era reshaped the political map of Eurasia, linked East and West through travel and commerce, and left descendants who ruled for centuries. The Timurid empire, established by Timur in the late fourteenth century, borrowed Mongol prestige even though its founder was not a direct descendant of Genghis Khan. Understanding the Mongol conquests means keeping several things in view at once: skilled organisation, exceptional mobility, terrible violence, and a surprisingly cosmopolitan government.