Genghis Khan unified the warring nomadic tribes of the Mongol steppe in 1206, creating a military machine that would soon reshape the world. Before this unification, the region was a chaotic patchwork of competing groups like the Merkits, Tatars, Keraites, and Naimans, each fighting for dominance over the grasslands. The rise of the Mongols was not merely a political shift but was preceded by fifteen years of unusually wet and warm weather from 1211 to 1225. This climatic window allowed for the breeding of massive numbers of horses, providing the essential fuel for their cavalry-based expansion. Without this specific period of favorable weather, the logistical capacity to sustain such a vast army might have been impossible. The Mongol Empire was a land power fueled by grass-foraging cavalry and cattle, meaning most conquests and plundering took place during the warmer seasons when grazing was sufficient. This environmental dependency shaped the rhythm of their warfare, contrasting sharply with the later European empires of the sea that relied on naval power and trade routes.
The Quota of Death
The Mongol strategy for subjugating cities was not just about destruction but about a systematic, quota-based execution of populations. When a city resisted, the Mongols would destroy it entirely, and every soldier was given a specific number of enemies to execute according to the circumstances. For example, after the conquest of Urgench, each Mongol warrior in an army of perhaps two tumens, or 20,000 troops, was required to execute 24 people. This quota system resulted in nearly half a million people being killed by a single army. Large areas of Islamic Central Asia and northeastern Persia were seriously depopulated as a direct result of this policy. The Mongols did not merely conquer; they erased entire populations to ensure future compliance. This brutal efficiency was applied across Central Asia, where the Alans and Cumans were targeted using divide-and-conquer tactics. The Mongols first warned the Cumans to end their support of the Alans, whom they then defeated, before turning their full force against the Cumans. The Alans were subsequently recruited into the Mongol forces and known as the Asud, with one unit called the Right Alan Guard combined with recently surrendered soldiers.
The Siege of Baghdad
The Mongol conquest of the Middle East reached its zenith with the siege of Baghdad in 1258, a city that had been the center of Islamic power for 500 years. Hulagu Khan led the campaign with the support of one thousand North Chinese engineer squads, bringing advanced siege technology to the region. The Mongols sacked the city, marking a turning point in the history of the Islamic world. This campaign was part of a broader strategy that included raids reaching southwards into Palestine as far as Gaza in 1260 and 1300. However, the Mongol advance was not unstoppable. The Battle of Ain Jalut in 1260 in southeastern Galilee saw the Muslim Bahri Mamluks defeat the Mongols and decisively halt their advance for the first time. The Mamluk military was largely composed of Kipchaks, and the Golden Horde's supply of Kipchak fighters replenished the Mamluk armies, helping them fight off the Mongols. This battle demonstrated that the Mongol invasions could be stopped, even if the cost was immense. The Mongol Empire's reach extended to modern-day Iran, Iraq, the Caucasus, and parts of Syria and Turkey, but the Mamluk resistance in Egypt and Syria proved to be a formidable barrier.
In East Asia, the Mongols launched progressive invasions that subjugated the Western Xia in 1209 before destroying them in 1227, and defeated the Jin dynasty in 1234. The Song dynasty fell in 1279, completing the Mongol conquest of China. Kublai Khan established the Yuan dynasty in 1271, creating a Han Army out of defected Jin troops and an army of defected Song troops called the Newly Submitted Army. The Mongol force which invaded southern China was far greater than the force they sent to invade the Middle East in 1256. The Mongols also made the Kingdom of Dali into a vassal state in 1253 after the Dali King Duan Xingzhi defected to the Mongols and helped them conquer the rest of Yunnan. Korea was forced to capitulate through nine invasions, becoming a semi-autonomous vassal state of the Yuan dynasty for about 80 years. Despite their success on land, the Mongols failed in their attempts to invade Japan, their fleets scattered by kamikaze storms. The Yuan dynasty also established the Bureau of Buddhist and Tibetan Affairs to govern Tibet, which was conquered by the Mongols and put under Yuan rule. The Mongols invaded Sakhalin Island between 1264 and 1308, extending their reach to the far north of Asia.
The Forest and the Steppe
By 1206, Genghis Khan had conquered all Mongol and Turkic tribes in Mongolia and southern Siberia. In 1207, his eldest son Jochi subjugated the Siberian forest people, including the Uriankhai, the Oirats, Barga, Khakas, Buryats, Tuvans, Khori-Tumed, and Yenisei Kyrgyz. He organized the Siberians into three tumens and gave the Telengits and Tolos along the Irtysh River to an old companion, Qorchi. The Khagans favored gyrfalcons, furs, women, and Kyrgyz horses for tribute. Western Siberia came under the Golden Horde, ruled by the descendants of Orda Khan, the eldest son of Jochi. In the swamps of western Siberia, dog sled yam stations were set up to facilitate collection of tribute. In 1270, Kublai Khan sent a Chinese official to serve as judge of the Kyrgyz and Tuvan basin areas. Ogedei's grandson Kaidu occupied portions of Central Siberia from 1275 on, and the Yuan dynasty army under Kublai's Kipchak general Tutugh reoccupied the Kyrgyz lands in 1293. From then on, the Yuan dynasty controlled large portions of Central and Eastern Siberia. The Mongol conquest of the Kipchaks led to a merged society with a Mongol ruling class over a Kipchak-speaking populace which came to be known as Tatar, and which eventually absorbed Armenians, Italians, Greeks, and Crimean Goths in Crimea, the origin of the current Crimean Tatars.
The Southern Frontiers
From 1221 to 1327, the Mongol Empire launched several invasions into the Indian subcontinent, occupying parts of northwestern South Asia for decades. However, they failed to penetrate past the outskirts of Delhi and were repelled from the interior of India. Centuries later, the Mughals, whose founder Babur had Mongol roots, established their own empire in India. Kublai Khan's Yuan dynasty invaded Burma between 1277 and 1287, resulting in the capitulation and disintegration of the Pagan Kingdom. The invasion of 1301 was repulsed by the Burmese Myinsaing Kingdom. The Mongol invasions of Vietnam and Java resulted in defeat for the Mongols, although much of Southeast Asia agreed to pay tribute to avoid further bloodshed. The Mongol invasions played an indirect role in the establishment of major Tai states in the region by recently migrated Tais, who originally came from Southern China, in the early centuries of the second millennium. Major Tai states such as Lan Na, Sukhothai, and Lan Xang appeared around this time. The Mongol Empire's influence extended to the Indian subcontinent, but the geography and local resistance prevented total conquest.
The European Cataclysm
The Mongols invaded and destroyed Volga Bulgaria and Kievan Rus', before invading Poland, Bulgaria, Hungary, and other territories. Over the course of three years from 1237 to 1240, the Mongols razed all the major cities of Russia with the exceptions of Novgorod and Pskov. The Mongol invasions displaced populations on a scale never seen before in Central Asia or Eastern Europe. Word of the Mongol hordes' approach spread terror and panic. The violent character of the invasions acted as a catalyst for further violence between Europe's elites and sparked additional conflicts. The increase in violence in the affected Eastern European regions correlates with a decrease in the elite's numerical skills, and has been postulated as a root of the Great Divergence. Hungary became a refuge for fleeing Cumans. The decentralized, stateless Kipchaks only converted to Islam after the Mongol conquest, unlike the centralized Karakhanid entity comprising the Yaghma, Qarluqs, and Oghuz who converted earlier to world religions. The Mongol invasions in Europe led to the construction of mighty stone castles, such as Spiš Castle in Slovakia, as a defensive response to the threat.
The Silent Toll
Due to the lack of contemporary records, estimates of the violence associated with the Mongol conquests vary considerably. Not including the mortality from the Black Death in Europe, West Asia, or China, it is possible that between 20 and 60 million people were killed between 1206 and 1405 during the various campaigns of Genghis Khan, Kublai Khan, and Timur. The campaigns killed a large number of people and involved battles, sieges, early biological warfare, and massacres. The book from which the figures originate has been criticized for its methodology and the Chinese censuses on which the estimates are based are considered unreliable. Nevertheless, the campaigns killed a large number of people and involved battles, sieges, early biological warfare, and massacres. The Mongol Empire developed in the course of the 13th century through a series of victorious campaigns throughout Eurasia. At its height, it stretched from the Pacific to Central Europe. It was later known as the largest contiguous land empire of all time. As the Mongol Empire began to fragment from 1260, conflict between the Mongols and Eastern European polities continued for centuries. Mongols continued to rule China into the 14th century under the Yuan dynasty, while Mongol rule in Persia persisted into the 15th century under the Timurid Empire. In the Indian subcontinent, the later Mughal Empire survived into the 19th century.