Genghis Khan and the Mongol Empire
10 Popular Claims, Checked

The Mongol Empire built in the 13th century by Genghis Khan and his successors was, in the words of the historian David Morgan, “the most extensive land empire known to history”. It is also the subject of a great many confident claims. Here are ten of the most repeated, checked against the medieval sources and the modern studies behind them.

1. “1 in 200 men alive today are descended from Genghis Khan”

Disputed The figure comes from a 2003 study in the American Journal of Human Genetics of a single Y-chromosome lineage, passed from father to son. The authors found that “approximately 8% of the men in this region carry it, and it thus makes up approximately 0.5% of the world total”. But the headline number comes with a condition, “if our sample is representative”, and the link to Genghis Khan was an inference: “The available evidence suggests that it was carried by Genghis Khan.” They also noted that “It is not possible to examine his remains directly”.

Later work has pulled both ways. A 2018 whole-sequence study in the European Journal of Human Genetics dated the lineage’s common ancestor to about 2,576 years ago and concluded that “direct evidence of an association between C2*-ST and Genghis Khan has yet to be discovered.” A 2026 study in PNAS of ancient DNA from Golden Horde elite tombs in Kazakhstan found the lineage in three related men, “confirming the association between the Y-chromosome haplogroup C3* and the Mongol Empire”, and its authors think Genghis Khan’s father’s line most likely belonged to this group, though “conclusive evidence for any specific haplotype … remains lacking”. The lineage is linked to the Mongol ruling class; that it was Genghis Khan’s own remains unproven.

Even taken at face value, the claim is about one line of fathers and sons, not about everyone descended from him.

2. “Genghis Khan cooled the planet”

Myth A 2011 modelling study in The Holocene looked at whether wars and epidemics, including “the Mongol invasion (~1200 to ~1380)”, changed carbon dioxide levels as abandoned farmland grew back into forest. Its title already gives the answer: “minor global effects”. The authors found that “Only the Mongol invasion could have lowered global CO2, but by an amount too small to be resolved by ice cores.”

Its abstract reports a change in carbon dioxide too small to detect in ice cores, not a change in temperature. The study’s press release did not claim cooling either. It said the Mongols “had an impact on the global carbon cycle as big as today’s annual demand for gasoline”, and added a caveat: “The global impact of forest re-growth in even the long-lasting events was diminished by the continued clearing of forests elsewhere in the world.”

3. “Genghis Khan was his name”

Myth It was a title. According to The Secret History of the Mongols, the 13th-century Mongol chronicle, he was named Temüjin after a captive his father had just taken. The chronicle says his followers first made him khan, “naming him Cinggis Qa’an”, years before 1206; in the Year of the Tiger, 1206, an assembly at the source of the Onan River confirmed him as khan over all the peoples he had united. His birth year is not known: Igor de Rachewiltz, the chronicle’s translator, gives “probably in 1162”, while Morgan, in the Encyclopaedia Iranica, gives “probably born in 562-63/1167”. He died in 1227, during his last campaign, against the Tangut, and no portrait made in his lifetime survives.

4. “The Mongols killed 40 million people”

Unverified We could not trace this figure to a count of the dead in any source we could read. The medieval numbers for single cities run into the millions: the historian Juvaini, writing in the 1250s, says the dead at Merv took “thirteen days and nights” to count and came to more than 1.3 million, and other chroniclers give different totals for the same cities. Morgan’s judgement is that “Such statements should not be taken too literally” and that “it may be doubted that anyone was counting.”

That caution cuts one way only. Morgan adds: “What cannot be doubted, however, is that the death and destruction was on a scale quite beyond contemporaries’ previous knowledge or experience.”

5. “Genghis Khan wrote a law code, the Yassa”

Disputed Juvaini says the rules were to “be written down on rolls”, and that “These rolls are called the Great Book of Yasas and are kept in the treasury of the chief princes.” He was describing his own day, the 1250s, and he was born “in all probability, in the year 1226”, a year before Genghis Khan died. He is also, in the historian Peter Jackson’s words, “virtually our only source on the yāsā”. Historians read that evidence differently. Morgan concludes: “It no longer seems possible to ascribe to him the creation of a written legal code”, and that Mongol law “appears to have had a much more customary and ad hoc character”. Jackson, in the Encyclopaedia Iranica’s entry on the Yasa, notes that “there is nothing incongruous in the possibility that edicts were written down”, and says they came to be regarded, “if not as a homogeneous and systematically organized code, at least as a recognizable corpus of regulations”. The evidence leans against a single written law code drawn up by Genghis Khan himself, because Juvaini is almost the only witness; that his rulings were recorded and kept is quite possible.

6. “The Mongols were religiously tolerant”

Partly true Mongol rulers backed clergy of many faiths. Juvaini says Genghis Khan “honoured and respected the learned and pious of every sect”, and the Mongols, according to Columbia University’s Mongols in World History teaching resource, “even offered tax benefits to the clerics of Buddhism, Islam, Daoism, and Nestorian Christianity in order to win the support of those religions.”

The friar William of Rubruck, who travelled to the Mongol court in 1253–55, heard the Great Khan Möngke (whom he calls Mangu) explain his view in person: “But as God gives us the different fingers of the hand, so he gives to men divers ways.”

It had limits. Juvaini records that the Mongol khan Chaghatai enforced rules that no one might slaughter meat in the Muslim way or sit by day in running water, which Juvaini calls “an intolerable imposition” on his Muslim subjects. Tolerance here was a governing policy, not a right.

7. “The Mongols never bathed”

Myth The sources describe a specific taboo, not a lack of washing. Juvaini writes that “in the season of spring and summer no one may sit in water by day, nor wash his hands in a stream, nor draw water in gold or silver vessels, nor lay out washed garments upon the plain”, because of the belief “that such actions increase the thunder and lightning”.

William of Rubruck, writing separately from the Mongol court, reports the same rule and the same reason: “They never wash clothes, for they say that God would be angered thereat, and that it would thunder if they hung them up to dry.” Rubruck also describes how they did wash: “When they want to wash their hands or head, they fill their mouths with water, which they let trickle on to their hands, and in this way they also wet their hair and wash their heads.”

8. “The Mongols started the Black Death by throwing plague corpses into Caffa”

Myth The story of the 1346 siege of Caffa, in Crimea, comes from one account by a notary in Piacenza, Gabriele de’ Mussi. In a modern English translation, the besiegers “ordered corpses to be placed in catapults and lobbed into the city”. Mark Wheelis of the University of California, Davis, reviewing the account in 2002, found that de’ Mussi “does not claim to have witnessed any of the Asian events he describes” and that his “account is probably secondhand and is uncorroborated”.

Wheelis thought the attack plausible, and “the best explanation of the entry of plague into the city”, but concluded that the siege was “unlikely to have been seriously implicated in the transmission of plague from the Black Sea to Europe”. A 2022 study in Nature traced the pandemic’s origin to central Eurasia, where “tombstone inscriptions directly dated to 1338-1339” name pestilence as the cause of death, and said that “the exact means through which Y. pestis reached western Eurasia are unknown”. The besiegers were the army of the Mongol ruler Janibeg, whose Golden Horde was one of four parts the empire had split into by 1260, and the plague was already in that army: Wheelis records that the siege was lifted because of “an epidemic of plague that devastated his forces”. So the corpse story may be true, but the Black Death did not start at Caffa.

9. “A divine wind saved Japan from the Mongols”

Partly true In 1281 a storm did wreck much of Kublai Khan’s second invasion fleet. A Korean chronicle, the Goryeo-sa, records that the southern army “met with large wind, and all the Southern Army died”. Some historians give the defenders more of the credit: several scholars, Sasaki notes, have suggested that coastal stone walls and “the small fast boats that the Japanese used” had already kept the army from landing in force. The 1281 wrecks at Takashima show a mixed fleet: a large cargo ship from Fujian, “strongly built Korean vessels”, and many smaller hulls that Sasaki thinks were mostly built along the Yangtze and “not constructed for long overseas voyages”.

The first invasion, in 1274, is less clear. According to the historian Hattori Hideo, Korean records mention a typhoon, and he argues that the army stayed seven days and then withdrew because of it; others read the landing as reconnaissance. In a study of the wrecks, the archaeologist Randall Sasaki writes that “The true reason for this retreat is difficult to identify”: the official Yuan history says “the troop was not organized” and “all the arrows had been used”, and one reading treats that landing as “more in the nature of a raid than a full-scale invasion”.

10. “The Mongols left Europe in 1242 because the Great Khan died”

Disputed The long-standing explanation is that the army turned back so its leaders could take part in choosing a new khan after the Great Khan Ögedei died. The historian Stephen Pow, in a 2012 thesis, argues that “these theories are unconvincing and contradicted by the existing primary source evidence”. He points to the historian Rashid al-Din, who says that when one Mongol force turned back, “the news of Khan’s death had not yet reached them”. Pow suggests instead that “European fortifications produced a strategic problem”. A third explanation, from a 2016 study of tree rings and written records, points to cold, wet conditions in early 1242 that turned the Hungarian plain to marsh; a team including Pow disputed it in 2017. Historians have not settled it.

Our reading

The Mongol conquests do not need exaggerating. The destruction was, as Morgan puts it, beyond anything contemporaries had known, and the empire was also a system of relay stations, clerical tax privileges and religious debate. The myths flatten both sides: they turn a conditional DNA estimate into a fact, a carbon model into a cooled planet, one notary’s story into the origin of the Black Death, and a thunder taboo into dirt. To Mongols, Genghis Khan is a great national hero; elsewhere he is remembered for the killing. Both are part of the record, and we give no verdict on the man.

Sources

• Tatiana Zerjal et al., “The genetic legacy of the Mongols”, American Journal of Human Genetics 72(3) (2003).
• Lan-Hai Wei et al., “Whole-sequence analysis indicates that the Y chromosome C2*-Star Cluster traces back to ordinary Mongols, rather than Genghis Khan”, European Journal of Human Genetics 26(2) (2018).
• Julia Pongratz, Ken Caldeira, Christian H. Reick and Martin Claussen, “Coupled climate–carbon simulations indicate minor global effects of wars and epidemics on atmospheric CO2 between AD 800 and 1850”, The Holocene 21(5) (2011), abstract; and Carnegie Institution for Science press release, 20 January 2011 (archived).
• The Secret History of the Mongols, trans. Igor de Rachewiltz, shorter version ed. John C. Street (2015), CC BY-NC-ND 4.0.
• David O. Morgan, “Čengīz Khan”, Encyclopaedia Iranica V/2 (1990, updated 2013).
• Peter Jackson, “Yāsā”, Encyclopaedia Iranica (2013, updated 2017).
• ʿAtā-Malik Juvaini, The History of the World-Conqueror, trans. John Andrew Boyle, vol. 1 (Manchester University Press, 1958).
• The Journey of William of Rubruck to the Eastern Parts of the World, 1253–55, trans. William Woodville Rockhill (Hakluyt Society, 1900).
• Columbia University, Asia for Educators, The Mongols in World History.
• Mark Wheelis, “Biological Warfare at the 1346 Siege of Caffa”, Emerging Infectious Diseases 8(9) (2002).
• Ayken Askapuli et al., “Genomes of the Golden Horde elites and their implications for the rulers of the Mongol Empire”, PNAS 123 (2026).
• Maria A. Spyrou et al., “The source of the Black Death in fourteenth-century central Eurasia”, Nature 606 (2022).
• Kawai Atsushi, “Saved by the Wind? The Mongol Invasions of Japan”, Nippon.com (2021).
• Randall James Sasaki, The Origin of the Lost Fleet of the Mongol Empire, MA thesis, Texas A&M University (2008).
• Ulf Büntgen and Nicola Di Cosmo, “Climatic and environmental aspects of the Mongol withdrawal from Hungary in 1242 CE”, Scientific Reports 6 (2016); and Zsolt Pinke et al., “Climate of doubt”, Scientific Reports 7 (2017).
• Lindsey Stephen Pow, Deep Ditches and Well-built Walls: A Reappraisal of the Mongol Withdrawal from Europe in 1242, MA thesis, University of Calgary (2012).

Checked September 2026.

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