Genghis Khan's conquests resulted in an enormous death toll, with estimates commonly cited between 40 and 60 million people killed across the Mongol Empire's expansion

. This figure originates largely from historical population studies but is debated among scholars due to the lack of precise records and potential exaggerations in medieval sources

. Specific campaigns under Genghis Khan and his generals were marked by mass killings. For example, Persian historian Rashid al-Din recorded the deaths of over 1.3 million in Merv and nearly 1.75 million in Nishapur due to Mongol massacres

. The destruction of the Western Xia Tangut Empire also involved near-total extermination of its population, described as an early example of ethnocide

. While some medieval sources attribute extraordinarily high numbers of deaths to single battles or sieges-such as the claim that Genghis Khan killed 1,748,000 people in one hour-these are considered legends or exaggerations rather than factual accounts

. Overall, the Mongol conquests under Genghis Khan caused demographic catastrophes in many regions, with millions killed through warfare, massacres, and the resulting famine and social disruption

. Modern estimates suggest that about 30 percent of the populations encountered by the Mongols were killed during their campaigns

. In summary, while exact numbers are uncertain, scholarly consensus places the death toll attributable to Genghis Khan’s conquests in the tens of millions, with estimates commonly around 40 million people killed.