In 1279 AD, 24 million square kilometers and a quarter of the living human population were under the leadership of a single sovereign: Kublai Khan, immortalized in the eponymous poem by Coleridge. It was the largest contiguous empire ever to exist, twice the size of the Roman Empire, and the largest overall after the British Empire.

This immense power was almost entirely the result of the exploits of Kublai's far more famous and feared grandfather: Temüjin, better known as Genghis Khan. The genocidal ruthlessness of Temüjin transcended the ethnic and familial conflicts that plagued the clans of Mongolia, directing his predatory violence towards expansionist goals pursued with efficiency. By the early 1200s, it was quite common among the Mongols to believe that by uniting, they would achieve enormous military power.

Posing as an emissary of Tengri, the sky god, Temüjin replaced the traditional system of tribal loyalty with a new hierarchical power structure. Similar to what later occurred in the Ottoman Empire, the complete governmental centrality allowed individuals of humble origins to attain the highest positions, to the detriment of the blood nobility. The Great Khan had not only a brutal approach but also a practical one. Equipment such as the composite bow and silk armor, along with the extensive use of sophisticated siege machines, made his army innovative. The horde exterminated around 40 million people, obliterated splendid Middle Eastern cities like Merv, and crushed the Tangut civilization in China, sweeping away its magnificent monuments and burning its libraries. However, he allowed surviving authors from the subjugated civilizations, such as the Persian historian ʿAṭā Malik Juwaynī, to recount these events in great detail, precisely to terrorize potential enemies. He reopened the Silk Road, placed it under control, and unified the bureaucracy of the conquered territories. During the Pax Mongolica, in the first half of the 14th century, Asia experienced a phase of low conflict and flourishing exchanges, although built on mountains of skulls created as a macabre imitation of the tengrist ovoo.