Who were the Mongols?

Under Genghis Khan, the Mongol army became a technologically advanced force and created the second-largest kingdom in history.

a mural depicting Genghis Khan

A modern mural in Inner Mongolia depicts the inauguration of Genghis Khan.

Photograph by James L. Stanfield, Nat Geo Image Collection
ByErin Blakemore
August 13, 2025

Mongols were known for warfare but celebrated for productive peace. Humble steppe dwellers, Mongol leaders mastered the era’s most advanced technology. Embodying these tensions helped turn the Mongol Empire into the second-largest kingdom of all time.

At its peak, the Mongol Empire covered the largest contiguous territory in history. Led at first by Genghis Khan, the empire lasted from the 13th century until the 14th century. During that time, it expanded to cover most of Eurasia, thanks to advanced technology and a massive horde of nomadic Mongol armies.

The rise of Genghis Khan

The Mongol Empire was founded in 1206, when Temüjin, son of a chieftain, assumed power and changed his name to Chinggis Khan (styled as “Genghis Khan” in the West and meaning “universal ruler”).

The young warrior had already defeated the Mongols’ most powerful leader and fomented dissatisfaction among his people’s aristocracy. But he proved to be not just one of the great khans, but one of history’s greatest leaders.

At the time, Mongolia’s nomadic tribes relied on the land to sustain them. Their flocks of goats, sheep, horses, and other animals were dependent on abundant grass and water, and Mongols had to travel frequently to sustain them. Drought and disease could quickly wipe out their livelihoods.

(She was Genghis Khan’s wife—and made the Mongol Empire possible)

Genghis Khan helped allay this sense of precariousness. He united Mongolia’s tribes and supported China’s peasant economy by stabilizing taxes and establishing rural cooperatives.

He reformed his people’s laws and ushered in a military-feudal form of government. He embraced trade and religious freedom, and adopted advanced technology of the time, such as stirrups, composite bows, leather armor, and gunpowder.

Genghis Khan’s loyal warriors were rewarded for their fealty and became the most successful army of their time.

a giant statue of Genghis Khan

A statue of Genghis Khan in Tsonjin Boldog near Ulan Baator and Erdenet in the Tov province, Mongolia.

Photograph by Joel Saget, AFP/Getty

Expansion of the Mongol Empire

Their success rested on a complex new military structure and new military tactics, like arrow storms, amassing huge arsenals, engaging in repeated hit-and-run barrages, delayed sieges, and psychological warfare.

The warriors were assisted by new technologies like the stirrup (which became status symbols) and technological and tactical innovations they adopted from the people they conquered through various military campaigns.

(Did the Great Wall of China keep the Mongols at bay?)

Traditional wisdom holds that the Mongols began growing their empire due to inhospitable conditions in their homeland among the steppes of central Asia. But more recent research suggests the empire had an unexpected boon: climate.

Researchers think the Mongol hordes may have initially prevailed due to a 15-year-long stretch of mild weather and above-average moisture that produced abundant grasses for their horses and better conditions for livestock breeding.

(Why the unstoppable Mongol Empire halted their European conquest)

How the Mongols were defeated

Genghis Khan’s death in 1227 ultimately doomed the empire he founded. His death marked the end of a vast empire that had flourished for 162 years of aggressive expansion. At the empire’s peak, Mongols controlled up to 12 million square miles across most of the known world at the time.

Despite its reputation for brutal warfare, the Mongol Empire briefly enabled peace, stability, trade, and protected travel under a period of “Pax Mongolica,” or Mongol peace, beginning in about 1279 and lasting until the empire’s end.

(Kublai Khan did what Genghis could not—conquer China)

Disputes among his successors eventually split the empire into four main khanates. By 1368, all four had folded, giving rise to the Ming Dynasty.

What the Mongols achieved

The Mongol Empire had gained a reputation for destroying its enemies, and it “spread terror and panic as news of the cities they had razed preceded them,” writes historian Diana Lary, a professor emerita at the University of British Columbia.

She notes that the Mongols sparked large migrations, not just of displaced people but also of those fleeing future attacks. Memories of these attacks loomed large in the imaginations of future generations.

(Genghis Khan has roughly 16 million descendants living today)

But the Mongol Empire left other legacies: the Silk Road and its history of trade; cultural development; and the potential for a modern era characterized by the unity of disparate peoples, and relative peace.

In Genghis Khan, the Mongol Empire also left behind the indelible impact of one of history’s greatest military leaders.

This story originally published on June 21, 2019. It was updated on August 13, 2025.