The Mongols under Genghis Khan were fearsome conquerors who razed cities and took millions of lives, but the Mongol Empire also established a lasting peace that shaped history. While we often think of the Mongols as fearsome barbarians who vanquished any who opposed them, they were also surprisingly tolerant rulers. The Mongols promoted trade and diplomacy across their vast empire, leading to flourishing trade on the Silk Road. Genghis Khan himself established religious tolerance in the empire, and often placed the governance of his territories in the hands of conquered peoples. But the Mongol emphasis on travel and their expansive reach undoubtedly had negative effects; along with conquest and conflict, they may have spread diseases like the bubonic plague across Eurasia and unintentionally caused the Black Plague of 1348.
Genghis Khan single-handedly transformed the Mongols from a collection of nomadic tribes into a conquering force. Battle after battle, the Mongols demonstrated the dominance of their light cavalry, showing off their tactics and precision by luring enemies into ambushes. While the empire lasted less than two hundred years, Mongol influence lasted for centuries after it crumbled, shaping European, Chinese, and Middle Eastern history for generations.
In only about 25 years, Genghis Khan managed to seize more land than the Roman Empire captured in over 400 years. As Mongol emperor, Genghis Khan conquered around 12 million square miles of land. He created the largest empire in history using just 100,000 men.
Under Genghis Khan, Mongol forces ended so many lives that fields went unplowed and the land reverted back to forests. In fact, climate scientists report that the depopulation was significant enough to actually cool the planet, because the trees absorbed so much carbon dioxide.
The Mongols were incredibly destructive. During his conquests, Genghis Khan took an estimated 37.5 million lives; however, the Mongols also instituted an empire that unified much of Asia for the first time. Known as the Pax Mongolica, or "Mongol Peace," the Mongol domination let trade flourish on the Silk Road. For the first time, one power ruled the entire length of the Silk Road, making it much safer than ever before.
Trade flourished, and the Mongols boasted that a maiden carrying a gold nugget in her hand could cross from one end of the empire to the other without being harmed.
The Plague originated in China when it was ruled by the Mongol Yuan Dynasty. Within three years of the disease's emergence, 90% of Hebei province's entire population had perished. Ironically, Mongol protection of Silk Road trade helped the disease spread.
The disease traveled with caravans to Middle Eastern trading centers, where Egyptian scholar Al-Mazriqi reported, "More than three hundred tribes all perished without apparent reason in their summer and winter encampments, in the course of pasturing their flocks and during their seasonal migration."
Along with the unintentional consequences of unfettered trade, the Mongols played an even more active role in spreading the disease. During a years-long siege of the Genoese-held city of Kaffa in 1347, the Mongol Golden Horde used germ warfare on the port city.
According to Italian lawyer Gabriele de Mussis, the Mongol leader "ordered corpses to be placed in catapults and lobbed into the city in hopes that the intolerable stench would [wipe out] everyone inside." The disease spread, and soon, "the [troops were] affected by a disease which overran the Tartars and [claimed] thousands upon thousands every day."
When the Genoese abandoned Kaffa to return to Italy, they carried the Plague with them.
Genghis Khan might have stopped his conquest at the border of the Khwarezmid Empire in modern Northeastern Iran, but it was only due to a slight by the empire's ruler that Genghis Khan continued to expand his territory. He sent a diplomatic message to Shah Ala ad-Din Muhammad that read, "I am master of the lands of the rising sun, while you rule those of the setting sun. Let us conclude a treaty of friendship and peace."
After accepting the treaty, the Shah wiped out a Mongol trade caravan in 1219. The Mongol ruler sent diplomats demanding restitution, but the Shah ended them and sent their heads back to the Great Khan. The Mongols responded by marching into Persia, taking out Shah Muhammad and completely conquering the Khwarezmid Empire.
While the Mongols were remarkably flexible about adopting bureaucracies and religions from conquered regions, they placed a high value on trade and law - and when the Shah took the lives of traders and diplomats, he was faced with the Mongol wrath.