Of history’s most outstanding military leaders, Genghis Khan holds the distinction of conquering more territory than any other. The famed Mongol ruler is known for his brutal tactics and swift cavalry, but his rise to power was also because of his clever politics and bold leadership. There was a time when the first Khan seemed happy to sign a peace treaty and trade agreement with his neighbor to the west, focusing his efforts on China. But, when the neighboring kingdom’s ruler broke their deal, the Khan responded with perhaps his most famous military campaign ever. The conquest of Khwarezmia was Genghis Khan’s revenge tour, leading to Mongol dominance throughout Asia and, ultimately, the largest empire in history.
Genghis Khan was born in a nomadic tribe on the Mongolian plateau around the year 1162, bearing the name Temujin. Over the next several decades, he grew in stature, both physically and reputationally. Mongolia was comprised of dozens of tribes, constantly fighting amongst themselves, with little ambition of expanding outside their homeland. However, as Temujin advanced within his own tribe, he showed contempt for the ways of the past. Instead of appointing family members to leadership positions, he assigned men based on competence. He executed anyone who threatened his authority and established laws to cut down on feuds between tribes. Then, in 1206, he united Mongolia’s clans under a single banner, becoming the sole leader of the plateau’s 1-million residents, and adopting the title Genghis Khan, or Universal Ruler.
With their horse-archers, lightning-quick attacks, and clever tactics, the Khan’s armies began to swallow up territory with ease. After several campaigns to the southeast in China, the Khan turned his attention west. The conquest of Qara Khitai showed that Genghis’s reputation preceded him. Many of the region’s peoples submitted to the Mongols, declaring allegiance to the ruler rather than facing his horde’s wrath. As the Khan extended his lands into Central Asia, his borders approached those of another powerful ruler.
The Shah Ala ad-din (Allah-uh-deen) Muhammed of Khwarezmia was growing his empire, which stretched from modern-day Pakistan in the south to Iran’s western border and north into Khazakstan. Both leaders controlled stretches of the Silk Road, and it was evident to Genghis that the two could form a profitable partnership. The Khan grew richer by the day from trade originating and ending in his lands, but the Silk Road was often dangerous for merchants. So, the Mongol ruler attempted to formalize the partnership with a treaty between the two empires. The arrangement would formally establish peace and open trade between the two peoples and allow merchants from both lands to travel throughout the other with less threat of being killed or having their goods stolen.
Shah Muhammed was wary of Genghis Khan, though, as his ambassadors in Beijing had sent word of Mongol brutality to Khwarezmia. Still, the Shah agreed to the treaty, and Genghis immediately increased trade through the region, sending a caravan of at least 500 men through his new allies’ lands.
But the caravan never made it to its destination. While in the city Otrar, the first Khwarezmian city they reached, the entire procession was arrested by the governor Inalchuq, an uncle of the Shah. He charged that the merchants were actually a group of spies from Mongolia. With approval from the Shah, Inalchuq executed all 500 men and seized their goods.
In response, the Khan sent three ambassadors, one Turkic Muslim, and two Mongols. When these men arrived in Otrar, they requested that the local governor turn himself in for the blatant violation of the treaty. Instead, Inalchuq beheaded the Muslim and shaved the Mongols bare before sending them back to their homelands. This was a grave violation in the Khan’s eyes. After all, in war, all things were fair. However, he believed ambassadors were “sacred and inviolable,” even in enemy lands. This blatant betrayal would have consequences.
The Mongol horde was in China at the time, wrapping up a campaign against the Jin empire, but the Shah’s actions forced Genghis to rearrange his priorities. He left one of his generals with 20,000 men to finish the conquest in China and led the rest of his troops east.
At this point, it’s important to note that historians disagree over the size of the armies. Sources from the time claimed that Genghis Khan’s horde totaled 6 to 700,000 men, with the Shah’s army around 400,000. Modern authorities cut these numbers dramatically to something like 75,000 to 200,000 for the Mongols and 40-60,000 for Khwarezmia.
Besides the potential numbers edge, the Mongols also had two key advantages. First, the Shah had only recently seized control of much of his northern territory, and he was concerned that the men there might turn on him. At best, they weren’t as organized and unified as the Mongol troops. Second, many of the Shah’s cities lacked the fortifications that Khan’s were used to facing in China. Genghis Khan’s early conquests showed his inability to mount a proper siege, but his conflicts in China gave him experience in that arena, where sieges sometimes lasted years. Without adequate walls and fortresses, that time could be cut to months.
While the Mongols began their advance, the Shah assembled his military leaders to plan strategy. The Khwarezmians had three options. They could combine all their forces and march to meet the Mongols where they wouldn’t expect it. They could withdraw to the mountains of Afghanistan, the portion of the empire with the best fortifications. Instead, the Shah chose to spread out his armies to the realm’s cities, perhaps in fear of losing control of the disloyal northerners.
In 1219, part of the Khan’s army crossed the Tian Shan mountains and entered Khwarezmian territory around modern-day Khazakstan. The crossing was no easy feat. Two of Genghis’s children led the force, who directed their troops across the mountain range in the dead of winter, through five feet of snow. The maneuver shocked the Shah and his generals, as they believed the mountains to be impassable at that time of year. Instead, it became the Mongol version of Hannibal leading his troops across the Alps. The Shah sent a cavalry division to intercept, but he hadn’t realized that this was a diversion.
The main Mongol horde initiated an attack on the city of Otrar, on the Syr Darya river, the site where the caravan was initially killed. Genghis held back his own troops and allowed his two other sons to lead the siege, hoping to encircle the Shah’s army as they marched north from Samarkand to meet the Mongols in open battle. But, the Shah tactfully avoided this trap, and Otrar posed a substantial resistance. The siege lasted for five months until a traitor within Otrar opened the city gates so the Khan’s sons could march their troops inside and slaughter their enemies. Inalchuq, the governor who killed the men from the caravan, was captured and killed. Shah Muhammed, hearing of the destruction of Otrar, fled for his safety.
Genghis was famous for not sparing any enemy soldiers, regardless of their race or creed. Meanwhile, he sent craftsmen back to Mongolia to build tools and supplies for his armies, and unskilled laborers were used as arrow fodder, pushing siege weapons and acting as diversions.
With the Khwarezmian troops broken up across the empire’s cities, Genghis split his own force into five smaller divisions, dividing and conquering. The Khan’s next move was perhaps the most impressive maneuver of his entire career.
The city of Bukhara lay almost 500 kilometers away from Otrar, across the Kyzyl Kum desert. The Bukharans believed that the Kyzyl Kum couldn’t be traversed by such a large force, so the Khan led his army that way. With the help of local nomads, they hopped from oasis to oasis. When they arrived at the gates of Bukhara, the local military was shocked. While the siege of Otrar persisted five months, the battle at Bukhara lasted fifteen days.
At this point, another surprising advantage became clear. The Mongols, in their conquest of China, hadn’t just gained experience with siege tactics. They also adopted Chinese engineering and technology, including siege bows that fired 6 meter long arrows and catapults that heaved rudimentary bombs. But, Genghis also used psychological warfare.
Muhammed was not the undisputed ruler of his lands. The Shah’s mother, Tertun Khatun, was favored by the region’s Turkish people, and their elite cavalry divisions preferred to follow her over the Shah. The Khan sowed discord throughout the empire by spreading the word that Khatun had joined forces with the Mongols to fight against her own son. Whether or not Muhammed ever heard this news is unclear— shortly after Bukhara, the Shah fled his empire altogether, leaving the landmass for a tiny island in the Caspian Sea. Genghis sent a small horde to find the Shah, hunt him down, and kill him. Only later would they discover that the former ruler died of pneumonia shortly thereafter and would not live to see his empire’s collapse. Muhammed’s son, Jalal ad-Din Mingburnu, assumed control of the armies after his father’s death.
Of the following battles, those at Samarkand and Urgench were perhaps the most demanding. Both cities had more advanced fortifications than Otrar or Bukhara, and Urgench’s marshy land made it difficult to mount a proper siege.
This battle also marked a significant turning point in the Khan’s relations with his four sons. All glorified officers in their own right, the Khan’s eldest son, Jochi, believed that Urgench should fall under his rule. To keep the city intact, Jochi attempted to stop the bloodshed as early as possible, going against Mongol tradition. This angered a rival brother, and, in response, they massacred the entire population. Ancient historians claim that the number of lives lost that day eclipsed 1.2 million, though modern estimates set it below 10 percent of that. Still, the likely figure places it among the most deadly days in human history.
Following the battles in Central Asia of 1219, the Khan’s armies moved into Khorasan, in modern-day Iran, in 1220, then Afghanistan, in 1221. Jalal ad-Din led the Khwarezmian army in what would come to be their last stand in the well-fortified city of Parwan. Genghis sent an army led by his adopted brother, Shikhikhutag, who was inexperienced and outmanned. The new Shah led his troops to a victory that humiliated the Khan, who had won every previous battle of the campaign. So, Genghis Khan rode his own force to the Indus River, where he met Jalal ad-Din in open combat. The Mongols were victorious this time, but the previous loss showed the Khwarezmian people that the Khan was not invincible. They rose up in revolt, only to be crushed in the final days of the campaign. Jalal ad-Din, the lash Shah of Khwarezmia, was eventually hunted down and killed by Genghis’s son Ogedei.
Over the two-year conquest, the Mongols conquered an area of 4 million kilometers, including most of central Asia, and reaching the Caucasus. Now almost 60 years old, Genghis Khan returned to Mongolia, where he eventually waged another campaign against the Chinese Xi Xia dynasty. During battle, Genghis was thrown from his horse, suffering internal injuries that would ultimately cause his death in 1227. Ogedei, Genghis’s third son, was named the next Khan. Despite losing their first great leader, the Mongols would follow the first Khan’s example, picking up where Genghis left off. Over the next two decades, Mongol forces entered Europe, conquering lands as far as Poland and Croatia, compiling the largest contiguous land empire in the history of humankind.
But what would’ve happened if the Shah Muhammed had never violated his treaty with Genghis Khan— if he had known that his actions would provoke the most ferocious military-leader of his time? Perhaps Genghis would’ve conquered Khwarezmia anyway, or maybe he would’ve been satisfied with his profitable realm in East Asia. How would world history be different today if the Khan never lead his forces across the Tian Shan mountains, if the Mongols never dominated Eurasia? Would Genghis Khan be a footnote to westerners, only a key player in East Asian history?
We’ll never know. Instead, the Mongol Empire brought the peoples of Eurasia to their knees, and the first Khan etched his name in the history books forever.