Genghis Khan created an efficient military regime after his unifying rise to power in the nomadic Mongol territories of northeastern Asia in 1206 CE. These forces were no longer grouped by tribe or familial affiliation, but rather were organized into armies of multiples of ten soldiers that could be sent where needed in the name of Mongol expansion. Genghis Khan sent forces in every direction, including westward into central Asia. While he was fighting the Western Xia and Jin Dynasties in the east, he was also attempting to gain more land to the west in the Kara-Khitan Khanate and the Khwarazmian Empire, regions that comprise modern-day Iran, Iraq, and Uzbekistan.

Conquest of the Kara-Khitan Khanate

The Mongol Empire conquered the Kara-Khitan Khanate, an empire comprised of former nomads in Central Asia, in the years 1216-1218 CE. The khanate was under the rule of Prince Küchlüg, who had converted to Buddhism and had been persecuting the Muslim majority among the Khitan. This alienated him from most of his people, creating ideal circumstances for a takeover by Genghis Khan.

The Kara-Khitai attracted Genghis Khan’s attention when they besieged Almaliq, a city belonging to vassals of the Mongol Empire. Genghis Khan dispatched an army, who, under the command of General Jebe, defeated the Kara-Khitai at their capital, Balasagun, and Küchlüg fled. Jebe gained support from the Kara-Khitan populace by announcing that Küchlüg’s oppressive policy of religious persecution had ended. When his army followed Küchlüg to Kashgar in 1217, the populace revolted and turned on Küchlüg, forcing him to flee again for his life. Jebe pursued Küchlüg into modern Afghanistan. According to Persian historian Ata-Malik Juvayni, a group of hunters caught Küchlüg in 1218 and handed him over to the Mongols, who promptly beheaded him.

With Küchlüg’s death, the Mongol Empire secured control over the Kara-Khitai and surrounding areas. The Mongols now had a firm outpost in Central Asia directly bordering the Khwarazmian Empire, in Greater Iran. Relations with the Khwarazms would quickly break down, leading to the Mongol invasion of that territory in 1219.

Conquest of the Khwarazmian Empire

In the early 13th century, the Khwarazmian Empire was governed by Shah Ala ad-Din Muhammad. Genghis Khan saw the potential advantage in Khwarazmia as a commercial trading partner using the Silk Road, and he sent a caravan to establish official trade ties with the empire. However, a Khwarazmian governor attacked the caravan, claiming that it contained spies. Genghis Khan sent a second group of ambassadors to meet the Shah himself instead of the governor. The Shah had all the men shaved and the Muslim ambassador beheaded and sent his head back with the two remaining ambassadors.

Outraged, Genghis Khan organized one of his largest and most brutal invasion campaigns, fought by 200,000 soldiers in three divisions. He left a commander and troops in China, designated his successors to be his family members, and set out for Khwarazmia. Before he left, he divided his empire among his sons and immediate family and declared that his heir should be his charismatic third son, Ögedei. His invasion of Khwarazmia would last from 1219-1221 CE. His son Jochi led the first division into the northeast, and the second division under Jebe marched secretly to the southeast to form, with the first division, a pincer attack on Samarkand. The third division under Genghis Khan and Tolui moved in from the northwest. The Shah’s army, in contrast, was fragmented, a decisive factor in their defeat—the Mongols were not facing a unified defense.

The Mongol tactics were precise and often brutally efficient, including heavy cavalry, siege tactics, and even gunpowder weapons. The attack on the Khwarazm capital, Samarkand, was decisive and left the local population depleted and in tatters. Generally speaking, Mongol forces would enslave or massacre populations after a victorious capture of a city or region, establishing a new rule of law and highlighting Mongol dominance. Legend tells that the often flamboyant Genghis Khan executed the Khwarazm governor by pouring molten silver into his ears and eyes. Eventually the Shah fled rather than surrender, and he died shortly after, possibly killed by the Mongols. After their victory, Genghis Khan ordered two of his generals and their forces to completely destroy the remnants of the empire, including not only royal buildings but entire towns, populations, and even vast swaths of farmland.

The assault on the wealthy trading city of Urgench proved to be the most difficult battle of the Mongol invasion. Mongolian casualties were higher than normal because most battles they fought were in less densely packed urban settings. However, they were successful, and after an extensive invasion such as this one, young women and children were often given to the Mongol soldiers as slaves. Persian scholar Juvayni states that 50,000 Mongol soldiers were given the task of executing 24 Urgench citizens each. If Juvanyi’s estimation is true, 1.2 million people were killed, making it one of the bloodiest invasions in history.

During the invasion of Transoxania in 1219, along with the main Mongol force, Genghis Khan used a Chinese specialist catapult unit in battle, adding to the powerful tactics already in use by Mongol forces. They were used again in 1220 in Transoxania. The Chinese may have used these same catapults to hurl gunpowder bombs. In fact, historians have suggested that the Mongol invasion brought Chinese gunpowder weapons to Central Asia. One of these was the huochong, a Chinese mortar. By the time of Genghis Khan’s death in 1227, the Mongol Empire ruled from the Pacific Ocean to the Caspian Sea, an empire twice the size of the Roman Empire and Muslim Caliphate.

Pushing Farther West

The Mongols conquered the areas today known as Iran, Iraq, Syria, Caucasus and parts of Turkey. Further Mongol raids reached southwards as far as Gaza into the Palestine region in 1260 and 1300. The major battles were the Siege of Baghdad in 1258, when the Mongols sacked the city that for 500 years had been the center of Islamic power, and the Battle of Ain Jalut in 1260, when the Muslim Egyptians were for the first time able to stop the Mongol advance.

The Mongols were never able to expand farther west than the Middle East due to a combination of political and environmental factors, such as lack of sufficient grazing room for their horses.

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