Mongol Invasion of Khwarezmia - Initial Invasion

Initial Invasion

After compiling information from many intelligence sources, primarily from spies along the Silk Road, Genghis Khan carefully prepared his army, which was organized differently from Genghis' earlier campaigns. The changes had come in adding supporting units to his dreaded cavalry, both heavy and light. While still relying on the traditional advantages of his mobile nomadic cavalry, Genghis incorporated many aspects of warfare from China, particularly in siege warfare. His baggage train included such siege equipment as battering rams, gunpowder, trebuchets, and enormous siege bows capable of throwing 20-foot arrows into siege works. Also, the Mongol intelligence network was formidable. The Mongols never invaded an opponent whose military and economic will and ability to resist had not been thoroughly and completely scouted. For instance, Subutai and Batu Khan spent a year scouting central Europe, before destroying the armies of Hungary and Poland in two separate battles, two days apart.

The size of Genghis' army is often in dispute, ranging from a small army of 90,000 soldiers to a larger estimate of 250,000 soldiers, and Genghis brought along his most able generals to aid him. Genghis also brought a large body of foreigners with him, primarily of Chinese origin. These foreigners were siege experts, bridge-building experts, doctors and a variety of specialty soldiers.

During the invasion of Transoxania in 1219, along with the main Mongol force, Genghis Khan used a Chinese specialist catapult unit in battle; they were used again in 1220 in Transoxania. The Chinese may have used the catapults to hurl gunpowder bombs, since they already had them by this time While Genghis Khan was conquering Transoxania and Persia, several Chinese who were familiar with gunpowder were serving with Genghis's army. Historians have suggested that the Mongol invasion had brought Chinese gunpowder weapons to Central Asia. One of these was the huochong, a Chinese mortar.

In this invasion, the Khan first demonstrated the use of indirect attack that would become a hallmark of his later campaigns, and those of his sons and grandsons. The Khan divided his armies, and sent one force solely to find and execute the Shah - so that a ruler of an Empire as large as that of the Khan's, with a larger army, was forced to run for his life in his own country. The divided Mongol forces destroyed the Shah's forces piecemeal, and began the utter devastation of the country which would mark many of their later conquests.

The Shah's army, numbering roughly 400,000, was split among the various major cities. The Shah was fearful that his army, if placed in one large unit under a single command structure, might possibly be turned against him. Further, the Shah's reports from China indicated that the Mongols were not experts in siege warfare, and experienced problems when attempting to take fortified positions. The Shah's decisions on troop deployment would prove disastrous as the campaign unfolded.

Though tired from their journey, the Mongols still won their first victories against the Khwarezmian army. A Mongol army, under Jochi, with 25,000 to 30,000 men, attacked the Shah's army in southern Khwarezmia and prevented the much larger forces of the Shah from forcing them into the mountains. The primary Mongol army, headed personally by Genghis Khan, reached the city of Otrar in the fall of 1219. After besieging Otrar for five months, the Khan's forces managed to storm the main part of the city by entering a sally port gate that was not secured.

A further month went by before the citadel at Otrar was taken. Inalchuq held out until the end, even climbing to the top of the citadel in the last moments of the siege to throw down tiles at the oncoming Mongols. Genghis killed many of the inhabitants, enslaved the rest, and executed Inalchuq, possibly by pouring molten gold or silver down his throat as retribution for the capture of the Mongol caravan.