section_path: Later reign: western expansion and return to China (1216–1227)/Invasion of the Khwarazmian Empire (1219–1221)
section_name: Invasion of the Khwarazmian Empire (1219–1221)
paragraph_text: Invasion of the Khwarazmian Empire (1219–1221)
  
  Genghis had now attained complete control of the eastern portion of the Silk Road, and his territory bordered that of the Khwarazmian Empire, which ruled over much of Central Asia, Persia and Afghanistan. Merchants from both sides were eager to restart trading, which had halted during Kuchlug's rule; the Khwarazmian ruler Muhammad II dispatched an envoy shortly after the Mongol capture of Zhongdu, while Genghis instructed his merchants to obtain the high-quality textiles and steel of Central and Western Asia. Many members of the altan uruq invested in one particular caravan of 450 merchants which set off to Khwarazmia in 1218 with a large quantity of wares. Inalchuq, the governor of the Khwarazmian border town of Otrar, decided to massacre the merchants on grounds of espionage and seize the goods; Muhammad had grown suspicious of Genghis's intentions and either supported Inalchuq or turned a blind eye. A Mongol ambassador was sent with two companions to avert war, but Muhammad killed him and humiliated his companions. The killing of an envoy infuriated Genghis, who resolved to leave Muqali with a small force in North China and invade Khwarazmia with most of his army.
  
  Muhammad's empire was large but disunited: he ruled alongside his mother Terken Khatun in what the historian Peter Golden terms "an uneasy diarchy", while the Khwarazmian nobility and populace were discontented with his warring and the centralisation of government. For these reasons and others he declined to meet the Mongols in the field, instead garrisoning his unruly troops in his major cities. This allowed the lightly armoured, highly mobile Mongol armies uncontested superiority outside city walls. Otrar was besieged in autumn 1219—the siege dragged on for five months, but in February 1220 the city fell and Inalchuq was executed. Genghis had meanwhile divided his forces. Leaving his sons Chagatai and Ögedei to besiege the city, he had sent Jochi northwards down the Syr Darya river and another force southwards into central Transoxiana, while he and Tolui took the main Mongol army across the Kyzylkum Desert, surprising the garrison of Bukhara in a pincer movement.
  
  Bukhara's citadel was captured in February 1220 and Genghis moved against Muhammad's residence Samarkand, which fell the following month. Bewildered by the speed of the Mongol conquests, Muhammad fled from Balkh, closely followed by Jebe and Subutai; the two generals pursued the Khwarazmshah until he died from dysentry on a Caspian Sea island in winter 1220–21, having nominated his eldest son Jalal al-Din as his successor. Jebe and Subutai then set out on a 7,500-kilometre (4,700 mi) -expedition around the Caspian Sea. Later called the Great Raid, this lasted four years and saw the Mongols come into contact with Europe for the first time. Meanwhile, the Khwarazmian capital of Gurganj was being besieged by Genghis's three eldest sons. The long siege ended in spring 1221 amid brutal urban conflict. Jalal al-Din moved southwards to Afghanistan, gathering forces on the way and defeating a Mongol unit under the command of Shigi Qutuqu, Genghis's adopted son, in the Battle of Parwan. Jalal was weakened by arguments among his commanders, and after losing decisively at the Battle of the Indus in November 1221, he was compelled to escape across the Indus river into India.
  
  Genghis's youngest son Tolui was concurrently conducting a brutal campaign in the regions of Khorasan. Every city that resisted was destroyed— Nishapur, Merv and Herat, three of the largest and wealthiest cities in the world, were all annihilated. This campaign established Genghis's lasting image as a ruthless, inhumane conqueror. Contemporary Persian historians placed the death toll from the three sieges alone at over 5.7 million—a number regarded as grossly exaggerated by modern scholars. Nevertheless, even a total death toll of 1.25 million for the entire campaign, as estimated by John Man, would have been a demographic catastrophe.