A lesser man might have been content just to rule China. But Genghis Khan's desire for land and power was seemingly insatiable.
In 1219, the Mongol ruler went to war against the Khwarezm Empire, which sprawled over an expanse of central Asia that included Turkmenistan, Uzbekistan, Afghanistan and Iran. Its ruler, Shah Muhammad, had made the mistake of killing a Mongol ambassador and a trading caravan, perhaps assuming that his walled capital of Samarkand would deter the Mongols. But the Shah's forces were no match for the Mongols, who took the city and burned alive about 1,000 of the Shah's soldiers who had taken refuge in a mosque. Then they leveled the city, killing 100,000 people. They spared 30,000 men with skills — craftsmen, doctors and scribes — who were taken as captives to work in Mongolia [source: Edwards].
Genghis Khan's forces continued to advance, taking more and more territory. Eventually, they reached the edge of Europe. But keeping the vast realm under Mongol control wasn't easy. In the mid-1220s, the Tangut people in Xi Xia, Genghis Khan's first big conquest, rebelled against him, so he turned back east to attack them once again.
But while he was in Xi Xia, Genghis Khan's health mysteriously failed. By one account, he was injured in a fall from his horse while on a hunt, while another account describes him as becoming ill, perhaps from typhus. In August of 1227, on his deathbed, he ordered the extermination of the Tanguts, appointed his son Ogodei as his successor, and then died [source: Edwards]. He probably was 65 years old.