Having united the steppe tribes, Genghis Khan ruled over some 1 million people. In order to suppress the traditional causes of tribal warfare, he abolished inherited aristocratic titles. He also forbade the selling and kidnapping of women, banned the enslavement of any Mongol and made livestock theft punishable by death. Moreover, Genghis Khan ordered the adoption of a writing system, conducted a regular census, granted diplomatic immunity to foreign ambassadors and allowed freedom of religion well before that idea caught on elsewhere.
Genghis Khan’s first campaign outside of Mongolia took place against the Xi Xia kingdom of northwestern China. After a series of raids, the Mongols launched a major initiative in 1209 that brought them to the doorstep of Yinchuan, the Xi Xia capital. Unlike other armies, the Mongols traveled with no supply train other than a large reserve of horses. The army consisted almost entirely of cavalrymen, who were expert riders and deadly with a bow and arrows. At Yinchuan, the Mongols deployed a false withdrawal—one of their signature tactics—and then initiated a siege. Though their attempt to flood the city failed, the Xi Xia ruler submitted and presented tribute.
The Mongols next attacked the Jin Dynasty of northern China, whose ruler had made the mistake of demanding Genghis Khan’s submission. From 1211 to 1214, the outnumbered Mongols ravaged the countryside and sent refugees pouring into the cities. Food shortages became a problem, and the Jin army ended up killing tens of thousands of its own peasants. In 1214 the Mongols besieged the capital of Zhongdu (now Beijing), and the Jin ruler agreed to hand over large amounts of silk, silver, gold and horses. When the Jin ruler subsequently moved his court south to the city of Kaifeng, Genghis Khan took this as a breach of their agreement and, with the help of Jin deserters, sacked Zhongdu to the ground.
In 1219 Genghis Khan went to war against the Khwarezm Empire in present-day Turkmenistan, Uzbekistan, Afghanistan and Iran. The sultan there had agreed to a trade treaty, but when the first caravan arrived its goods were stolen and its merchants were killed. The sultan then murdered some of Genghis Khan’s ambassadors. Despite once again being outnumbered, the Mongol horde swept through one Khwarezm city after another, including Bukhara, Samarkand and Urgench. Skilled workers such as carpenters and jewelers were usually saved, while aristocrats and resisting soldiers were killed. Unskilled workers, meanwhile, were often used as human shields during the next assault. No one knows with any certainty how many people died during Genghis Khan’s wars, in part because the Mongols propagated their vicious image as a way of spreading terror.