Under his leadership, the armies of Mongolia first conquered the other steppe nomads. Thanks to their conquests, they became more powerful. In 1215, China was the first to be overthrown by Genghis Khan. Knowing that China would not welcome the presence of a powerful army on its borders, the Mongols decided to take the first step and take the battle to their doorstep. The conquered Chinese people paid tribute to the Mongols, bringing them increased wealth. The Mongols then transformed the rich city of Beijing into a prison. They also provided thousands of soldiers to fight in the Mongol armies. The Mongols also conquered much of Russian territory. Their conquests were rapid and brutal, often leaving behind thousands of dead.