How did the Khitan people help Genghis Khan’s campaign against the Jin dynasty?

During the campaign against the Jin dynasty, the Khitan people provided critical support to Genghis Khan primarily by defecting from the Jin state.1

As the Jin dynasty faced internal instability and discontent among its non-Juchen populations, many Khitan nobles chose to defect to the Mongol side. These defectors served as valuable foreign advisers to Genghis Khan, offering essential knowledge regarding the territory, conditions, and military strategies of the Jin state. This assistance was particularly significant because the Mongols initially lacked experience in siege craft and warfare within densely populated areas, having previously relied primarily on cavalry tactics. By leveraging the expertise of these defectors, the Mongols were better equipped to navigate the challenges of conquering northern China.12