 Before the rule of Kublai Khan, the Mongols had launched military campaigns as far as Eastern Europe, and had conquered Russia, Siberia, Tibet, Korea, North China, Yunnan, Iraq, Anatolia and Iran.However, the Song dynasty was difficult to conquer because of the strategic location of Xiangyang, which became a vital position for Kublai to capture and hold.The city guarded the waterways of South China because the Han River was a major tributary into the Yangtze River.