Genghis Khan was declared
Khaghan in 1206. The Mongols had united under his leadership, and defeated the rival tribes of the steppes. In the same period,
China proper was divided into three separate dynastic states. In the north, the Jurchen-led Jin dynasty controlled
Manchuria and all of China proper north of the
Huai River. The
Tangut-led
Western Xia dynasty ruled parts of the western China, while the
Song dynasty reigned over the
south. The Mongols subjugated Western Xia in 1210. In that same year, the Mongols renounced their
vassalage to the Jin. Hostilities between the Jin and Mongols had been building up. The Mongols coveted the prosperity of Jin territory. They may have also harbored a grudge against the Jin for assassinating
Ambaghai, one of Genghis' predecessors, and for the Jin emperor
Wanyan Yongji's rude behavior to Genghis Khan when Wanyan Yongji was still a Jurchen prince. The Mongols learned that a famine had struck the Jin, and invaded in 1211. Two armies were dispatched by the Mongols into Jin territory, with one under the command of Genghis himself. The Jin built up its armies and reinforced its cities in preparation for the Mongol incursion. The Mongol strategy was based on capturing small settlements and ignoring the fortifications of major cities. They looted the land and retreated in 1212. The Mongols returned the next year and besieged
Zhongdu, the capital of the Jin, in 1213. The Mongols were not able to penetrate the walls of the city in the
Battle of Zhongdu, but intimidated the Jin emperor into paying
tribute. They withdrew in 1214. Later in the year, fearing another siege, the Jin moved their capital from Zhongdu to Kaifeng. The Mongols besieged Zhongdu once more in 1215 once they learned that the Jin court had fled from the city. The city fell on May 31, and by 1216, large swaths of Jin territory were under Mongol control. Meanwhile, the Jin had been afflicted by multiple revolts. In Manchuria, the Khitans, under the leadership of
Yelü Liuge, declared their independence from the Jin and allied with the Mongols. Yelü was enthroned a
puppet ruler subordinate to the Mongols in 1213, and given the title emperor of the
Liao dynasty. The Jurchen expedition sent against him commanded by
Puxian Wannu was not successful. Wannu, realizing the Jin dynasty was on the verge of collapse, rebelled and declared himself king of
Eastern Xia in 1215. Further south, rebellions had broken out in Shandong beginning with Yang Anguo's revolt in 1214. The rebels were known as
Red Coats, from the color of the uniforms they wore starting in 1215. After the fall of Zhongdu in 1215, the Mongols downsized their war effort against the Jin, and shifted their resources in preparation for the invasion of Central Asia. The Jin tried to make up for their territorial losses to the Mongols by invading the Song in 1217. The invasion was fruitless, so the Jin wanted to negotiate for peace, but the Song rebuffed the offers. By 1218, Jurchen diplomats were prohibited from traveling to the Song. The Mongol war against the Jin had subsided, but not stopped, and went on through the early 1220s under the command of the general
Muqali. Muqali died from sickness in 1223, and the Mongol campaigns against the Jin wound down. The Jin settled for peace with the Song, but the Song continued to assist the Red Coats insurgency against the Jin. Genghis Khan fell ill and died in 1227. Ögedei was his successor, and he renewed the war against the Jin in 1230. The ethnic
Han general
Shi Tianze led troops to pursue Emperor Aizong as he retreated and destroyed an 80,000-strong Jin army led by Wanyan Chengyi (完顏承裔) at Pucheng (蒲城). Shi Tianze led a Han Tumen in the Mongol army since his family under his father Shi Bingzhi defected to the Mongols under Muqali against the Jin. ==Siege of Kaifeng==