Battle of Yehuling

In 1206, Temüjin had united all the tribes on the Mongolian Plateau under his rule and received the title "Genghis Khan". The Jurchen-led Jin dynasty in northern China became a major obstacle to the Mongol Empire's quest for world domination. In the past, the Jin dynasty had adopted a divide-and-rule strategy to break up the various Mongol tribes and keep them under control. However, after realising that this strategy no longer worked, they began to actively prepare for war with the aim of eliminating the Mongol threat in a single campaign. Starting in the reign of Emperor Zhangzong, the Jin dynasty had constructed a line of structural defences about 300 kilometres long along its northern border; this line is sometimes loosely referred to as the "Jin dynasty's Great Wall".

Earlier in 1204, Genghis Khan had subdued the Ongud, a Mongol tribe helping the Jin dynasty guard its northern border. At the same time, Genghis Khan also formed an alliance with the Ongud by marrying his daughter to the Ongud chief's son. The Mongols controlled the area north of the Yin Mountains and started stockpiling resources in preparation for a military campaign against the Jin dynasty. Moreover, the Mongols had also been actively luring and inducing some Jurchens to defect or surrender. The Jin emperor Xingsheng underestimated the Mongol threat and had been gradually neglecting the defences against the Mongols. He was also delusional in his belief that the Jin dynasty was far more powerful than the Mongols.

In 1210, Genghis Khan insulted Emperor Xingsheng of the Jin by publicly stating that he was cowardly and unfit to be a leader. He also added, "The emperor should be a man from the sky like me." When the Jin emperor received news of this, he was so enraged that he executed the Mongol ambassador. Tensions between the Mongols and Jin dynasty started to escalate. In March 1211, the Mongols rallied 100,000 troops for a campaign against the Jin dynasty, leaving behind only about 2,000 men to guard their base in Mongolia. This meant that well over 90% of the Mongol forces had been mobilized for the campaign. Before embarking, Genghis Khan prayed to the sky deity Tengri along the Kherlen River to bless the Mongols with victory, and made a symbolic vow to avenge his ancestor, Ambaghai, who was executed by crucifixion in 1146 at the order of Emperor Xizong of the Jin dynasty.

The Mongol horse army led by Genghis Khan, with their preparations for war now complete, sped out towards the Great Wall by late March 1211, which was the border between the Mongol Empire and Jin China, finally beginning the Mongol war of conquest against the Jin. The Great Wall, backed up with numerous castles and towers, was defended by nearly a million Jin imperial soldiers which was composed of 800,000 infantry and 150,000 elite cavalry[2] whom Emperor Xingsheng earlier sent as a defensive measure to counter the Mongol threat. The Jin general Wanyan Chenyu, sent by the Jin emperor under direct orders to stop and if possible crush the Mongol incursion, was the one leading the Jin army in the Great Wall.

Although the Jin imperial army outnumbered the invading Mongol forces nearly ten times its own, Wanyan Chenyu ordered them to be spread out throughout the Wall in an attempt to block the Mongol approach, meaning in any one place several sections and ramparts of the wall have only a few defenders on them. The Wall itself is not a continuous defensive wall but a system of fortifications with many walls not connected towards each other but are supported and reinforced by castles and fortresses. This is a fact that Genghis Khan recognized, having his scouts keep watch on much of the Wall before he could engage his forces. Having gained intelligence from his scouts, he thus recognized that the least defended portion of the Wall's defensive system was at the Wusha Fortress, which leads to a desert ridge called Yehuling, inhabited by wild foxes hence the name of the area which in Chinese literally means the "Wild Fox Ridge". The ridge of Yehuling is northwest of the Juyong Pass, which was the gateway towards the Jin capital of Zhongdu (中都, lit. "central capital"; present-day Beijing); it was also at the plain at the foot of the ridge that the main force of the Jin army, numbering 400,000 troops,[4] was also encamped.

The battle was fought in three stages between March and October 1211, as soon as the Mongol army went past through the Great Wall with little opposition.

After the battle, Emperor Xingsheng of the Jin was assassinated in the central capital, Zhongdu (中都; present-day Beijing), by one of his generals, Hushahu (胡沙虎), who then took control of the city. The Mongols pressed on and besieged Zhongdu for about four years. During the siege, the residents of Zhongdu were forced to resort to cannibalism to survive, before they finally decided to surrender. The Mongols allowed the Jin dynasty to retain control of Zhongdu but forced them to pay a tribute of 500 men, 500 women, and 3,000 horses. In the summer of 1212, Emperor Xuanzong of the Jin dynasty abandoned Zhongdu and relocated the capital to Bianjing (present-day Kaifeng, Henan) in the south. This display of weakness and fear only encouraged the Mongols to continue their attack to conquer the rest of Jin.

The forces of the Jin dynasty were defeated in detail in the Yehuling Campaign.[2] Roughly ten Jin cities were plundered by the Mongols. While the Jin dynasty managed to retain power for the next two decades or so, its core was severely weakened. In spite of the defeat, the Jin dynasty prioritised conquering the Southern Song dynasty in southern China over defending its borders against future Mongol incursions and invasions. This led to increasing enmity between the Southern Song dynasty and the Jin dynasty. Eventually, the Southern Song dynasty allied with the Mongols against the Jin dynasty and destroyed the latter in 1234.[5]