Battle of the Badger Mouth The Battle of the Badger Mouth ( 獾兒嘴及野狐嶺戰役 , simplified 獾儿嘴及野狐岭战役 , the Campaign of the Badger Mouth and Wild Fox Peak ) was the major decisive battle in the first stage of the Mongol – Jin War . Background . In 1210 , Genghis Khan insulted Emperor Weishaowang by publicly stating that he was a coward and unfit to be a leader . Genghis added , " The emperor should be a man from sky like me . " Soon , news spread to the Jin emperor through a Jin officer . The Jin emperor was enraged and ordered the execution of the Mongolian ambassador . Tensions between the Jin and the Mongols started to escalate and Genghis Khan declared war with the Jin . The Mongolian army amassed 90 , 000 men for the offensive force in the expedition against the emperor in March 1211 . Genghis Khan only maintained a defending force of 2 , 000 guards in Mongolia . This means that well over 90 % of the available forces in Mongolia at the time were mobilized for this campaign . Before the expedition , Genghis Khan conducted a religious ritual with his troops by praying to Tengri along the Kherlen River for victory and made a vow to avenge his ambassador , Ambaghai Khan , who was betrayed by the Tartar and executed by the Jin court . Jin ' s army . Jin ' s army included : 1 . Border troops : recently defeated by Mongolia at the Battle of Wushabao several months before the campaign , the border troops had withdrawn to Badger Mouth . Their total strength amounted to 100 , 000 and were led by 1st Prime Minister Du Qiannu . 2 . Main troops : their strength amounted to 250 , 000 and chief commander of the army was field marshal Wanyan Chenyu , 2nd Prime Minister and general Ming An . Most of the troops hailed from the capital . 3 . Reinforcement troops : emergency troops from all corners of Jin country , their strength amounted to 150 , 000 and the commander was vice field marshal Hersle Whosawho , an ambitious man . He was to defend Datong with his reinforcements . Battles . This campaign included a series of five battles that took place from May to October , 1211 : 1 . Battle of Wushabao ( 烏沙堡戰役 ) : May – June . 2 . Battle of Datong ( 大同攻防戰 ) : lasted seven days in August . Genghis Khan ordered his three elder sons and general Yelü Tuhwa into battle . Each of his sons commanded 10 , 000 cavalry . A total of 30 , 000 cavalry besieged the city in order to cover the side line of the Genghis Khan ' s troops and cut off Jin ' s reinforcements to capital . 3 . Badger Mouth Campaign ( 獾兒嘴及野狐嶺戰役 ) : occurred in August . This pass leads directly to Jin ' s capital and was attacked by Genghis Khan with a commanding force of 60 , 000 . 4 . Battle of Guihebao ( 澮河堡戰役 ) : happened in October and the combat lasted three days . 5 . The Mongol occupation of Juyongguan : Jin ' s 3rd Prime Minister Tu Danyi ( 徒單鎰 ) successfully defended the capital with a commanding force of 20 , 000 , signalling the end of the campaign . Battle of Wushabao . Wushabao is located at the present city of Ulanqab . Through the years , Jin ' s 1st Prime Minister Dujis Qiannu ordered the construction line of a series of single fortifications to oversee the Mongols , but this tactic turns out to be faulty , even though they maintain their stability on the border . Wushabao was one of the largest and most important fortresses at the time . Jebe attacked Wushabao and achieved no success . He changed his tactics by attacking Wushabao ' s reinforcement base . With the fall of the base , Jebe manage to capture Wushabao . Hearing the news , a senior official of Jin ( a rank below prime minister ) led the troops into retreat from the neighboring three counties to Badger Mouth . The retreat provided a golden opportunity for Jebe and soon the three counties were captured with ease . Battle of the Badger Mouth . To combat the Mongol advance , the Jin had withdrawn soldiers from cities for hundreds of miles , resulting in a combined force of approximately 400 , 000 to 500 , 000 soldiers being stationed at Badger Mouth . However , the Jin were overly confident in the defensive position of the pass ; Genghis eventually circumvented Jin defenses by sending his men over the peaks surrounding the pass , allowing him to encircle the much larger Jin army . As Genghis attacked the front of the Jin army at the entrance to the pass , his forces simultaneously routed the Jin cavalry from behind . The encircling force then proceeded to attack the supply camps in the rear of the Jin army , resulting in the slaughter of many resting Jin soldiers . When Jin forces in the front lines of the battle were eventually pushed into retreat by the bulk of the Mongol army , the subsequent chaos resulted in the slaughter of even more Jin soldiers . Following the battle , the general of the Jin army retreated to the central Jin capital of Zhongdu ( modern day Beijing ) and assassinated the emperor , assuming control of the city . After a four - year Mongol siege , which saw the residents of Beijing reduced to cannibalism in order to survive , the city finally surrendered . The Jin were allowed to retain control of Zhongdu , but were forced to pay a large tribute in return . The following summer , Jin Emperor Xuānzōng ( 宣宗 ) abandoned Zhongdu and moved the government to the " southern capital " of Kaifeng . While the Jin maintained a grasp on power for several more years , the empire was severely weakened , and eventually capitulated to a combined Mongol and Song force in 1234 . Aftermath . After this battle and campaign , the Jin dynasty lost half of its 950 , 000 troops . Roughly ten Jin cities were plundered by the Mongols and Genghis Khan ordered a tribute of 500 males , 500 virgins and 3000 horses to be taken back to the Mongolian plains . In spite of the defeat , Jin prioritized conquering the Song dynasty over defending its borders against future Mongol incursions and invasions .