The Decline of the Jin Dynasty

By the early 13th century, the once-mighty Jin Dynasty—founded by the Jurchen people in 1115 after overthrowing the Liao—had entered a period of irreversible decay. The empire’s third ruler, Emperor Xizong (完颜亶), was notorious for his alcoholism, erratic governance, and brutal purges of political rivals. His reign set the stage for instability when his cousin Wanyan Liang (完颜亮) assassinated him in a coup, only to prove an even more tyrannical ruler. Wanyan Liang’s disastrous war against the Southern Song Dynasty (1153) and subsequent assassination paved the way for Emperor Shizong (完颜雍), who earned the moniker “Little Yao and Shun” for his reforms. Yet these efforts were superficial; corruption, ethnic tensions, and military overextension festered beneath the surface.

The Jin’s weakening grasp did not go unnoticed. Among Genghis Khan’s inner circle was Yelü Ahai (耶律阿海), a former Jin official who defected after meeting the Mongol leader. His insider knowledge convinced Genghis that the Jin, despite their vast cities and armies, were vulnerable.

The Provocation at Jingzhou

In 1208, the Jin throne passed to Wanyan Yongji (完颜永济), an indecisive ruler whom Genghis Khan had previously dismissed as weak during a diplomatic meeting at Jingzhou. When Jin envoys demanded the traditional kowtow to the new emperor, Genghis Khan’s response became legendary: he spat on the ground and scoffed, “I thought the Central Plains’ emperor was divine, but this coward is unworthy of my bow!” The insult severed all pretense of loyalty.

The Road to War

### Intelligence and Alliances
Genghis Khan spent 1209–1211 preparing meticulously. He secured alliances with the Tangut-led Western Xia and the Uyghurs, isolating the Jin. Meanwhile, Yelü Ahai and Muslim traders provided critical intelligence: the Jin’s 3 million Jurchens ruled over 40 million Han Chinese, their armies were overstretched against the Southern Song, and their northern defenses relied on unreliable vassals like the Ongud tribe.

### The Kurultai Decision
At the 1211 kurultai (Mongol assembly), Genghis framed the war as both vengeance for ancestral grievances (the Jin’s “Reduction Policy” of culling Mongols) and opportunity. His speech swayed the nobles: “The Jin hoard gold, silks, and women. Why should we not take what they deny us?”

The Campaign Begins: Breaking the Wall

### The Fall of Wusha Fortress
Genghis’ forces crossed the Gobi in a decentralized, multi-pronged advance—a tactic that baffled Jin scouts. His general Muqali besieged the critical Wusha Fortress (乌沙堡) for months until a raid on its hidden supply depot, Wuyue Camp (乌月营), forced its surrender. The Mongols then used captured Jin soldiers as human shields, a psychological warfare tactic that shattered defender morale.

### The Battle of Yehuling
At Yehuling (野狐岭), a strategic pass, Jin commander Wanyan Chengyu (完颜承裕) made a fatal error: dispersing his troops along the Great Wall. Genghis concentrated his forces on the central command post, breaching the defenses in a single day. The rout continued at Huihechuan (浍河川), where the Jin’s last northern field army was annihilated.

Legacy: The Beginning of the End

The Yehuling campaign (1211–1212) marked a turning point in Eurasian history. Genghis Khan’s victory exposed the Jin’s fragility, emboldening rebellions among their Khitan and Han subjects. By 1215, Beijing fell, and the Mongols adopted siege engineers and defectors to dismantle the Jin’s urban strongholds. The war’s cultural impact was profound: it accelerated the Mongols’ transformation from steppe nomads into empire-builders and set the stage for their conquest of Eurasia.

The “spitting incident” thus became more than an insult—it was the spark that lit a fire consuming one dynasty and forging another. As Wanyan Chengyu lamented during his retreat: “Why did Heaven birth me only to birth Genghis Khan?” The answer, written in blood and conquest, reshaped the world.