The Maritime Alliance against Liao cost Song its empire in seven years

In 1120, Emperor Huizong of the Song dynasty entered into the Maritime Alliance (海上之盟) with the Jurchen-led Jin dynasty. The plan was straightforward: Song and Jin would attack the Liao dynasty from both sides, divide its territory, and end the Liao that had dominated northern China for two centuries. Song would at last recover the Sixteen Prefectures — the strategic border region lost since 938.

The plan unravelled immediately. The Song army, led by the eunuch general Tong Guan, was routed by the remnants of Liao's collapsing forces. The Jin army, meanwhile, swept through Liao's capitals with ease. Jin watched Song's performance and understood: this was a wealthy empire that could not fight. After Liao fell, Jin sold the Sixteen Prefectures to Song for 300,000 bolts of silk and 200,000 ounces of silver — a humiliating price for territory that was supposed to be won in battle.

The real blow came when Song accepted a Jin defector, Zhang Jue, breaking the alliance terms. Jin used this as a casus belli and invaded in 1125. By December 1126, 150,000 Jin troops surrounded Kaifeng — the largest city on earth, defended by a demoralised army and a panicked court. Emperor Qinzong had mishandled every negotiation and missed every military deadline. On 9 January 1127, Kaifeng fell.

What followed — the Jingkang Incident — was one of the epochal humiliations of Chinese history. Emperor Huizong and Emperor Qinzong were stripped of rank, demoted to commoners, and marched north in captivity. Over 14,000 members of the imperial family, officials, concubines, craftsmen, and scholars were taken to Jin territory. The imperial library, the bronze ritual vessels, the astronomical instruments — everything that represented Song civilisation — was carted away. The Northern Song dynasty, after 167 years, ceased to exist.