A Kingdom Between Two Threats: Southern Song’s Precarious Position

In the early 13th century, the Southern Song dynasty found itself caught between two formidable powers: the declining Jin dynasty to the north and the rapidly expanding Mongol Empire. This geopolitical tension came to a head when a Jin envoy named Wanyan Ahu arrived in Hangzhou, the Southern Song capital, with a desperate plea for grain supplies. His message carried a stark warning: “The Mongols have destroyed forty nations, including Western Xia. After Xia fell to them, they came for us (Jin). When we fall, Southern Song will be next.”

The envoy invoked the ancient Chinese proverb “If the lips are gone, the teeth will be cold” (唇亡齿寒) – a phrase appearing in classics like the Zuo Zhuan and Mozi that warned of interdependence between neighbors. Yet this appeal to shared destiny rang hollow after a century of hostility. The Jin had long demanded tribute from Southern Song while launching periodic southern invasions. To the Song court, the Jin remained the enemy that had seized half their territory during the Jingkang Incident of 1127, when Emperor Huizong and Qinzong were captured in the fall of Kaifeng.

The Temptation of Revenge: Southern Song Aligns With the Mongols

Southern Song leaders saw the Mongol-Jin conflict as a golden opportunity to reclaim lost lands. Unlike their bitter history with the Jin, the Song had no prior conflicts with the Mongols. When the Mongols proposed a joint campaign against the Jin, the offer proved irresistible.

In 1234, Southern Song general Meng Gong led 20,000 troops northward with 300,000 dan of grain – provisions the Mongols welcomed more than the military support. The combined forces besieged Caizhou, the last refuge of Jin Emperor Aizong. When the city fell and the emperor committed suicide, the 120-year-old Jin dynasty collapsed. Southern Song officials celebrated this as vengeance for the humiliations of 1127.

The Illusion of Restoration: Southern Song’s Strategic Blunders

Flush with victory, Southern Song leaders began planning the “recovery” of former territories like Kaifeng and Luoyang. Emperor Lizong ordered ceremonial visits to ancestral tombs neglected for over a century. However, critical divisions emerged in the court:

– The Hawkish Faction (led by Zhao Fan and Zhao Kui) argued that marching into former Song lands required no Mongol permission. They dismissed the Mongols as “barbarians” beneath diplomatic engagement.
– The Pragmatic Faction (led by Shi Songzhi) cautioned that occupying cities recently taken by Mongol forces without negotiation would provoke retaliation.

Ignoring these warnings, Southern Song mobilized 200,000 troops for a northern expedition. Their entry into Kaifeng proved bloodless – the unpopular Jin turncoat Cui Li had already been overthrown. But when forces advanced toward Luoyang, they found a devastated landscape with only 300 households remaining.

Collapse of an Alliance: How Arrogance Led to Disaster

Southern Song’s occupation quickly unraveled due to fatal miscalculations:

1. Logistical Failure: The army had rushed north expecting local support, but war-weary peasants, resentful of Song officials who had abandoned them a century earlier, refused provisions.
2. Cultural Arrogance: The hawks’ dismissive attitude toward the Mongols as “uncivilized barbarians” blinded them to Mongol military capabilities and territorial claims.
3. Diplomatic Neglect: No agreements clarified post-Jin territorial arrangements. The Mongols viewed Song troop movements as treaty violations.

Within months, Mongol cavalry swept from Tong Pass, crushing the underfed Song forces. The alliance that had destroyed Jin now lay in ruins – a collapse historian later condemned as stemming from “the stratagems of impulsive women” (妇人之谋), reflecting contemporary gender biases in their critique of reckless decision-making.

Legacy: The Fatal Prelude to Mongol Conquest

The failed northern expedition had catastrophic consequences:
– It provided the Mongols justification for invading Southern Song, culminating in the 1279 fall of Song at the Battle of Yamen.
– Exposed flaws in Southern Song’s strategic culture: overreliance on historical claims, underestimation of nomadic powers, and factional divides.
– Demonstrated how the “barbarian” stereotype blinded Chinese states to evolving geopolitical realities.

The 1234-35 debacle marked a pivotal transition – the moment Southern Song traded one existential threat (Jin) for another far more dangerous (Mongols). Its mishandling of the “lips and teeth” warning became a cautionary tale about the perils of letting historical grievances override strategic pragmatism.