Map Introduction

I. Tribal Landscape of the Mongolian Plateau and the Oppression of the Jin Dynasty

By the late 12th century, the Mongolian Plateau was divided among tribes such as the Mongols, Kereyid, Tatar, Merkit, and Naiman, with the Kereyid (ruled by Ong Khan) and the Mongols (the clan of Temüjin) being the most powerful. To maintain control over the steppe, the Jin Dynasty pursued a "divide and rule" policy, weakening the Mongols through measures like the "Reducing the Able-bodied" (periodic massacres of Mongol men every three years) and instigating inter-tribal warfare. Ambaghai Khan, an ancestor of Genghis Khan (Temüjin), was executed by the Jin using the cruel "wooden donkey" torture, sowing deep-seated hatred.

II. Mongol Unification and the Downfall of the Kereyid

In 1206, Temüjin established the Great Mongol State at the Kurultai (assembly) on the Onon River, integrating military and civilian forces using the thousand-household system. His primary objective was the destruction of the rival Kereyid: In 1203, exploiting the suspicion between Ong Khan and his son Senggum, Temüjin crushed the main Kereyid forces at the Battle of Qalqaljid Sands and subsequently captured their capital at Orqo. Ong Khan fled and was killed. This victory granted the Mongols the fertile eastern pastures of the steppe, laying the foundation for future conquests.

III. Mongol Southern Invasion and the Collapse of the Jin Dynasty

At the Battle of Wild Fox Ridge in 1211, a Mongol force of 100,000 annihilated a 450,000-strong Jin main army. After Emperor Xuanzong of Jin moved his capital south to Bianjing (Kaifeng), the Mongols gradually encroached upon North China, culminating in the fall of the Jin Dynasty at the Battle of Caizhou in 1234. Although the Southern Song had allied with the Mongols to destroy the Jin, the Mongols soon turned their armies southward against the Song, creating a situation where "when the lips [the Jin] are gone, the teeth [the Song] are exposed to the cold."

IV. Tribal Integration and the Military System

The Mongols incorporated conquered tribes like the Kereyid and Tatar into the "thousand-household" system, preserving their social organization while stripping them of independence. Kereyid warriors became a significant component of the Mongol cavalry. Their nomadic tactics, combined with Mongol mobility, created a "blitzkrieg" advantage.

V. Historical Impact

The rise of the Mongols ended the Jin-Song stalemate. Their model of tribal integration laid the groundwork for the multi-ethnic Yuan Dynasty. The disappearance of tribes like the Kereyid marked the end of the traditional steppe tribal confederation system, replaced by a centralized military empire.