Mongol Siege of Kaifeng (1232-1233): Thunder Crash Bombs

The Mongol siege of Kaifeng in 1232-1233 was the decisive blow against the Jin dynasty, which had ruled northern China since the 12th century. Kaifeng’s defenders used some of the earliest documented gunpowder weapons, including iron “thunder crash bombs” and fire lances, while a devastating epidemic swept the crowded city. Kaifeng finally surrendered in 1233, and the Jin dynasty collapsed a year later.

Background

The Jin dynasty was founded by the Jurchen people in 1115 and had taken Kaifeng from the Song dynasty in 1127. From 1211 Genghis Khan attacked the Jin, and after the fall of their main capital, described in the article on the Mongol siege of Zhongdu, the Jin court moved south to Kaifeng in 1214. There it held out for almost two decades behind the Yellow River.

In 1230 Genghis Khan’s successor Ögedei renewed the war. His brother Tolui led an army through Song territory to outflank the Jin defences, and in early 1232 he destroyed the main Jin field army at the Battle of Sanfengshan. Kaifeng now lay open, and the Mongol general Subutai moved against it in the spring of 1232.

The siege and the gunpowder weapons

Kaifeng was one of the largest cities in the world, with long walls and a swollen population of refugees. Subutai’s forces surrounded it with earthworks and attacked with stone-throwing catapults. Many of their soldiers and engineers were Chinese, drafted from conquered territory.

The defenders answered with gunpowder weapons that the Jin, like the Song, had developed over the previous century. The History of Jin, compiled in 1344, describes the zhentianlei, or “thunder crash bomb”: a gunpowder charge in an iron casing. According to the account, bombs were lowered on iron chains onto Mongol sappers digging at the foot of the walls, blowing apart the cowhide shelters that protected them. The noise was said to be heard many kilometres away. The defenders also used the feihuoqiang, or “flying fire lance”, a tube of gunpowder fixed to a spear that shot flame several metres. Joseph Needham and later historians treat these weapons as an important stage in the development of firearms.

Epidemic and surrender

In the summer of 1232 a terrible epidemic broke out in the besieged city. The History of Jin claims that around 900,000 coffins or bodies were carried out through the gates in about fifty days; modern historians regard this number as exaggerated, but there is no doubt that a large part of the population died. The physician Li Gao, who lived in Kaifeng at the time, later wrote about the illness, though its exact nature is uncertain.

At the end of 1232 Emperor Aizong left Kaifeng in an attempt to raise new forces, fleeing first to Guide and then to Caizhou. In 1233 the commander left in charge, Cui Li, killed rival officials and surrendered the city to Subutai. Subutai wished to massacre the inhabitants, as was Mongol practice with cities that had resisted. According to the sources, the Khitan minister Yelü Chucai persuaded Ögedei that skilled craftsmen and taxpayers were worth more alive, and the population was spared. Members of the Jin imperial clan who had stayed behind were taken away and killed.

Consequences

The Jin dynasty survived only a few months longer. The Song dynasty in the south allied with the Mongols, and their combined armies besieged Caizhou. The city fell in early 1234; Aizong took his own life and his successor died in the fighting. The alliance soon broke down, and in 1234 a Song attempt to reoccupy Kaifeng and Luoyang began the long war between the Mongols and the Song, which lasted until the siege of Xiangyang and beyond.

Kaifeng never regained its former importance. The siege also showed the Mongols the value of gunpowder and Chinese engineers, whom they later employed in campaigns as far away as the Middle East.

Key people

• Subutai (c. 1175-1248): Mongol general who directed the siege and later the western campaign into Europe.
• Ögedei Khan (r. 1229-1241): Great Khan who renewed the war against the Jin.
• Emperor Aizong of Jin (r. 1224-1234): last effective Jin emperor, who left Kaifeng and died at Caizhou.
• Cui Li: Jin commander who seized power in the city and surrendered it in 1233.
• Yelü Chucai (1190-1244): Khitan adviser to Ögedei, credited with saving the city’s population.

Timeline

• 1214: The Jin court moves from Zhongdu to Kaifeng.
• 1232, February: Tolui defeats the Jin army at Sanfengshan.
• 1232, spring: Subutai begins the siege of Kaifeng.
• 1232, summer: An epidemic kills a large share of the city’s population.
• 1232, end of year: Emperor Aizong leaves Kaifeng.
• 1233, May: Cui Li surrenders Kaifeng to the Mongols.
• 1234, February: Caizhou falls to Mongol and Song forces; the Jin dynasty ends.

Why it matters

The fall of Kaifeng marked the end of the Jin dynasty and brought all of northern China under Mongol rule. It is also one of the best-documented early uses of explosive gunpowder weapons in war, a key step in the military technology that later spread across Eurasia.