Battle of Caishi (1161): Song Gunpowder Fleet Beats the Jin

The Battle of Caishi was fought on the Yangtze River on 26–27 November 1161, when a Southern Song force using paddle-wheel warships and gunpowder weapons stopped the Jin emperor Wanyan Liang from crossing the river. The victory, led by the civil official Yu Yunwen, ended the most dangerous Jin attempt to conquer southern China. It is also one of the earliest battles in which gunpowder weapons are clearly recorded at sea or on a river.

Background: Wanyan Liang’s ambition

After the Jingkang Incident of 1127 the Jurchen Jin ruled northern China, while the Southern Song held the south from its capital at Hangzhou. The peace treaty of 1141–1142, which followed the execution of the general Yue Fei, fixed the border on the Huai River.

In 1150 Wanyan Liang seized the Jin throne by murdering his cousin, Emperor Xizong. He admired Chinese culture and wanted to rule all of China as a single empire. He moved the Jin capital south, first to Zhongdu (Beijing) and in 1161 to Kaifeng, and prepared a massive invasion. Chinese sources speak of an army of 600,000; modern historians regard this as a propaganda figure, though the force was certainly very large.

The invasion

In the autumn of 1161 the Jin armies crossed the Huai River and advanced towards the Yangtze, the last great barrier before the Song heartland. The Song commander in the area, Wang Quan, retreated and was dismissed, leaving his troops without a leader near Caishi, a rocky point on the south bank of the river.

Yu Yunwen, a scholar-official sent to deliver rewards to the soldiers, arrived to find the army disorganised. Although he had no military rank, he took command, rallied around 18,000 men and prepared the river fleet.

The battle

When the Jin launched their boats across the Yangtze, the Song ships came out from behind an island and attacked. The Song fleet included paddle-wheel ships driven by men working treadles inside the hull, which could move swiftly without wind or oars. They rammed and sank many of the smaller Jin vessels, which had been hastily built or gathered for the crossing.

The Song also used gunpowder weapons. The poet and official Yang Wanli described “thunderclap bombs” of paper filled with lime and sulphur, launched by trebuchets; when they hit the water they burst and released blinding smoke and fire. These were incendiary and smoke weapons, part of the long development of the invention of gunpowder in China, rather than the high-explosive shells of later centuries.

The fighting lasted into a second day, when the Song attacked Jin boats at their landing place on the north bank. The Jin crossing failed with heavy losses, although the numbers of dead given by Song sources cannot be checked.

Why the Song won

The Yangtze at Caishi is wide, with strong currents, and crossing it under fire was extremely difficult. The Jin were a land power whose strength lay in cavalry, and their improvised boats were no match for purpose-built warships crewed by experienced river sailors. The Song, by contrast, had invested heavily in a river navy after 1127, recognising that the Yangtze was their main line of defence.

Morale also mattered. Yu Yunwen’s decision to stand and fight, rather than retreat as Wang Quan had done, steadied an army that might otherwise have dissolved. On the Jin side, many soldiers had been conscripted unwillingly, and news of the rebellion in the northeast spread doubt through the ranks. Later Chinese writers presented the battle as a triumph of the Confucian scholar over the barbarian invader, a picture that simplifies a contest decided above all by ships and logistics.

Aftermath

Wanyan Liang moved his army downstream towards Yangzhou to try again. But discontent in the Jin ranks was already severe, and in October 1161 a rival prince, Wanyan Yong, had been proclaimed emperor in Liaoyang in the northeast. In December 1161 Wanyan Liang was killed in his camp by his own officers. The Jin army withdrew, and Wanyan Yong reigned as Emperor Shizong.

In the same autumn a Song fleet also destroyed a Jin fleet at Tangdao, off the Shandong coast, ending the Jin plan to attack Hangzhou by sea. War continued for a few more years until the Peace of Longxing in 1165 restored a border similar to that of 1142.

Key people

• Yu Yunwen (1110–1174): the civil official who led the Song defence and later became chief councillor.
• Wanyan Liang (1122–1161): the Jin emperor, often called the Prince of Hailing, whose invasion failed.
• Wanyan Yong (1123–1189): the rival who became Emperor Shizong and made peace.

Timeline

• 1150: Wanyan Liang seizes the Jin throne.
• 1161, summer: The Jin court moves to Kaifeng to prepare the invasion.
• 1161, autumn: Jin armies cross the Huai; Wanyan Yong is proclaimed emperor in Liaoyang.
• 1161, 26–27 November: Battle of Caishi.
• 1161, December: Wanyan Liang is murdered by his officers.
• 1165: Peace of Longxing.

Why it matters

Caishi secured the Southern Song for another century and showed the value of naval power and gunpowder weapons on China’s great rivers. It also demonstrated that the Yangtze could be held, a lesson both sides remembered until the Mongol conquest.