The Battle of Caishi is a major naval engagement of the Jin–Song wars that takes place on November 26–27, 1161.

Soldiers under the command of Prince Hailing, the Jurchen emperor of the Jin dynasty, try to cross the Yangtze River to attack Song China.

Yu Yunwen, a civil official, commands the defending Song army.

The paddlewheel warships of the Song fleet, equipped with trebuchets that launch incendiary bombs made of gunpowder and lime, decisively defeat the light ships of the Jin navy.Starting in 1125, the Jin had conquered all Song territories north of the Huai River.

In 1142, a peace treaty had settled the border between the two states, putting the Jin in control of northern China and the Song in control of the south.

Prince Hailing, enthroned in 1150, has been intent on uniting northern and southern China under a single emperor.

In 1158, he had asserted that the Song had violated the 1142 treaty, a pretext for declaring war on the Song; he had begun began preparations for the war in the following year, instituting a draft in which all able-bodied men are required to enlist.

The draft is unpopular, precipitating revolts that are later suppressed.

The Jin army leaves the capital of Kaifeng on October 15, 1161, and pushes through from the Huai to the Yangtze River without much resistance from the Song.The Song are fortified along the Yangtze front.

Hailing plans to cross the Yangtze at Caishi, south of modern-day Nanjing.

He embarks from the shore of the Yangtze on November 26, and clashes with Song forces led by Yu Yunwen in a naval engagement.

Hailing loses the battle and retreats to Yangzhou.

A military coup has taken place in the Jin court while Hailing is absent, enthroning Emperor Shizong as the new emperor.

Hailing is assassinated in a military camp by his own men shortly after the Caishi battle.

A peace treaty signed in 1165 endsthe conflict between Song and Jin.Song sources likely inflated the number of Jin soldiers and casualties that were present at Caishi, but the 18,000 figure for the Song army is plausible.

Modern studies suggest that the battle was smaller and that both sides were more evenly matched than traditional accounts suggest.

Nonetheless, the victory boosts the morale of the Song infantry and halts the southern advance of the Jin army.

Emperor Gaozong abdicates nine months after the battle ended.