The Battle of Caishi (Chinese: 采石之戰) was a major naval engagement of the Jin–Song Wars of China that took place on November 26–27, 1161.

The paddle-wheel warships of the Song fleet, equipped with trebuchets that launched incendiary bombs made of gunpowder and lime, decisively defeated the light ships of the Jin navy.

Wanyan Liang planned to cross the river at Caishi (modern day Ma'anshan), south of modern-day Nanjing.

He embarked from the shore of the Yangzi on November 26, and clashed with Song forces led by Yu Yunwen and Chen Kangbo in a naval engagement.

However, in 1114, the Jurchen, unified under the rule of Wanyan Aguda, plotted a revolt against their former overlords: the Khitan-led Liao dynasty.

[7] Negotiations between the Song and Jin produced a treaty in 1123, but bilateral relations deteriorated because of territorial disputes over the Sixteen Prefectures.

[24] Wanyan Liang considered himself more of a Han authoritarian emperor than a Jurchen leader who ruled through a tribal council.

[25] The History of Jin contends that Wanyan Liang told his officials that the three desires of his life were conquest, absolute power, and women.

[31] The execution of 130 members of the two royal clans in the span of a few months proved unpopular, and the Khitans soon revolted in Northeast China.

[31] They refused to be drafted into the army, maintaining that conscription would leave their homeland unprotected from rival tribes on the steppes.

[31] Some Song officials foresaw the impending war,[31] but Emperor Gaozong hoped to maintain peaceful relations with the Jin.

The paddle-wheel warships of the Song fleet, equipped with trebuchets that launched incendiary bombs made of gunpowder and lime, decisively defeated the light ships of the Jin navy.

Chen led a naval regiment of his own, dispatching general Yu Yunwen (a scholar-official), his lieutenants Dai Gao, Jian Kang, Shi Zhun, and others to lead the rest of the army.

[33] Yu, who was a Drafting Official of the Secretariat (Chinese: 中書舍人; pinyin: zhongshu sheren), was at Caishi to distribute awards to Song soldiers who had been selected for their outstanding service.

[37] One account of the war contends that the Jin ships were constructed in a week with materials recycled from destroyed buildings.

The shortage of vessels and the poor quality of those available prevented the Jin from ferrying more soldiers needed for fighting a naval battle with the Song.

[39] The Jin soldiers who managed to cross the river and reach the shore were assaulted by Song troops waiting on the other side.

Your minister walk[ed] back and forth in our ranks, again and again exhorted our men about their great duty and also promising them rewards.

The desertions and casualties from suppressing revolts while advancing southward would have shrunk that number by the time the Jin reached the Yangzi.

[34] An account of the battle by a different Song source holds that 24,000 Jin soldiers died and that 500 combatants and five meng-an were taken as prisoners.

(Launched from trebuchets) these thunderclap bombs came dropping down from the air, and upon meeting the water exploded with a noise like thunder, the sulphur bursting into flames.

The carton case rebounded and broke, scattering the lime to form a smoky fog, which blinded the eyes of men and horses so that they could see nothing.

[43] The Song fleet used trebuchets to bombard the Jin ships with incendiary bombs (pili huoqiu 霹雳火球 or huopao 霹雳火砲; "thunderclap fire balls") that contained a mixture of gunpowder, lime, scraps of iron, and a poison that was likely arsenic.

[39] Reports that the bomb produced a loud sound suggests that the nitrate content of the gunpowder mixture was high enough to create an explosion.

The technological advances of the Song navy ensured its access to the East China Sea, where they competed with the military forces of Jin and Mongol rivals.

Caishi was held in the same esteem as the Battle of Fei River in 383, when the Eastern Jin defeated the northern invaders of the Former Qin.

There was a widespread disapproval of his reign in the empire, and Wanyan Liang's policies had alienated Jurchens, Khitans, and Han alike.

He had been enthroned weeks before the assassination, in a military coup that installed him as emperor while Wanyan Liang was absent from the court.

[36] The reasons for his abdication are complicated,[50] but Gaozong's handling of the war with Wanyan Liang may have had a part in his decision to resign.

[32] Military clashes continued in Huainan and Sichuan, but Jin incursions after Caishi had no intent of reaching the Yangzi.