text: battle of caishi the battle of caishi ( battle of ts 'ai - shih ; chinese : ) was a major naval engagement of the jin – song wars of china that took place on november 26 – 27 , 1161 . soldiers under the command of wanyan liang ( the prince of hailing ) , the jurchen emperor of the jin dynasty , tried to cross the yangtze river to attack song china . yu yunwen , a civil official , commanded the defending song army . 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 . starting in 1125 the jin had conquered all song territories north of the huai river . in 1142 , a peace treaty settled the border between the two states , putting the jin in control of northern china and the song in control of the south . wanyan liang was enthroned in 1150 , and was intent on uniting northern and southern china under a single emperor . in 1158 , he asserted that the song had violated the 1142 treaty , a pretext for declaring war on the song . he began preparations for the war in the following year . he instituted a draft in which all able - bodied men were required to enlist . the draft was unpopular , precipitating revolts that were later suppressed . the jin army left the capital of kaifeng on october 15 , 1161 , and pushed through from the huai to the yangtze river without much resistance from the song . the song were fortified along the yangtze front . wanyan liang planned to cross the river at caishi , south of modern - day nanjing . he embarked from the shore of the yangtze on november 26 , and clashed with song forces led by yu yunwen in a naval engagement . wanyan liang lost the battle and retreated to yangzhou . wanyan liang was assassinated in a military camp by his own men shortly after the caishi battle . a military coup had taken place in the jin court while wanyan liang was absent , emperor shizong as the new emperor . a peace treaty signed in 1165 ended the conflict between song and jin . song sources likely inflated the number of jin soldiers and casualties 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 boosted the morale of the song infantry and halted the southern advance of the jin army . background the song ( 960 – 1276 ) was a chinese dynasty . to their north were the jurchens , a confederation of semi - agrarian tribes from manchuria in northeast asia . while the song and jurchen had once been military allies , the jurchen tribes , unified under the rule of wanyan aguda , plotted a revolt in 1114 to end their vassalage under the khitan - led liao dynasty . aguda established the jin dynasty in 1115 and adopted the title of emperor . the jin negotiated a joint attack with the song against the khitans . they planned the attack for 1121 and then rescheduled to 1122 . in 1122 , the jurchens captured the liao supreme and western capitals . the song tried yet failed to capture the liao southern capital of yan ( modern beijing ) , which fell later that year to the jin . the military weakness of the song gave the jin more diplomatic leverage over the song . negotiations between the song and jin produced a treaty in 1123 , but bilateral relations deteriorated because of territorial disputes over the sixteen prefectures . in 1125 , the jurchens invaded the song . by 1127 , jin had conquered most of northern china and besieged the song capital of kaifeng twice . in the second siege of kaifeng , emperor qinzong of the song was captured . the jurchens took him and the song royal family to manchuria as hostages . members of the song court who had evaded capture fled south , where they established a temporary capital , first in the song southern capital ( modern shangqiu ) , and then in hangzhou in 1129 . the move of the song capital south to hangzhou signals the transition from the northern song era to the southern song . qinzong 's younger brother , prince zhao gou , was enthroned as qinzong 's successor in the southern capital in 1127 ; he is known posthumously as emperor gaozong . the jurchen general wuzhu crossed the yangtze river in 1130 and tried to capture gaozong , but the emperor escaped . wuzhu retreated north across the yangtze , where he fought off a stronger song fleet commanded by han shizhong . the jin persisted with their advance into the remaining song territories south of the yangtze . they faced an insurgency of song loyalists in the north , the deaths of some important leaders , and military offensives by song generals like yue fei . the jurchens created the puppet government of da qi to serve as a buffer state between song and jin , but qi failed to defeat the song . the jin abolished qi in 1137 . as the jin gave up on conquering the southern song , diplomatic talks for a peace treaty resumed . signed in 1142 , the treaty of shaoxing established the boundary between the two states along the huai river , which runs north of the yangtze . the treaty forbade the song from purchasing horses from the jin , but smuggling continued in the border markets . the relations between the two states were mostly peaceful from 1142 to 1161 , the year wanyan liang went to war . preparation for war wanyan liang was crowned jin emperor in 1150 after killing his cousin and predecessor , emperor xizong , in a palace coup . wanyan liang considered himself more of a chinese authoritarian ruler than a jurchen leader who ruled through a tribal council . the history of jin contends that wanyan liang told his officials that the three desires of his life were conquest , absolute power , and women . his ultimate ambition was to rule over all of china , not just the north . in his childhood , wanyan liang adopted song practices like drinking tea by learning from song emissaries , and once he had become emperor , he pursued a policy of the state . his affinity for the culture of the song earned him the jurchen nickname of " aping the chinese " . he moved the supreme capital of the jin from huining in manchuria to beijing and promoted kaifeng to his southern capital in 1157 . he also moved government institutions south , tore down palaces of jurchen chieftains in manchuria , and constructed new palaces in beijing and kaifeng . he made plans to move the jin capital further south to the center of china . wanyan liang 's construction projects drained the jin treasury . plans for a war against the southern song began in 1158 . that year , wanyan liang claimed that the song had broken the 1142 treaty that banned them from acquiring horses . in 1159 , he began building up his army in preparation for an invasion . he acquired weapons , which he stored in beijing , as well as horses allegedly numbering 560 , 000 . wanyan liang understood that an invasion of the song would require a lot of men . he ensured that han chinese soldiers were drafted into the war effort alongside jurchen soldiers . the recruitment drive lasted until 1161 . naval confrontations were likely because the jin planned on traveling by river . ships were seized for the war and 30 , 000 of the recruits were assigned to the jin fleet . wanyan liang authorized the building of ships for the war in march 1159 , under the auspices of the ministry of war . construction began in the tong ( ) prefecture near beijing . wanyan liang appointed himself head of the army and took personal command of the jurchen forces . the draft was unpopular . several revolts erupted against it , many of them in the jin provinces neighboring the song . but wanyan liang allowed no dissent . he had his stepmother executed after hearing that she was critical of the war effort . in order to eliminate any challenge to his legitimacy as emperor of a united china , wanyan liang ordered the execution of all male members of the song and liao royal families residing in jin territory . 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 manchuria . they refused to be drafted into the army , maintaining that conscription would leave the homeland of the khitans unprotected from rival tribes on the steppes . wanyan liang rebuffed their demands . the khitan rebels killed several jurchen officials . the rebellion was fragmented , and there were separate plans either to spread the revolt further by operating from shangjing , the former liao capital , or to move the khitan people from manchuria to central asia , where the kara - khitan khanate had formed after the demise of liao . wanyan liang was forced to divert resources and men away from the war effort to suppress the rebellion . diplomatic exchanges between the song and jin did not stop during the period preceding the war . the history of song claims that the song realized that the jin were planning for an invasion when they noticed the discourtesy of one of the jin diplomats . some song officials foresaw the impending war , but emperor gaozong hoped to maintain peaceful relations with the song 's northern neighbor . his reluctance to antagonize the jin delayed the fortification of the song border defenses . the song quickly built just three military garrisons in 1161 . wanyan liang departed from kaifeng on october 15 , 1161 . the offensive comprised four armies , and wanyan liang personally led the army that entered anhui . the jin passed the huai river boundary on october 28 , advancing into song territory . the song resistance was minimal because they had fortified the southern shore of the yangtze river and not the huai . naval battle wanyan liang 's army built its encampment near yangzhou on the northern side of the yangtze river . the jin advance had been slowed by song victories in the west , where the song captured several prefectures from the jin . wanyan liang commanded his forces to cross the yangtze at caishi , south of modern nanjing . a naval battle between jin and song took place on november 26 and 27 , 1161 . the song troops were led by yu yunwen – a scholar - official – and his lieutenants dai gao , jian kang , shi , and others . yu , who was a drafting official of the secretariat ( ) , was at caishi to distribute awards to song soldiers who had been selected for their outstanding service ; it was by chance that his visit coincided with wanyan liang 's campaign . when he first arrived , the song forces at caishi were scattered and lacked a central leader . yu took command and built a cohesive army . the jin performed a ritual sacrifice of horses a day before the battle . on november 26 , jin troops embarked from the shore of the yangtze and engaged the song fleet . some of the ships they boarded were shoddily built . the jin had lost several ships in liangshan , where they were bogged down by the shallow depths of liangshan lake as they were being transported to the grand canal . wanyan liang had urgently requested the construction of more ships in 1161 to compensate for those still stuck in liangshan . 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 . the song military response was likely stronger than wanyan liang had anticipated . the paddle - wheel ships of the song navy could move more rapidly and outmaneuver the slower jin ships . the song kept their fleet hidden behind the island of shan . the ships were to depart the island once a scout on horseback announced the approach of the jin ships by signalling a concealed flag atop the island 's peak . once the flag became visible , the song fleet commenced their attack from both sides of the island . song soldiers operated traction trebuchets that launched incendiary " thunderclap bombs " and other soft - cased explosives containing lime and sulphur , which created a noxious explosion when the casing broke . the jin soldiers who managed to cross the river and reach the shore were assaulted by song troops waiting on the other side . the song won a decisive victory . wanyan liang was defeated again in a second engagement the next day . after burning his remaining ships , he retreated to yangzhou , where he was assassinated before he could finish preparations for another crossing . estimates for the number of soldiers and casualties at the battle vary widely . a song source reports that there were 18 , 000 song soldiers stationed in caishi , a number that historian herbert franke considers plausible . however , song estimates for the number of jin troops are likely inflated . one document claims that 400 , 000 jin soldiers were present at the battle . this number is doubtful , bearing in mind that the song had only 120 , 000 soldiers fighting on the entire front . song historians may have confused the total number of jin personnel deployed on the front with the number of jin combatants at caishi . the inflated figure could have referred to the number of soldiers that the jin army had before crossing the huai river toward the yangtze . the desertions and casualties from suppressing revolts while advancing southward would have shrunk that number by the time the jin reached the yangtze . the history of jin , a document written from the perspective of the jin , reports jin casualties between one meng 'an ( a jurchen unit of a thousand soldiers ) and a hundred men , and two meng 'an and two hundred men . the history of song reports jin casualties numbering four thousand soldiers and two commanders of ( ten thousand men ) rank . 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 . a more conservative song source estimates that the jin only had 500 soldiers and 20 ships at caishi . it is not certain which of these figures is more accurate ; franke believes that the safest conclusion that can be drawn is that the number of jin casualties was not greater than four thousand . military and naval technology an account of the song 's technological capabilities is given in the hai qiu fu ( " ode on the sea - eel paddle wheel warships " ) : the men inside them paddled fast on the treadmills , and the ships glided forwards as though they were flying , yet no one was visible on board . the enemy thought that they were made of paper . then all of a sudden a thunderclap bomb was let off . it was made with paper ( carton ) and filled with lime and sulphur . ( 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 . our ships then went forward to attack theirs , and their men and horses were all drowned , so that they were utterly defeated . there were up to 340 ships in the song fleet during the battle of caishi in 1161 . the song fleet used trebuchets to bombard the jin ships with incendiary bombs ( pili huoqiu or huopao ; " thunderclap fire balls " ) that contained a mixture of gunpowder , lime , scraps of iron , and a poison that was likely arsenic . 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 powdered lime in the bombs at caishi generated a cloud of blinding smoke similar to tear gas . the huoqiu released the smoke once the casing of the bomb shattered . activated the bombs after launching . the jin conscripted thousands of blacksmiths to build the armor and weaponry of the fleet , and workers to dig out the canal necessary for transporting the ships from tong to the grand canal through the northern port of ( ) , modern tianjin . the jin armored their light ships with thick rhinoceros hides . the ships had two stories ; on the lower deck were the oarsmen responsible for rowing the ship , while soldiers on the upper deck could fire missile weapons . three different variations of the warships were constructed . several of the ships became bogged down in liangshan , and the ships built to replace them were of an inferior quality . the jin fleet were unable to defeat the larger and faster warships of the song . the battle is significant in the technological history of the song navy . 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 . although huopao launched by the ship - mounted trebuchets had been invented decades earlier , the bombs did not become mandatory on song warships until 1129 . paddle - wheel ships operated with treadmills were constructed continuously in various sizes between 1132 and 1183 . the engineer gao xuan devised a ship outfitted with up to eleven paddle wheels on each side , and qin , another engineer , designed the iron plating for armoring the ships in 1203 . all these advances supported a rapid increase in the size of the force ; according to the 20th - century historian joseph needham , " from a total of 11 squadrons and 3 , 000 men [ the song navy ] rose in one century to 20 squadrons totalling 52 , 000 men " . aftermath traditional chinese historiography celebrated the battle of caishi as an important victory for china . 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 . however , its portrayal as a victory against overwhelming odds , in which 18 , 000 song soldiers overcame an army of nearly half a million men , is likely an exaggeration . modern historians believe that the number of jin soldiers was far lower . the song possessed multiple advantages , and the battle was more evenly matched than contemporaneous historians suggest . the song had larger ships and ample time to prepare while the jin army gathered supplies and ships for the crossing . it was also impossible for the jin to use cavalry , the most important asset of the jurchen military , during a naval engagement . a modern analysis of the background of the conflict and the battlefield has also shown that it was a smaller engagement than traditionally believed . its effects were more psychological than material . the battle was not solely responsible for dooming wanyan liang 's military campaign ; his own failings also led to his downfall . wanyan liang 's generals detested him , and his relationship with his men had deteriorated over the course of the war . his authoritarianism made him equally unpopular among his own people . there was a widespread disapproval of his reign in the empire , and wanyan liang 's policies had alienated the jurchens , the khitans , and the han chinese . disaffected officers conspired to kill him , and he was assassinated on december 15 , 1161 . emperor shizong succeeded wanyan liang as ruler of the jin . 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 . shizong eventually rescinded many of wanyan liang 's sinification policies . the victory boosted the morale of the song soldiers and increased dissatisfaction among the jin army . news of the victory improved confidence in the government and bolstered the stability of the song . the jurchens gave up their ambitions of conquering the southern song and reunifying china . the jin army withdrew in 1162 , and diplomatic relations between the two states resumed . emperor gaozong retired nine months after the conclusion of the battle . the reasons for his abdication are complicated , but gaozong 's handling of the war with wanyan liang may have had a part in his decision to resign . he had ignored the warnings of a jin attack and his hopes for conciliation held back plans for strengthening the song defenses . military clashes continued in huainan and sichuan , but jin incursions after caishi had no intent of reaching the yangtze . the jin had discovered that southern china 's many lakes and river impeded their cavalry . they signed a peace treaty with the song in 1165 , ending hostilities . the huai river border remained the same and the song continued to pay annual indemnities to the jin , but the song no longer recognized their state as a jin vassal .