Battle of Sacheon ( 1598 ) The 1598 battle of Sacheon ( 泗川 ) was a siege by Korean and Chinese forces against the Japanese fortification of Sacheon on September 28 – 29 , 1598 , during Toyotomi Hideyoshi ' s invasions of Korea . The Japanese were able to withstand the siege , and due to a fortuitous explosion in the Chinese artillery unit ' s powder magazine , attacked and drove off the Chinese and Korean army . There are conflicting accounts of how many men participated and how many were killed , but all accounts agree that the Japanese garrison was heavily outnumbered and emerged victorious . Background . Sacheon is a natural harbor located on the southern coast of Korea , in what was then called Jeolla province . Shimazu Yoshihiro and his son Tadatsune came to Sacheon in 1597 after aiding in the Japanese capture of the fortress of Namwōn . There , they built a new Japanese - style castle directly on top of the old Silla fort , and shortly afterwards another , larger castle right at the port , about six kilometers to the south . By 1598 , this new castle contained an inner wall around the keep , surrounded by a natural moat which filled with sea water during high tide only , allowing ships to enter the moat . The outer wall encompassed a much larger area with additional guntowers and several fortified gates . As with many battles during the Imjin war , the three accounts ( Chinese / Korean / Japanese ) vary wildly in the deciding factor for the outcome of the battle , and more importantly in headcount , regarding both men deployed and lost . Some Japanese sources claim that the Ming army had up to 200 , 000 soldiers , which was nearly triple the number of the total men the Ming sources said they deployed in the entire Korean campaign . The Ming sources said they had a combined strength of 30 , 000 at the siege , yet the Japanese source most widely cited claimed 37 , 000 heads were taken . Korean sources said the allies lost about 7 to 8 thousand men . Siege . Koreans and their Ming Chinese allies began pushing south in 1598 , reclaiming territory lost to the Japanese in the battles of the preceding years . By September , an army of 34 , 000 Chinese warriors under the command of Dong Yiyuan 董一元 , along with 2000 Korean warriors , was ready to lay siege to the newer , larger Sacheon castle . Murakami Tadazane , commander of the smaller garrison , brought his 300 men to the larger castle , joining up with Shimazu Yoshihiro ' s force of 8 , 000 , before the Chinese / Korean force began their assault on October 1 . The allied forces began their assault at midnight on September 28 . The old castle fell quickly at about 3 : 00 a . m . on the next day , and the Japanese split their force in three , retreated and sallied forth from the new castle ' s three gates . A big fire suddenly appeared at the rear of the besiegers and sent them into chaos . The Japanese stormed forth and defeated them . According to the chronicle of the Shimazu clan , 37 , 000 heads were taken ; and still numerous dead bodies were left on the battle field . A hole was dug , twenty " ken " across ( about 36 meters ) , to bury the bodies . Chinese contemporary sources such as Dong Yiyuan ' s biography in the official history of Ming ( 忽營中砲裂 ， 煙焰漲天 。 賊乘勢衝擊 ， 固城援賊亦至 ) and ( 諸葛元聲 《 兩朝平壤錄 ) ( The two trips to Pyongyang by Zhuge Yuansheng ) wrote that the cause of the defeat was a serious artillery explosion that triggered a massive chain explosion of the entire Ming army gunpowder cache , which sent the army into complete disarray , and the Japanese took advantage of the moment and sallied forth . The artillery division , some 3000 men from Zhejiang province , suffered the highest casualties , only about 50 men reported back to the army after the dust had settled .