 Gunpowder was also applied to arrows in 1206 by a Song army stationed in Xiangyang . The arrows were most likely an incendiary weapon , but its function may also have resembled that of an early rocket . At the Jin siege of Qizhou ( 蘄州 ) in 1221 , the Jurchens fought the Song with gunpowder bombs and arrows . The Jin tiehuopao ( 鐵火砲 , " iron huopao " ) , which had cast iron casings , are the first known bombs that could explode . The bomb needed to be capable of detonating in order to penetrate the iron casing . The Song army had a large supply of incendiary bombs , but there are no reports of them having a weapon similar to the Jin 's detonating bombs . A participant in the siege recounted in the Xinsi Qi Qi Lu ( 辛巳泣蘄錄 ) that the Song army at Qizhou had an arsenal of 3000 huopao ( 火礮 ) , 7000 incendiary gunpowder arrows for crossbows and 10000 for bows , as well as 20000 pidapao ( 皮大礮 ) , probably leather bags filled with gunpowder . 
 Gunpowder was also applied to arrows in 1206 by a Song army stationed in Xiangyang . The arrows <a href='uninflect' title='1'><mark>were</mark></a> most likely an incendiary weapon , but its function may also <a href='been_done' title='2'><mark>have</mark></a> resembled that of an early rocket . At the Jin siege of Qizhou ( 蘄州 ) in 1221 , the Jurchens fought the Song with gunpowder bombs and arrows . The Jin tiehuopao ( 鐵火砲 , " iron huopao " ) , which <a href='been_done' title='3'><mark>had</mark></a> cast iron casings , <a href='drop_aux' title='4'><mark>are</mark></a>the first known bombs <a href='null_relcl' title='5'><mark>that</mark></a>could explode . The bomb needed to be capable of detonating in order to penetrate the iron casing . The Song army had a large supply of incendiary bombs , but <a href='dey_it' title='6'><mark>there</mark></a> are no reports of them having a weapon similar to the Jin <a href='null_genetive' title='7'><mark>'s</mark></a>detonating bombs . A participant in the siege recounted in the Xinsi Qi Qi Lu ( 辛巳泣蘄錄 ) that the Song army at Qizhou had an arsenal of 3000 huopao ( 火礮 ) , 7000 incendiary gunpowder arrows for crossbows and 10000 for bows , as well as 20000 pidapao ( 皮大礮 ) , probably leather bags filled with gunpowder . 
Gunpowder was also applied to arrows in 1206 by a Song army stationed in Xiangyang . The arrows was most likely an incendiary weapon , but its function may also done resembled that of an early rocket . At da Jin siege of Qizhou ( 蘄州 ) in 1221 , tdaJurchens fought the Song w gunpowder bombs and arrows . The Jin tiehuopao ( 鐵火砲 , " iron huopao " ) , which done cast iron casings , the first known bombs could explode . Thdaomb needed to b capable of detonating in order to penetrate thedaon casing . The dag army had a large supply of incendiary bombs , but it ain't no reports of them having a weapon similar to the Jin  detonating bombs . A participant in the sdae recounted in the Xinsi Qi Qi Lu ( 辛巳泣蘄錄 ) that the Song army at Qizhou had an arsenal of 3000 huopao ( 火礮 ) , 7000 incendiary gunpowder arrows for crossbows and 10000 for bows , as well as 20000 pidapao ( 皮大礮 ) , prob leather bags filled with gunpowder .