 Early rudimentary bombs like the huopao fire bomb ( 火礮 ) and the huopao ( <unk> ) bombs propelled by <unk> were also in use as incendiary weapons . The defending Song army used huopao ( 火礮 ) during the first Jin siege of Kaifeng in 1126 . On the opposing side , the Jin launched incendiary bombs from siege towers down onto the city below . In 1127 , huopao ( 火礮 ) were employed by the Song troops defending De 'an and by the Jin soldiers besieging the city . The government official Lin <unk> ( <unk> ) proposed to make incendiary bombs and arrows mandatory for all warships in the Song navy . At the battle of Caishi in 1161 , Song ships fired <unk> <unk> ( <unk> ) , also called <unk> huopao bombs ( <unk> ) , from <unk> against the ships of the Jin fleet commanded by Wanyan Liang . The gunpowder mixture of the bomb contained powdered lime , which produced <unk> smoke once the casing of the bomb shattered . The Song also deployed incendiary weapons at the battle of <unk> during the same year . 
