The Battle of Lang-Shang Jiang was a naval (river) battle which occurred in 919 (not 932 as is often cited) during the Five Dynasties and Ten Kingdoms period in China between the states of Wuyue and Wu.
The two forces would appear equal; roughly 500 dragon ships on each side (see dragon boat for more). The Wuyue were commanded by Wen-Mu-King and the Wu by Chien Yuan Kuan. The Wuyue however had an ace, a double pump flamethrower. This flamethrower may have used gunpowder to ignite the petrol (Greek fire.) Wen-Mu-King apparently had the flamethrower (or flamethrowers) decorated with silver so that if the enemy captured it they'd take the silver and leave the petrol and apparatus.
The Wuyue managed to destroy with their flamethrower 400 enemy ships then captured 7000 prisoners.
Personal analysis of Battle
The source describes both sides as having "dragon like ships". These could simply be normal war boats with dragon heads carved on. However, in Chinese culture, there are canoes with dragon heads which are used for various sporting events, in honor of an ancient Chinese philosopher. If they were using these types of boat, then it could be that normal military equipment (i.e. warships) was in short supply, and considering the chaos of this time, that could be possible. This could be the reason why they started inventing the flamethrowers, since oil at this stage was quite abundant in the rocks around some parts of China. We know from the Wujing Zongyao from 1044 (although the most recent edition is from the 1560s) that at that stage fire drug (proto-gunpowder) was being used to ignite oil from flamethrowers. It could therefore be that in the chaos, Wen-Mu-King may have started using what was then a type of medicine (or at the most, entertainment) as a slow match for his flamethrowers.
The flamethrower would go on to be an effective but dangerous weapon for the Chinese. Gunpowder (probably already used in incendiary arrows and primitive grenades (study Early thermal weapons) would go on to be used in more effective and terrorizing ways in China and the world.
Due to the obscurity of this battle and the associated war, there is a lot I don't know, apart from what I have read and guessed. I don't know why the Wu and Wuyue were fighting, but I do know that this was a time of political fragmentation generated by generals having too much power, so it could have been anything, but I imagine it would have been over land, canals etc. I also don't know about the significance of the battle, but I imagine that with such a total victory for the Wu that it was quite significant.
- Joseph Needham. Science and Civilization in China V7:5 the Gunpowder Epic