Medieval cannons, gunpowder, and the lunatics who used them

I don’t know about you, but when I think of medieval warfare, I imagine it being fought with swords, bows, spears, and the occasional siege engine. I don’t think of cannons and gunpowder. I had assumed explosives only turned up at the very end of the Middle Ages. I was wrong.

So I began investigating the matter. It wasn’t news to me that gunpowder was invented in China in the first millennia AD. What was slightly startling was that Chinese alchemists may have stumbled over the sulphur, charcoal, and saltpetre mix that is gunpowder while looking for an elixir of eternal life. I trust no one ironically lost their lives in the discovery.

(The image to the right is from the 10th century. It shows demons threatening Sakyamuni with a fire lance and grenade!)

We don’t know for sure how gunpowder got from China to Europe (maybe via the Mongols, maybe along the Silk Road), but Roger Bacon was writing about an explosive powder by 1267, and the oldest written recipes for gunpowder in Europe appear between 1280 and 1300 in Marcus Graecus’s Liber Ignium, or Book of Fires. From that point on, you’d think that pugnacious Europeans would grasp the potential of making things go bang with indecent haste, but no. Gunpowder doesn’t seem to have much been used for hostile purposes until the 1320s, and even then, it didn’t revolutionise warfare immediately. It was more of a slow burn.

(Image of a very early European cannon, from Walter de Milemete's De Nobilitatibus Sapientii Et Prudentiis Regum, 1326.)

So what was holding gunpowder back in the 1300s? Why didn’t military commanders grasp its explosive potential for destruction more quickly? Here are a handful of the more important reasons:

o early cannons were very inaccurate;

o they were very slow to load and refire (maybe 5 to 6 shots per day);

o gunpowder was very expensive in the 1300s;

o cannons were heavy and hard to manoeuvre.

Then there was the danger involved in handling cannons. It wasn’t just those being fired at who were in danger of injury or death – being a military engineer was a hazardous occupation. The intense pressure gunpowder exerted on the interior of the cast metal sometimes caused the cannon itself to shatter. If the cannon were cast of iron, deadly shards would fly all around, decimating bystanders. One famous casualty of such friendly fire was King James II of Scotland at the siege of Roxburgh, in 1460. The immobility of a cannon, combined with its loudly advertised presence, also made it and its operators a prime target for enemy attack. Kill the gunmen, and you stop the nasty cannonballs.

Not only was firing cannons a job reserved for madmen, but it required considerable technical know-how. Cannons fired at an incredibly slow rate because they required careful and laborious loading. As Clifford Rogers tells us:

working from the mouth of the weapon, the gunner had to ladle and pack in enough powder to fill 3/5 of the chamber, and then plug the opening tightly with a wooden tampon that filled another fifth of the space, leaving an equal volume of empty air between the powder and the wood. The ball was then loaded in, wedged in place with triangular pieces of soft wood, and covered with some mixture of mud, loam and hay, which then had to be allowed to dry. All of this served to keep the ball in place as a plug for the powder chamber until the pressure of the gas generated by the burning powder built to a high level

Then BANG! But only if the gunpowder you put in the cannon was prepared properly and hasn’t absorbed so much water since that it is largely useless. (Early gunpowder was hygroscopic: it absorbed water, and wet things don’t tend to burn well.) Add to that, the correct proportions of sulphur, saltpetre, and charcoal were hotly debated, and saltpetre itself (potassium nitrate) was very expensive and hard to acquire.

Why all this investigation into the fickle and deadly beast that was medieval gunpowder? I wanted to get a secondary character right. In The Assassin and Her Knight, my heroine joins a small mercenary company in 1360s France. Its least attractive and most lovable member is John “The Wreck”, a man besotted with gunpowder. He’s not particularly murderous, just a man with an explosive obsession—a very useful insanity in the context of fourteenth-century warfare.

Further Reading:

Cressy, D., Saltpeter: The Mother of Gunpowder, Oxford University Press, 2013.

Hamer, M., “Blast from the Past”, New Scientist, vol. 188, iss. 2524, 2005, pp. 33-35.

Rogers, C.J., “Gunpowder Artillery in Europe, 1326-1500: Innovation and Impact”, in D. Curzon, et al (ed’s), Technology, Violence, and War: Essays in Honor of Dr. John F. Guilmartin, Brill, 2019, pp. 39-71.