The Walls Came Tumbling Down: Siege Guns

^{Soldiers in the early 19th century operate heavy siege mortars.}

The Chinese first made guns of paper and bamboo, but neither substance could contain much pressure. That meant the gun could neither fire a very heavy missile or use a very heavy powder charge without bursting. And that meant that these paper and bamboo guns never became important weapons.

They were probably most useful for tossing light incendiary projectiles at inflammable targets. Even after they had metal cannons, the Japanese used them to shoot paper packages of oil‑soaked gunpowder at the wooden superstruc‑tures of samurai castles to burn them down.

Europeans, on the other hand, made their cannons of metal from the beginning. By the 13th century, when gunpowder became known in the West, Europe led the world in the technology of bronze casting. European bronze founders had learned the secrets of making large castings by decades of casting bells for Christian churches. Bronze was expensive, so some European gunmakers used iron instead. There were no European blast furnaces at that time, so the first iron cannons could not be cast. Instead, the gunmaker welded a large number of wrought iron rods together around a mandrel, then bound them together with iron hoops, heated red‑hot and forced over the cylinder of welded rods. As the hoops cooled, they shrank and bound the rods tightly. The whole process resembled the manufacture of a barrel, which is why we now call the tube of a gun that the projectile passes through a barrel.

The early iron guns, having been welded around a cylindrical mandrel, were straight tubes. The bronze guns, however, were shaped on the outside like a flower vase, but the interior was cylindrical. The founders apparently wanted to put more metal around the part of the gun where the powder exploded. These earliest cannons fired balls of stone, lead, or brass and heavy, arrow‑shaped projectiles. The earliest picture of a cannon we have is on a manuscript prepared by Walter de Milemete for his pupil, the future King Edward III of England. It shows one of these vase‑shaped cannons being ignited by a man in armor. Emerging from the mouth of the cannon is a large arrow.

When he grew up, Edward III took three primitive cannons with him to France and used them at the battlefield of Crecy. These novel weapons may have helped panic the mercenary Genoese crossbowmen in the French army.

On the battlefield, the most potent feature of these early cannons was the flash and noise they made. They could scare horses and troops unfamiliar with gunpowder weapons. But for actual destruction, one of these small, primitive cannons didn’t compare with a good bow or crossbow.

That was not true when they were used for sieges. For sieges, medieval kings ordered enormous guns that shot stone balls weighing hundreds of pounds.

Some of these guns were so heavy they were cast in two pieces to make them easier to move. The halves were screwed together after they were dragged into position. When Mohammed the Conqueror, sultan of Turkey, laid siege to Constantinople, he told his gun founder, a renegade Hungarian named Urban, that he wanted the biggest guns ever seen. Urban told him it would be easier to cast the guns right in front of Constantinople than to move them from a foundry.

So they were cast just out of range of the defenders’ weapons.

Once they were in position, these huge cannons, called bombards, were completely immobile. They were enclosed in wooden frames that had been constructed around them. Immobility didn’t matter. The task of the gunners to was to shoot one huge cannonball after another at the same spot on a wall. It did not take long for the wall to collapse. That was an effect that could seldom be achieved with mechanical artillery.

The introduction of siege guns had a profound effect on the techniques of warfare, and an even more profound effect on European society in general.

Designers of fortresses made the walls lower and thicker. They learned that while stone walls would shatter when hit by cannon balls, earth walls would just soak up the missiles. Earth walls, though, could be eroded by weather. Eventually, military engineers built earthen walls faced by stone and reinforced internally so that, if a breach was made in the stone, the dirt wouldn’t pour through the break, making a convenient ramp for attackers. The engineers surrounded their forts with deep, wide ditches. Outside these ditches were sloping embank‑ments that hid all but the tops of the walls. This sort of embankment, called a glacis, was kept free of any vegetation but grass, so attacking infantry would have no cover. Just behind the top of the glacis, was a path called a covered way from which infantry could fire on attackers making their way up the glacis.

There were wide spots on the covered way where the defenders of a fort could assemble for counterattacks. At the corners of the forts, the engineers built arrowhead‑shaped projections called bastions, where cannons could be placed to subject attackers to crossfire while the guns on the wall fired on them directly. On the flanks of the bastions, protected from fire from the front, were other cannons that could fire down the length of the ditch. In front of the fort proper, but within the ditch, were detached forts connected to the main fortress with draw bridges or tunnels. This type of cannon‑fort took years or even centuries to develop. Most of the early development took place in Italy, where such “renaissance men” as Michelangelo added innovations that made European fortresses by far the strongest in the world.

These modern forts were much larger than the old‑fashioned castles, and they were far more expensive. The forts and the cannons needed to defend them were so expensive that only kings, free cities, and very great lords could afford them. Cannons played a big part in ending the Middle Ages – not because they could knock down any fortification, but because they made practical fortification too expensive for the many minor nobles who had previously cut Europe up into thousands of tiny, almost autonomous, fiefdoms.