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Early in 1452, a Hungarian cannon founder by the name of Orban arrived in Constantinople, seeking his fortune at the imperial court. One of a growing band of technical mercenaries who plied their trade across the Balkans, he offered Emperor Constantine XI one of the most highly prized skills of the age: the ability to cast large bronze guns.

For Constantine and the Christian empire of Byzantium that he ruled, these were dark days. For 150 years the Byzantine frontier had been crumbling before the advance of the Ottoman Turks. By the time Constantine assumed the throne in 1449, his impoverished kingdom had shrunk to little more than the footprint of the city, surrounded on all sides by Ottoman land. The new sultan, Mehmed II—young, ambitious and hungry for conquest—was making ominous military preparations in his European capital, Edirne, 140 miles to the west. It was clear he was intent on capturing the prize that had eluded previous Ottoman rulers: Constantinople.

Constantine was extremely interested in Orban’s offer and authorized a small stipend to detain him in the city. But Constantine had few funds available for the construction of new weapons. Bronze cannons were ruinously expensive, well beyond the means of the cash-strapped emperor. Orban’s tiny allowance was not even paid regularly, and as the year wore on, the master craftsman became destitute. So later that same year he decided to try his luck elsewhere. He made his way to Edirne to seek an audience with the young sultan.

At the time, Mehmed was racked by indecision over Constantinople. The city was the ultimate prize; it would provide a fitting capital for the Ottoman Empire, and its capture was the subject of ancient Muslim prophecies, attributed to Muhammad himself, that predicted great honor for its eventual conqueror. However, Constantinople had repulsed repeated Muslim assaults from the 7th century onward. Its triangular site made it all but impregnable: Two sides were surrounded by sea, and the third landward side was commanded by the great Walls of Theodosius, a defensive line four miles long, the greatest bastion in the medieval world. In a thousand years the city had been besieged some 23 times, but no army had found a way to crack open those land walls.

Accordingly, Orban’s arrival at Edirne must have seemed providential. The sultan welcomed the master founder and questioned him closely. Mehmed asked if he could cast a cannon to project a stone ball large enough to smash the walls at Constantinople. Orban’s reply was emphatic: “I can cast a cannon of bronze with the capacity of the stone you want. I have examined the walls of the city in great detail. I can shatter to dust not only these walls with the stones from my gun, but the very walls of Babylon itself.” Mehmed ordered him to make the gun.

During the autumn of 1452, Orban set to work at Edirne, casting one of the largest cannons ever built, while Mehmed stockpiled substantial quantities of materials for guns and gunpowder: copper and tin, saltpeter, sulfur and charcoal. Workers excavated an enormous casting pit and melted scrap bronze in the brick-lined furnaces, superheating it with bellows and pouring it into the mold.

What finally emerged from Orban’s foundry once the molds had been knocked off was “a horrifying and extraordinary monster.” It was 27 feet long. The barrel, walled with 8 inches of solid bronze to absorb the force of the blast, had a diameter of 30 inches, enough for a man to enter on his hands and knees and designed to accommodate a stone shot weighing something over half a ton. In January 1453, Mehmed ordered a test firing of the gun outside his royal palace. The mighty bombard was hauled into position near the gate and primed with powder. Laborers lugged a giant stone ball to the mouth of the barrel and rolled it back to sit snugly against the gunpowder chamber. A lighted taper was put to the touchhole. With a shattering roar and a cloud of smoke, the mighty projectile hurled across the countryside for a mile before burying itself six feet into the soft earth.

Mehmed now addressed the challenge of transporting the gun the 140 miles to Constantinople. Two hundred men and 60 oxen were detailed for the task. The immense barrel was loaded onto several wagons chained together and yoked to the ox teams. The great gun rumbled toward the city at a speed of two and a half miles a day, while another team of engineers worked ahead, leveling roads and building wooden bridges over rivers and gullies. Orban’s foundry continued to turn out barrels of different sizes; none was as large as the first supergun, though some measured more than 14 feet.

It took six weeks for the guns to lurch and jolt their way to Constantinople. By the time they arrived, in early April, Mehmed’s army—a huge force of 80,000 men—was dug in along the length of the land walls. Sappers had cut down orchards and vineyards outside the Walls of Theodosius to provide a clear field of fire. Others dug a ditch the length of the walls and 250 yards from them, with an earth rampart to shield the guns. Within the city walls, a mere 8,000 men awaited the inevitable assault.

Mehmed grouped the cannons into 14 or 15 batteries along the walls at key vulnerable points. Orban’s supergun, which the Greeks called the Basilica cannon—“the royal gun”—was positioned in front of the sultan’s tent so he could critically appraise its performance. Each large cannon was supported by a cluster of smaller ones in a battery the Ottoman gunners named “the bear with its cubs.” They could fire stone balls ranging from 200 pounds up to a colossal 1,500 pounds, in the case of Orban’s monster gun. Though eyewitnesses spoke of “innumerable machines,” Mehmed probably had about 69 cannons, a huge artillery force by the standards of the day. They were augmented by more traditional technologies for hurling stones, such as the trebuchet. The latter had been effective in the Muslim capture of crusader castles 300 years earlier, but now it looked like a device from another age.

Installing and readying the cannons was a laborious process. Workers had to erect a massive block-and-tackle system to lower the barrels into position on a sloping wooden platform. Shielding the cannons from enemy fire were a wooden palisade and a hinged door that could be opened at the moment of firing.

The logistical support for this operation was immense. Ships transported loads of black stone balls mined and shaped on the north coast of the Black Sea. The cannons also required substantial quantities of saltpeter. Founders who worked with Orban at Edirne doubled as gun crews, positioning, loading and firing the cannons—even repairing them on site.

Preparing the big cannon to fire required time and attention to detail. Crews would load gunpowder, backed by a wooden or sheepskin wad pounded tight into the barrel. Next they manhandled a stone ball to the muzzle and eased it down the barrel. Each ball was designed to be a good fit, though an exact caliber match was often elusive. Crews set their aim by “certain techniques and calculations” about the target—i.e., trial and error—and adjusted the angle of fire by chocking the platform with wooden wedges. Great timber beams weighted down with stones acted as shock absorbers. Crews then poured priming powder into the touchhole.

On April 12, 1453, lighted tapers were put to the touchholes of the sultan’s guns along a four-mile sector of the front line, and the world’s first concerted artillery barrage exploded to life.

If there is any single moment in the history of warfare at which an authentic sense of awe at the exponential power of gunpowder could be palpably felt, it is here in the accounts of those firing these great guns in 1453. The taper ignited the powder:

And when it had caught fire, faster than you can say it, there was first a terrifying roar and a violent shaking of the ground beneath and for a great distance around, and a din such as has never been heard. Then, with a monstrous thundering and an awful explosion and a flame that illuminated everything round about and scorched it, the wooden wad was forced out by the hot blast of dry air and propelled the stone ball powerfully out. Projected with incredible force and power, the stone struck the wall, which it immediately shook and demolished, and it was itself shattered into many fragments, and the pieces were hurled everywhere, dealing death to those standing nearby.

When the huge stone balls struck the walls at an advantageous spot, the effects were devastating. “Sometimes it destroyed a complete portion of wall,” an eyewitness reported, “sometimes half a portion, sometimes a greater or smaller part of a tower, or a turret, or a parapet, and nowhere was the wall strong enough or sturdy enough or thick enough to withstand it, or to hold out totally against such a force or the velocity of the stone ball.” It must have seemed to the defenders that the whole history of siege warfare was unraveling in front of their eyes. The Walls of Theodosius, the product of two millennia of defensive evolution, crumbled wherever it was hit. The defenders were amazed and horrified by what they saw.

Balls from the superguns that cleared the walls traveled up to a mile into the heart of the city, shattering with devastating force against houses or churches, mowing down civilians or burying themselves in orchards and fields within the walls. According to eyewitnesses, the ground was shaken for two miles around, and even the galleys tied up in the harbors felt the explosions through their wooden hulls.

The psychological effects of the artillery bombardment on the defenders were even more severe than its material consequences. The noise and vibration of the massed guns, the clouds of smoke, the shattering impact of stone on stone dismayed seasoned defenders. To the civilian population, it seemed a glimpse of the coming apocalypse. It sounded, according to one Ottoman chronicler, “like the awful resurrection blast.” People ran out of their houses, beating their chests and crossing themselves. Women fainted in the streets. Churches were thronged with people voicing petitions and prayers.

The defenders tried different methods to mitigate the shock of the stone balls. Some poured a mortar of chalk and brick dust down the walls’ outer face as a hardened coating; others padded the walls with suspended bales of wool, leather sheets and even precious tapestries. These measures made little difference. The defenders also tried to knock out the big guns with their own few cannons, but they were short of saltpeter, and the palisades effectively screened the Ottoman cannons. Worse, the walls and towers proved unsuitable as gun platforms—neither wide enough to accommodate the recoil nor strong enough to withstand the vibrations, which “shook the walls, and did more damage to them than to the enemy.” Their largest cannon soon exploded, enraging the harassed defenders so much that they threatened to put the gun master to death for being in the pay of the sultan. Regardless, it was clear that in this new age of warfare, the Walls of Theodosius were inadequate.

Mehmed’s strategy was attritional—and impatient. He decided to breach the walls with artillery fire and launch unpredictable skirmishes to wear down the defenders prior to a final attack. “The assault continued night and day, with no relief from the clashes and explosions, crashing of stones and cannonballs on the walls,” reported a defender, “for the sultan hoped in this way to take the city easily, since we were few against many, by pounding us to death and exhaustion, and so he allowed us no rest from attack.”

Managing the great cannon remained difficult work. Loading and aiming were such laborious operations that the Basilica could only be fired seven times a day. The guns could be unpredictable and deadly to their teams. In the spring rain, they proved hard to keep in position, recoiling with the slam of a charging rhino and frequently slipping from their cradles into the mud. The possibility of being crushed to death was only exceeded by the risk of being blown to pieces by the shrapnel of disintegrating gun barrels. The Basilica quickly became a cause for concern to Orban; casting on this scale was extremely demanding, and the intense heat of the explosions started to exploit hairline fractures in the impure metal. After each shot, crews soaked the barrel in warm oil to prevent cold air from penetrating and enlarging the fissures.

Their stopgap measure failed. The Basilica soon “cracked as it was being fired and split into many pieces, killing and wounding many nearby.” Strengthened with iron hoops and pressed back into service, it soon cracked again, to Mehmed’s intense anger. The supergun simply exceeded the tolerances of contemporary metallurgy.

In the end, it didn’t matter. Though the supergun inflicted great psychological trauma, the slightly smaller yet still formidable bombards would do the real damage.

In the early days of the bombardment, a deputation of Hungarians visited the sultan’s camp. One observed the firing of the great cannons with interest. Watching a shot strike the walls at a certain point, he laughed to himself as the gunners aimed a second shot at the same point. He advised them to aim their second shot “about 30 to 36 feet from the first shot, but at the same height” and to position a third shot between the two “so that the shots form a triangular shape. Then you will see that portion of wall collapse.” Soon the “bear and cubs” were working as coordinated teams. Smaller guns would make the two outer hits, then one of Orban’s great guns would complete the triangle in the now weakened central section, “the shot being carried by such devilish force and irresistible impetus that it caused irreparable damage.”

The bombardment continued unabated for six days. Despite aiming difficulties and a slow rate of fire, gunners managed to launch about 120 shots a day at the city, concentrating their heaviest fire on the central section of wall. Inexorably, the walls began to crumble. Within the week a section of the outer wall had fallen, as had two towers and a turret on the inner wall.

However, after their initial terror at the bombardment, the defenders had regained heart and now worked unceasingly to repair the damage. They devised an effective ad hoc solution to shore up the outer wall, constructing a makeshift replacement of stakes reinforced with any material that came to hand, including stones, timber, brushwood, bushes and large quantities of earth. The defenders placed barrels full of soil at regular intervals to create firing positions that would absorb Ottoman arrows and bullets. At dusk men and women came up from the city to work all night, carrying timber, stones and earth to rebuild smashed defenses. The resulting earthworks provided a surprisingly effective counter to the devastating impact of the stone balls. Like stones thrown into mud, the cannonballs were smothered, their force neutralized.

As their own artillery was poorly situated for firing heavy balls, the defenders reinvented the pieces as huge shotguns, packing each cannon with five or 10 lead balls the size of walnuts. Fired at close range, the effect was appalling:

[They had] immense power in penetrating and perforating, so that if one hit a soldier in armor, it went straight through both his shield and body, then through another behind who was in the line of fire, and then another, until the force of the powder was dissipated. With one shot, two or three men could be killed at the same time.

Hit by this withering fire, the Ottomans suffered terrible casualties. But to Mehmed, men were a cheap and expendable resource.

On April 18, the sultan judged that his gunners had punched enough holes in the walls to launch a major assault. It failed, with a huge loss of life, but there was no respite; his big guns went on firing. Cannons had been used in siege warfare before, but what was unprecedented about Mehmed’s bombardment was its intensity and duration. No other army in the world possessed the materials required to mount a continuous artillery bombardment on this scale. The guns blasted away day and night, and chunks of wall continued to collapse.

For the defenders, the unceasing cycles of bombardment, attack and repair began to blur. Like later diaries of trench warfare, the chroniclers’ accounts become repetitive and monotonous. “On the 11th of May,” recorded a defender, “nothing happened either by land or at sea except a considerable bombardment of the walls from the landward side….On the 13th of May, there came some Turks to the walls skirmishing, but nothing significant happened during the whole day and night, except for continuous bombardment of the unfortunate walls.” This pattern gradually drained the defenders of energy and morale. By May 28, the guns had been firing continuously for 47 days, expending 55,000 pounds of gunpowder and delivering an estimated 5,000 shots. Gunners had blasted nine substantial holes in the outer wall, only to be replaced piecemeal by the earth stockade. Both sides were exhausted.

Mehmed knew the time had come: On May 29, 1453, he ordered a climactic full-scale assault. At 1:30 in the morning, to the beating of drums and clashing of cymbals, the Ottoman army rolled forward along the whole four-mile sector. Behind them the cannons put up a withering fire. Volleys of stone shot sprayed the walls, peppering the defenders and felling Ottoman troops from behind. The extraordinary noise of the battle was so deafening that, according to one defender, “the very air seemed to split apart….It seemed like something from another world.”

After several hours of confused fighting, one of the big cannons landed a direct hit on the stockade and opened a hole. Dust and cannon smoke obscured the front line, but Ottoman troops moved quickly into the breach. Mehmed’s men soon overwhelmed the defenses and sacked and burned the city in a few hours of terrible massacre.

Mehmed had succeeded where all previous Ottoman attempts had failed, and it was the big guns that made the difference. The fall of Constantinople symbolized the end of outmoded medieval techniques of castle construction and siege warfare and opened a terrible new chapter in military history. The use of massed artillery bombardment would prevail all the way to the battlefield of the Somme and beyond.

Mehmed lies buried in a mosque complex in the city he captured. At the door of his tomb stands a stone cannonball.

For further reading, Roger Crowley recommends his own 1453: The Holy War for Constantinople and the Clash of Islam and the West and The Fall of Constantinople, by David Nicolle, Stephen Turnbull and John Haldon. Or listen to a radio discussion on the subject in the BBC audio archives at [].

This article was written by Roger Crowley and originally published in the September 2007 issue of Military History Magazine. For more great articles, subscribe to Military History magazine today!