Many associate the end of the Roman Empire with the sack of Rome in 476 AD. However, only half of the Roman Empire actually fell. By 476, the Empire existed as separate eastern and western entities. The Eastern Roman Empire continued for another 1,000 years though today we call it the Byzantine Empire. The Byzantines had their share of good and bad emperors and over time their influence grew and shrank. One factor sustained the Eastern Empire through good times and bad: the towering walls of its capital, Constantinople. Without those defenses, the Byzantine Empire likely would not have lasted more than 200 years beyond the Western Empire. The last remnant of the Byzantine Empire came crashing down with its walls in 1453 ending an era and ushering in a new form of warfare.

Eastern and Western Roman Empires

In some ways separating the Roman and Byzantine Empires is misleading. After 476 AD, those in the East still thought of themselves as Romans acclaiming Constantinople the new Rome. German historian Hieronymus Wolf brought “Byzantine” into use through his influential 1557 history: Corpus Historiae Byzantinae. Wolf elected to call the Eastern Empire by an ancient Greek name Byzantium, derived from the Greek town on the Bosporus Strait preceding Constantinople. The new designation created a somewhat artificial delineation, though it was not illogical. There were significant differences between East and West beyond geography.

Diocletian divided the Empire into eastern and western entities in 285-6 AD. Constantine reunited the two halves in the 4th century, founding Constantinople and legalizing Christianity. Theodosius I decreed Christianity as the official religion of the entire Empire though his death in 395 caused the Empire to split again, this time permanently. Even before Christianity became the official imperial religion, differences existed across regions over secular and spiritual matters. In the West, the Bishop of Rome had always been the leader of the Church in Italy, but easterners did not acknowledge the supremacy of Rome. Early Christians also differed on fundamental issues of faith and doctrine that grew into the Great Schism of 1054 where the western Catholic and eastern Orthodox Churches went their separate ways.

Additionally, Emperor Heraclius (610-641) adopted Greek over Latin as the official Byzantine language and restructured imperial administration towards a more Hellenic model. Finally, the Eastern Empire developed its own distinctive architectural and artistic preferences reflecting Hellenic and Middle Eastern cultural influences. These differences evolved gradually over the course of centuries. For the Byzantines themselves there was no time where they stopped identifying as Roman, but Wolf’s decision to use a Greek term to highlight the differences name made sense.

Byzantine Enemies and the Measures Taken to Thwart Them

In the succeeding centuries, rivals including the Sassanids, Arab Muslims, Normans, Germanic Crusaders, Slavs and others came and went. The empire waxed and waned from the time of Justinian (527-565) to the 1300s when the Ottoman Turks came on the scene. After subjugating the Serbs in the Battle of Kosovo in 1389, the Ottomans turned their sights on Constantinople and the tottering Byzantine Empire. By the 1400s, the Ottomans and others had picked apart the Byzantine Empire until it was a shell of its former self. Byzantine hegemony included little more than the city of Constantinople itself. Once the world’s largest city boasting a population of 500,000, by 1450 Constantinople was reduced to a mere 40,000.

The Byzantines still retained one advantage: the walls of their capital. Constantine built the first city wall at its founding circa 330 AD. A century later, Theodosius II constructed new and more formidable fortifications. His new wall was 36 feet tall with a thickness of 25 feet studded with at least 94 towers large enough to hold artillery machines. Not satisfied with a single obstacle, Theodosius added two more walls. The second wall was 25 feet in height and 6 feet thick. The third wall was smaller but the inner walls and towers were aligned to create integrated fields of fire. As a final touch, Theodosius dug a wide moat at the base of the outermost wall.

Constantinople was also ideally situated on hills that accentuated the height of the walls. Built on a peninsula, the city could not be easily surrounded. Additional walls with almost 300 towers protected the shores. The inhabitants could hold out behind their stone fortifications indefinitely receiving shipments of food and aid by sea. Over the next 1,000 years, the design proved its worth withstanding 22 separate sieges.*

Mehmet II Comes to Power as the Ottoman Sultan with Visions of Empire

Ottoman ruler Mehmet II rose to power in 1449 with dreams of capturing Constantinople and he inherited a large army and the treasury to do it. History had proven a large army and money alone were not enough. Mehmed was not the first Muslim leader with such ambitions. Two other Muslim rulers had laid siege in 674 and 717. Both ended in disaster but made Constantinople the most prized of conquests. “Many martyrs had perished at [Constantiople’s] walls . . . . Their deaths designated the city as a holy place for Islam and imparted a messianic significance to . . . its capture.” (Crowley, p. 14).

By the 1300s the energy of jihad that drove Muslims to conquer new lands had passed from the Arab Abbasid and Umayyad Caliphates to the Ottoman Turks. Muslim scholar Mahmud Al Kashghari wrote: “God caused the sun of empire to rise in the mansions of the Turks . . . and gave them sovereignty, and made them kings of the age, and placed the reins of the people of this time in their hands . . .It is incumbent on every man of sense to rally to them.” (Lewis, p. 207-208).

In 1422, Mehmet’s father, Murad II made a third Islamic attempt to capture Constantinople. He “appeared like a cloud full of hail and ruinous destruction . . . [casting] a shadow over each and every part of the land . . . and like a blaze of scorching lightning . . . [he] set fire to everything and reduced it to ashes.” (Canasus). The Ottomans had cannon by this time and a “legion of other war engines of every kind” (Canasus) and they targeted a tower which “had fallen into disrepair and was full of cracks from top to bottom.” (Canasus). “Seventy shots from the largest cannon struck that dilapidated tower and caused no harm.” (Canasus). The Byzantine defenders remained safe inside their walls until the siege fell apart. A rebellion by Murad’s brother forced the Ottomans to retire.

As soon as he became sultan in 1449, Mehmet made preparations to capture Constantinople. He seized control of the shipping lanes in the narrow Bosporus Straits building a fort at one end named Bogaz Kesen (“throat cutter”). To fulfill the messianic vision of capturing Constantinople, however, Mehmet needed something new that his father and other previous invaders lacked to get past Theodosius’ walls.

Orban Offers a Solution

In 1452, Hungarian mercenary Orban (sometimes called “Urban”) came to Constantinople. With wars raging across Europe and the Middle East, there were no shortage of professional soldiers willing to fight for the highest bidder. Orban was no ordinary mercenary. He did not pick up a sword and join the ranks of infantry, he had specialized technical skills. Orban could forge the most advanced weapons of the 15th century, the cannon and the bombard.

Gunpowder was still new to Europeans and its uses had still not been fully realized. Invented by the Chinese in circa 850 AD, gunpowder made its way along the Silk Road to the West by the 14th century. There are conflicting accounts of how and when gunpowder became a factor in Europe. The French and English may have first employed cannon in Europe in the Hundred Years War, but they were still exotic and not widely understood. Firearms and cannon were primitive, slow to load and unreliable. Orban likely received his training from Germans who brought cannon forging technology to the myriad conflicts in Eastern Europe of the early 1400s. Through their own campaigns in Eastern Europe, the Ottomans had become acquainted with firearms and cannon as well.

Orban went first to Byzantine Emperor Constantine XI in 1452 and offered to cast massive bronze cannon called bombards. The Emperor expressed interest and gave Orban a stipend to keep him in Constantinople while the Byzantines tried to come up with funds to hire workers and purchase the huge quantity of expensive metals and gunpowder ingredients necessary for the bombards.

Ultimately Constantine was unable to raise so much coin. In the end, a depopulated Constantinople lacked sufficient resources. With almost no outside territory remaining, the Byzantine Empire simply could not afford the luxury of bombard cannon. His treasury was so depleted, Constantine could not even pay Orban’s stipend regularly.

After a year, Orban grew tired of waiting and left Constantinople offering his services to the surging Ottomans. Sultan Mehmet II had plenty of money and access to the raw materials needed. He asked Orban if a cannon powerful enough to penetrate the thick walls of Constantinople could be forged. Orban confidently assured the sultan that he could fill the order: “I have examined the walls of the city in great detail. I can shatter to dust not only these walls . . . but the very walls of Babylon itself.” (Crowley, p. 90). Mehmet immediately hired Orban stipulating that he wanted to see the first gun in action before paying for more.

Orban constructed furnaces with baffles to melt the bronze. The charcoal had to burn continuously for days constantly re-fueled and stoked to reach temperatures sufficient to melt metal. Once the furnaces were hot enough, metals scraps were thrown into large crucibles. The work was dangerous given the high temperatures and toxic fumes. The metal was superheated for three days using baffles until the molten metal attained the right reddish orange tone. The furnaces were opened and molten bronze flowed through a channel into clay molds dug into the ground. Workers had to be skilled in the use of long poles to eliminate bubbles in the molten stream which could cause the bombard to explode when fired. Once cast, Orban’s workers packed the mold in wet sand to slow cooling so the bronze would not crack.

After days of cooling, workers extracted the new bombard from the pit. Chipping away the clay molding revealed a true monstrosity. The first bombard was 27 feet long with an 8 inch thick barrel and a 30 inch maw capable of firing round stone balls weighing up to 1500 lbs. The barrel came in two parts to be assembled with large screws. Orban named his creation “Basilica.”

After weeks of work, Basilica finally fired. A massive stone ball erupted from the barrel with a great flash, shaking the ground and soaring more than a mile before burrowing 6 feet into the ground. Mehmet was well pleased. Orban began forging other bombards (none as big as Basilica) with smaller supporting cannon. In addition to supplying the bronze needed, Mehmet began amassing gunpowder and shaping stone boulders into cannon balls. In all, Orban produced 69 cannon and bombards to fill out 14-15 batteries. Each battery had one bombard able to fire 700-1,500 lb. projectiles supported by 3 or four smaller cannon which launched balls weighing up to 200 lbs.

Mehmet Marches on Constantinople

With the cannon and bombards completed, Mehmed began his campaign. Just moving Basilica required several carts bound together, 200 men and 60 oxen. 50 carpenters and 200 assistants went ahead to construct wooden bridges to ford rivers and uneven places in the road. Even with all that muscle, the cannon transports travelled only 2.5 miles a day. It took 6 weeks to reach Constantinople. Mehmet’s army of 100,000 or more** marched ahead to establish a siege line.

Byzantine sentinels first sighted the Ottomans on April 2nd, the day after Easter. Soon “the air seemed like a forest because of [the massed] lances.” (Crowley, p. 95 quoting Turkish historian Tursun Bey). When the army camped, “the earth could not be seen for the tents.” (Ibid). By the time the cannon arrived, the Ottomans had dug a trench at a distance of 250 yards around Constantinople’s walls with emplacements for the cannon. Mehmet erected his large red and gold tent in the center opposite the Lycus Valley directly behind Basilica’s emplacement. The Lycus Valley was a section where the walls dipped significantly and the Byzantines lost the advantage of the added height of hills. This section was the most obvious choice to create a breach and had been targeted by besiegers in the past.

Placing the cannon required a lot of preparation. Emplacements had to be protected because loading the heavy stone balls required time and a block and tackle and a wooden ramp. The Ottomans built a wooden screen in front of each cannon with a hinged door that remained closed to protect the gunners as they loaded. When ready to fire, soldiers opened the door. For several days the Byzantines heard the ominous sounds of an army laying siege: hammers pounding, axes chopping, shovels digging, the grunts and whinnies of laboring animals and men, shouted commands and Muslim calls to prayer. The Byzantines only had about 7,000 defenders, insufficient numbers to defend both the inner and outer walls. Constantine had no hope of breaking the siege. The Byzantines would have to hold out long enough for help to arrive from Europe or for some mishap like typhus or other plague to take hold in the Ottoman camp. However, so long as the walls remained intact, the badly outnumbered Christians had a fighting chance.

By April 6, 1453, only a few smaller cannon had arrived. The Ottomans fired several rounds to no effect and launched an enthusiastic but foolish infantry assault that resulted in heavy casualties. Mehmet had tested the Christians’ resolve and recognized he had a fight on his hands. Rather than renew the attack, the sultan chose to wait for the arrival of the bombards.

Basilica and the Bombards Begin Their Destructive Work

Mehmet’s bombards and cannon were finally in place and loaded by April 12th. The cannon began firing simultaneously. The opening barrage generated a “terrifying roar and a violent shaking of the ground beneath for a great distance and a din such as has never been heard.” (Crowley, p. 113). The sound and tremor could be felt throughout the city all the way to the ships in the Bosporus. The great stone balls stuck the walls cracking and demolishing them and exploding into fragments “dealing death to those standing nearby.” (Ibid.)

Basilica could only be fired seven times a day and had to be cleaned thoroughly and cooled with olive oil after each firing. As might be imagined, reloading a 1,500 lb. cannonball took a long time as well. Gunpowder was tightly packed into the back of the cannon with a sheepskin wad so that the cannonball rested tightly against the gunpowder charge. Even with limited use, Basilica cracked after a few days of use. Orban added iron bands which worked for a while, but the bombard soon became unusable. Even though Basilica was out of action, the other bombards and cannon did devastating work on Theodosius’ walls. Mehmet ordered the cannon to be fired day and night to create a major breach as soon as possible.

After a few days, the Ottomans discovered an effective strategy to increase the effect of their stone projectiles by firing in a triangular pattern. Two smaller cannon hit the wall several yards apart. Then a bombard fired below the other two shots. With the wall weakened by the first two shots, the third larger cannonball caused large chunks of the wall to collapse. In the past, besieged Byzantines could repair damage as it occurred. Ottoman cannonballs caused much more destruction. At first the Byzantines minimized the damage by pouring a quick drying lime solution down the walls to fill cracks, but the constant bombardment was too much. 2,000 years of amassed knowledge on siege defense was suddenly obsolete. As the walls collapsed, makeshift stockades of barrels filled with rock and earth served as a replacement. Over time large sections of the walls disappeared to be replaced by less defensible stockades.

As the bombards and cannon relentlessly opened new holes, Ottoman infantrymen began dragging trees, rocks, dirt, and debris to fill the moat. At close range, the defenders inflicted heavy casualties, but by April 18th the Ottomans had sufficiently filled moat in front of the Lycus Valley for Mehmet to attempt a major assault.

The barrage continued all day on the 18th “intermingled with shots from the rifles and crossbows [from Ottoman infantrymen] whenever and wherever an enemy exposed himself.” (Phrantzes) At “about nine o’clock [pm] suddenly big drums, cymbals horns and zournes [pipes] echoed through the Turkish camp along the whole line, and masses of Turkish warriors advanced with loud shouts towards the walls.” (Ibid).

As the Ottomans closed, both sides fired guns, crossbows, arrows. Ottoman attackers and Christian defenders clashed at the walls raising a great din. Hand to hand fighting broke out in the forward ranks as those further back continued firing. “The reports of rifles, the ringing of bells, the clash of arms, the cries of fighting men, the shrieks of women and wailing of children produced such a noise, that it seemed as if the earth trembled. Clouds of smoke fell upon the city and the camp, and the combatants at last could not see each other.” (Ibid).

Mehmet broke off his attack a little after midnight and his soldiers limped back to camp exhausted leaving their dead and wounded on the field. The Christian defenders slumped where they stood with many falling into a deep sleep. Making the rounds of his defenses, Constantine had difficulty rousing his sentinels. A chilling silence fell over the battlefield, broken only by the plaintive cries of the wounded.

In spite of the failure, Mehmet ratcheted up the pressure. The Byzantines had blocked access to the Bosporus chnnel with a heavy chain stretched across the Bosporus. Ottoman sailors bypassed the chain by carrying a fleet of war galleys across land into the Black Sea forcing Constantine to thin his already undermanned land wall defenses to garrison the sea walls. The Ottomans began launching surprise attacks at different points to wear down the defenders who were beginning to run short of food and supplies. Gaps in the walls and collapsed towers made defense more difficult.

Every Ottoman assault was repelled, but each made progress. On May 12th, a portion of the wall collapsed and Ottoman cavalry rushed through the breach before the defenders could react. The horsemen fought their way into the streets of Constantinople. Only the timely arrival of Constantine and his personal retinue saved the day. Nevertheless, every day Constantinople had fewer defenders and larger gaps to defend.

Mehmet altered his strategy focusing more guns on specific points on the walls to open larger breaches. He also authorized the digging of tunnels to undermine the walls. Thanks to the skills of a Scots siege expert named John Grant, all 14 of Mehmet’s tunnels were intercepted and destroyed before they could cause damage.

Mehmet had not exhausted every option though. On the morning of May 16th, siege towers higher than the walls appeared out of nowhere before Constantinople’s ditch. Crossbowmen and gunners fired all day from the apex as men at the bottom of the tower threw dirt, trees and other debris into the ditch. Constantine recognized the siege towers were a mortal threat and that night his men rolled lighted barrels of gunpowder at several towers blowing them up. The Byzantines sallied forth and killed the survivors. Mehmet was compelled to withdraw the surviving towers. Though the tunnels and towers failed, they placed ever greater pressure on the besieged Christians who never knew from where the next attack would come.

Final Preparations for One Last Great Assault

By May 26th, a crisis of confidence existed in both camps. The Byzantines were now well aware that no relief would be coming from Europe. They remained under constant barrage worked to exhaustion countering Ottoman tunnels and walls. Exerting energy to hold the Ottomans at bay weakened the defenders’ efforts to maintain repairs on the walls which continued be subjected to bombardment night and day. The growing hunger and unrelenting pressure took a toll. Christian factions within the city began quarreling amongst themselves. In the Ottoman camp, the soldiers grumbled about seven weeks of siege with no end in sight as thousands of their number were sacrificed attacking the seemingly impregnable defenses.

Mehmet called his commanders together and exhorted them with Islamic verse. Constantinople was a “bone in the throat of Allah” (Crowley, p. 139) preventing the spread of Islam into Europe. He reminded them of an old and often quoted prophesy: “In the Jihad against Constantinople, one third of Muslims will allow themselves to be defeated which Allah cannot forgive; one third will be killed in battle, making the wondrous martyrs; and one third will be victorious.” (Crowley, p. 163).

Mehmet’s plan was simple, an all-out continuous attack where division after division would be thrown at the walls until the defenders collapsed or the Ottomans were all dead. In preparation, his men lit torches and fires to illuminate their camp. Christian defenders watched as lights began expanding in a circular fashion throughout the Ottoman camp finally lighting the entire plain. For the Byzantines, the spectacle was an omen of the disaster that was to come.

On May 27th, all the large bombards were concentrated on the Lycus Valley portion of the wall and fired without regard to their possible destruction due to overuse. Mehmet rode through his camp exhorting his men promising glory and riches from the spoils of victory. Great cheers arose from the Ottoman soldiers that could be heard by the Christian defenders heightening anxiety.

In several places, Ottoman cannon and bombards had opened gaps as wide as 30 yards. Sensing an eminent final battle, bells rang continuously in Constantinople as even monks, nuns, women and children began hauling debris and assisting in repairing the ad hoc defenses. By this point, it took the effort of the entire city to replace the lost portions of the walls with stone, dirt and wood. Between labors, icons were paraded. Christians of every rank attended church services ardently praying for salvation. Constantine had only half of the original force of 7,000 remaining to defend the entire perimeter. He made his own final appeal on May 28th. Praising all in attendance for enduring the difficult 53 days of siege, Constantine called for unity and bravery which would be rewarded by God’s continued protection and blessings.

At 1:30 am on May 29th, Mehmet sent his least skilled, lightly armed auxiliaries in to wear down the defenders. The Christians cut them down with crossbows and arquebuses. Those who reached the walls were pelted with boulders, burned with hot oil and pitch and hacked to bits. As the auxiliaries fell back, Mehmet stationed his Janissaries in their path threatening and killing anyone who retreated. After 2 hours, Mehmet finally relented and allowed the few surviving auxiliaries to return.

At 3:30 am, the main assault began. Heavily armored Ottoman regulars charged. They endured the same fire, crossing over the bodies of the dead piled up against the barricades. Fighting was close quarters, desperate hand to hand battles. After two more hours of fighting though, the Turks had failed to breach Constantinople’s defenses.

Mehmet played his last card. He personally led his elite Janissaries to the wall. With a great cry the Sultan’s best troops charged using hooked sticks to pull down stockade barrels and ascending ladders under heavy fire. Constantine and his personal retinue joined the fighting. Both sides had committed everything to this final battle.

The outnumbered Christians fought magnificently and bravely but in the end, they were overwhelmed. After an hour, the defenders waivered and part of their line collapsed. The breach was like the breaking of a dam. The barricades had offset the Christian’s lack of numbers, but once the Turks began breaking through in numbers, the battle was over. Constantine XI was last seen with his most loyal aides fighting desperately even as the flood of Janissaries overwhelmed the city’s defenses. By dawn, Mehmet stood before the ruins of the walls of Theodosius as the Ottoman banner rose with the sun over Constantinople.

Conclusion

The capture of Constantinople would not have been possible without Orban’s cannon and bombards. They had reduced the greatest and most storied walls in history to rubble. The last vestige of the Roman Empire and the last tie to the Ancient World came crashing down with the walls of Constantinople. The Ottoman Empire had arrived as a major power. Mehmet was only 21 and just beginning to spread his influence. The Turks would follow their success in Constantinople with campaigns into Eastern Europe and the Mediterranean. An Ottoman army even invaded Italy in 1481. The death of Mehmet early in the campaign caused the effort to fall apart and may have saved Rome from suffering Constantinople’s fate. The Ottomans remained a potent force though for the next 200 years.

Further, the siege presaged a end to medieval stalwarts: fortified walls, armored knights and edged weaponswhich gradually gave way to artillery and massed infantry with firearms. Earthen trenches replaced stone walls and towers. Dirt absorbed the force of cannonballs far better. Armies became larger and more uniform. Firearms required less training than the time needed to become proficient wielding a sword and shield. A new emphasis on guns and cannon led to innovations that made them easier to use, more reliable and more lethal.

As with many historical events, the fall of Constantinople was not the sole event in the transformations described above, but the Ottoman victory signaled a significant shift in how history unfolded.

*Christians of the Fourth Crusade surprised the Byzantines sacking Constantinople in 1204 but did so by breaking down a gate and by overwhelming the sea walls before the surprised Byzantine defenders could adequately prepare.

** No one knows the exact number but 100,000 is conservative. At least one estimate ranges as high as 400,000.

Sources:

Gábor Agoston, Ottoman Artillery and European Military Technology in the Fifteenth to Seventeenth Centuries. Acta Orientalia Scientiarum Hungaricae 47 (1994): 15-48.

Gábor Ágoston , Firearms and Military Adaptation: The Ottomans and the European Military Revolution, 1450-1800, Journal of World History, Vol. 25, No. 1 (March 2014), pp. 85-124

John Cananus , The account of the siege of Constantinople in 1422 (1425), quoted in Purdie, Margaret. An account by John Cananus of the siege of Constantinople in 1422, University of Western Australia, Classics and Ancient History Discipline Group, School of Humanities, (2009, unpublished). https://research-repository.uwa.edu.au/en/publications/an-account-by-john-cananus-of-the-siege-of-constantinople-in-1422

(John Canasus was an eyewitness and wrote an account of Murad’s 1422 siege of Constantinople.)

Roger Crowley, 1453: The Holy War for Constantinople and the Clash of Islam and the West. New York: Hyperion (2005).

Bernard Lewis, Islam: From the Prophet Muhammed to the Capture of Constantinople. New York: Harper & Row (1974) vol. 2, 207-208.

Georges Phrantzes, The Conquest of Constantinope by the Turks. (circa 1472). https://archive.org/stream/constantinelaste00mijarich/constantinelaste00mijarich_djvu.txt

(Georges Phrantzes was an eyewitness of Mehmet’s 1453 siege and capture of Constantinople and wrote an account years later.)

William H. McNeill, The Age of Gunpowder Empires, 1450-1800. Washington, D.C.: American Historical Association, (1989).

William H. McNeill, The Pursuit of Power: Technology, Armed Force, and Society since A.D. 1000. Chicago: University of Chicago Press (1982).

All images are in the public domain and subject to fair use laws.

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