51: The Siege of Constantinople

I Take History With My Coffee Podcast
Episode: 51
Title: The Siege of Constantinople

“On the fifth of the month of April, one hour after daybreak, Mahomet Bey came before Constantinople with about a hundred and sixty thousand men, and encamped about two and a half miles from the walls of the city.”
Diary of Nicolo Barbaro, 1453

Welcome back to the I Take History With My Coffee podcast where we explore history in the time it takes to drink a cup of coffee.

Throughout the winter, preparations on both sides had reached a fever pitch.

Mehmed was deeply preoccupied with war. He spent considerable time planning strategies, sketching city defenses, and studying Western texts on fortifications and siege engines to prepare for the siege. His ability to assimilate and utilize foreign expertise was crucial for the impending attack on Constantinople. The contributions of Western advisors, particularly in siege technology, proved essential in shaping his military strategy, although some historical interpretations may exaggerate individual contributions.

Around January 1453, Mehmet called his ministers to discuss the importance of the campaign against Constantinople. In a speech recorded by Greek chronicler Kritovoulos, Mehmet highlighted the city’s historical significance in Ottoman affairs, noting its past role in fomenting civil war and disorder within the Ottoman realm. He argued that capturing Constantinople was crucial for the stability and expansion of the Ottoman Empire, stating that without it, their conquests and security would remain incomplete. Mehmet also sought to dispel the long-held belief among Muslims that the city was unconquerable, citing internal religious conflicts and weakened maritime control of the Christians. He urged his ministers to commit all available resources for a decisive attack.

In February, Ottoman troops under Karaja Bey began clearing the countryside around Constantinople, capturing or bypassing fortified outposts. By March, ships from Gallipoli were ferrying Anatolian forces into Europe.

Recognizing the importance of naval control in successfully besieging the city, Mehmet began strengthening his navy in the winter of 1452. He ordered an ambitious shipbuilding program at various shipyards, including Gallipoli, drawing on skilled shipwrights, sailors, and resources from across his empire.

The primary warship of the time was the oared galley. These vessels were long, fast, and low in the water, typically about 100 feet long, and powered by sails and oars. While formidable in calm seas, galleys had significant weaknesses, including poor seaworthiness in rough water and vulnerability to high-sided vessels.

Mehmet assembled a substantial fleet, including triremes (galleys with three tiers of oars) and smaller raiding vessels called fustae. The size of the Ottoman fleet was impressive. Experienced observers estimated it to consist of 12-18 full war galleys, 70-80 smaller fustae, 25 heavy transport barges, and various smaller vessels, totaling around 140 boats. This naval force represented a significant threat to Constantinople. It was a crucial new element in the Ottoman siege strategy, as it was the first time in seven sieges that the Ottomans had brought a fleet to attack the city.

As Mehmet made preparations, Emperor Constantine XI faced a dire situation. As we saw in the last episode, the winter of 1452-1453 was particularly harsh. But in December 1452 and January 1453, a few Italian ships managed to reach Constantinople, bringing much-needed supplies and reinforcements. News of the dire situation in the city prompted the Venetian and Genoese republics to take action. The Venetian Senate dispatched Gabriel Trevisano to escort merchant convoys from the Black Sea, bringing with him Nicolo Barbaro, who would later document these events in a detailed diary.

Concerns were mounting within the Venetian colony in Constantinople. The Venetians urgently sought to retain three merchant and two light galleys for the city's defense. During a meeting on December 14, Trevisano and other captains agreed to stay after intense negotiations and personal assurances to the emperor. Despite these efforts, on February 26, one Venetian ship and six from Crete fled, taking 700 people with them and successfully escaping to Tenedos.

Offsetting this setback was a contribution from the Genoese. On January 26, two large galleons arrived with advanced war machines and 400 well-armed soldiers led by Giovanni Giustiniani Longo, a seasoned commander. His arrival, along with 700 men in total, significantly boosted the city's morale and defensive capabilities. 
 
With the arrival of the Genoese contingent, preparations for the impending siege of Constantinople intensified. Giustiniani, an expert in siege defense, led the efforts to fortify the city's defenses. The defenders dredged the moat throughout February and March, repaired and rebuilt walls, restored battlements, and fortified inner and outer towers.

For centuries, the city's defenses symbolized its resilience, blending confidence and divine protection with practical skill. These walls remained essentially unchanged due to the static nature of siege warfare, which relied on techniques such as blockade, mining, and battering rams. Under Giustiniani’s guidance, the city's defenders worked to reinforce the walls, believing they would continue to hold as they had for centuries. They were unaware they were on the brink of a technological revolution that would drastically alter siege warfare.

Meanwhile, Mehmet was strengthening his forces, particularly in artillery. The Ottomans likely acquired gunpowder weapons around 1400 via the Balkans. Guns were first mentioned in 1313, with cannons widespread in Europe by the late 14th century. The so-called gunpowder revolution will be the subject of a future podcast.  

Ottoman interest in artillery grew around 1420 as they expanded into the Balkans.  The Ottomans were in a prime position to capitalize on advancements in artillery technology due to their self-sufficiency in crucial resources like copper and saltpeter and their ability to acquire expertise through conquest and purchase. They established efficient structures for disseminating this knowledge within their army, quickly mastering the logistical complexities of gunpowder warfare. 

Despite early ineffectiveness, Ottoman artillery improved rapidly. By the 1440s, they could cast medium-sized barrels on the battlefield. This allowed them to repair and customize cannons as needed.  By 1446, the Ottomans had refined their artillery and successfully breached the Hexamilion Wall at the Isthmus of Corinth. This coincided with advancements in European gunpowder technology, such as the development of more powerful and stable "corned" powder. 

The Ottomans' affinity for siege guns stemmed from their historical challenges with fortified settlements. Artillery offered a swift solution, and it caught the scientific interest of Mehmet II, who began experimenting with large guns early in his reign. The Byzantines also recognized the potential of gunpowder weapons but lacked the resources to invest heavily in them. Mehmed employed Orban, a Hungarian cannon founder who had initially sought employment with the Byzantines but was turned away due to their lack of funds. Mehmet tasked Orban with casting a cannon capable of breaching the walls of Constantinople. 

Orban's contribution lay in his ability to construct large-scale molds and manage the complex variables of casting. During the winter of 1452, he embarked on creating what might have been the largest cannon ever built.  In January 1453, Orban's foundry in Edirne produced an enormous cannon, 27 feet long with a 30-inch diameter, nicknamed “Basilica,” capable of firing stone balls weighing over half a ton. The cannon was successfully test-fired outside Mehmet's new palace in Edirne, sending a stone ball a mile across the countryside and burying it six feet into the ground.

Doukas, a contemporary Greek chronicler, recorded the test firing and noted its immense power. Mehmet used the cannon as a psychological and practical weapon, ensuring that reports of its formidable capabilities reached Constantinople. Meanwhile, Orban's foundry continued to produce more cannons of varying sizes, though none as significant as the initial supergun, with some measuring over 14 feet.

The Ottomans faced the significant challenge of transporting their massive artillery, including Orban's supergun, from Edirne to Constantinople. This 140-mile journey required extensive workforce and engineering. The enormous barrel was loaded onto several wagons chained together and pulled by sixty oxen. Two hundred men supported the barrel as it moved slowly over the Thracian countryside, while carpenters and laborers worked ahead to level the path and construct wooden bridges over rivers and gullies. The great gun advanced at a rate of two and a half miles per day towards the city walls.

By late March, Mehmet's forces began to gather around Constantinople. His army, estimated at around 60,000-70,000 soldiers, included sipahis (cavalry), janissaries (elite infantry), azaps (light infantry), and various artillery and engineering units. 

The first Ottoman troops were sighted outside Constantinople on April 2 after transporting heavy artillery, including a massive cannon, which required significant logistical support. Over the next few days, they systematically set up their siege positions, creating a massive encampment outside the city walls. The army was carefully organized, assigning specific positions and roles to different units. 

Inside Constantinople, Constantine conducted a census of his defenders, revealing only about 7,000-8,000 men available to defend the city's extensive walls. He kept this information secret to avoid damaging morale and organized the defense by dividing the city into sectors and assigning commanders to different sections of the walls.

Constantine faced difficult decisions when deploying his limited forces. He focused on defending the outer walls rather than the inner ones, a controversial decision criticized by some. He also tried to boost morale through shows of force and religious processions. Meanwhile, Mehmet made final preparations, moving his artillery into position and motivating his troops with promises of religious glory and plunder.

Both sides recognized the critical importance of time. Mehmet needed to act quickly before his army's enthusiasm waned or Western reinforcements arrived. Constantine's strategy was to hold out as long as possible in hopes of relief from the West. The defenders placed great hope in Giustiniani’s expertise. However, he had never faced the massive artillery bombardment the Ottomans were about to unleash. 

The defenders closed off the Golden Horn with a great chain, a defensive tactic dating back to 717. They organized their naval forces, consisting of a diverse collection of ships from various Italian city-states and Byzantine, Catalan, and Provençal vessels. The fleet included galleys and merchant sailing ships, the latter being high-sided vessels that could be effectively used in combat despite not being purpose-built warships.

The defenders arranged their largest merchantmen in front of the boom across the Golden Horn, with galleys alongside them. Additional ships were in reserve in the inner harbor, and some were scuttled to reduce fire risks. The Italian sailors, particularly those from Venice and Genoa, were confident in their maritime skills and believed they could effectively defend against the larger Ottoman fleet. 

The siege commenced on April 6 after Friday prayer. Emperor Constantine positioned himself alongside 500 Genoese soldiers at the weakest point of the defenses.

Then the bombardment began. The walls crumbled under the impact of large stone cannonballs, and the noise terrified the population. The defenders tried various methods to mitigate the damage, including hanging bales of wool and leather sheets on the walls. Mehmet's strategy was to bombard continuously and launch periodic attacks to wear down the defenders. The large cannons, however, were difficult to manage and prone to malfunction.

Despite initial terror, the defenders adapted to the bombardment. Giustiniani devised an effective method of repairing breaches using earthworks and wooden stockades. This proved surprisingly resilient against cannonballs. A bitter struggle ensued for control of the moat, with Ottomans trying to fill it and defenders clearing it each night. 

As the bombardment of Constantinople began, Mehmet deployed his fleet. It set out from Gallipoli and started going up the Sea of Marmara towards Constantinople. The journey was challenging, as the fleet had to contend with unfavorable winds and currents. 

The Ottoman fleet was first sighted on April 12, approaching against the north wind. Its impressive size and the sounds of its crew initially caused some fear among the defenders. However, upon seeing the Christian ships drawn up in battle formation, the Ottoman fleet moved to the opposite shore and later anchored at a place called the Double Columns. This began a tense period of watchfulness, with the defenders constantly on alert for Ottoman movements.

Mehmet's fleet had three main objectives: blockade the city, attempt entry into the Golden Horn, and prevent relief fleets from reaching Constantinople. Initially, the Ottoman admiral focused on patrolling the waters around the city to prevent ships from entering or leaving the small harbors on the Marmara side. The arrival of additional ships from the Black Sea, carrying supplies for the Ottoman army, seemed to signal a new phase of activity in the siege. 

The Ottoman fleet, equipped with small cannons and infantry, assaulted the Christian ships guarding the boom. However, the defenders' higher vantage points and sturdier ships repelled the Ottoman forces. Four Christian ships (three Genoese merchant vessels and one imperial transport) arrived, bringing supplies to the besieged city. Mehmet ordered his admiral to intercept these ships at all costs. A sea battle ensued, with the Ottoman fleet of about 100 ships attacking the four Christian vessels. Initially, the Christian ships held their own, aided by favorable winds. When the wind suddenly dropped, they suddenly became vulnerable.

The Ottoman forces attempted to board the Christian ships. Despite being vastly outnumbered, the Christian vessels lashed together for mutual defense and fought fiercely. The struggle lasted hours, with both sides suffering heavy losses. Just as it seemed the Ottoman forces might prevail, the wind suddenly picked up again, allowing the Christian ships to break free and sail towards the safety of the Golden Horn.

The Christian defenders saw this unexpected turn of events as divine intervention. Venetian galleys escorted the ships into the harbor while Mehmet, enraged by this humiliating defeat, ordered his fleet to withdraw. This naval victory provided a significant morale boost to the defenders of Constantinople. 

Yet Mehmet was not to be deterred. In a bold move, he ordered his forces to transport ships overland from the Bosphorus to the Golden Horn, bypassing the chain boom protecting the harbor. They were hauled up slopes using rollers, oxen, and manpower. While likely taking longer than a single day, this operation presented a surreal spectacle with flags flying and music playing. Seventy-two Ottoman ships entered the Golden Horn on April 22.  This shocked the defenders and exposed the northern side of Constantinople to attack.

By May, Constantinople’s situation was becoming desperate. Food shortages worsened, and morale plummeted. Ottoman forces intensified their bombardment, focusing on weak points such as the St. Romanus Gate and the area near the palace. They launched several major attacks, including a night assault that nearly breached the defenses before being repelled by Constantine and his forces.  Mehmet employed skilled Saxon miners to dig tunnels under the city walls, a strategy that initially caught the defenders off guard. The Christians quickly organized countermeasures, intercepting and destroying the Ottoman tunnels through various means, including flooding, smoke, and hand-to-hand combat.

Mehmed began building a bridge across the Golden Horn using barrels to facilitate troop movements. Simultaneously, he surprised the defenders by building overnight a massive siege tower near the Charisian Gate. This tower, designed to fill the defensive ditch and overtop the walls, caused great alarm among the Christians. They managed to destroy it and other similar towers using barrels of gunpowder and burning pitch. These preparations, visible to the defenders, were a stark reminder of the vast resources at Mehmet's disposal.  

The sultan attempted diplomacy urging surrender, but Emperor Constantine refused, expressing a willingness to pay tribute rather than surrender the city. This response prompted Mehmed to announce a full-scale assault set for May 29, promising his troops rewards for breaching the walls.  The Byzantine people, deeply superstitious and believing in omens, were gripped by a sense of impending doom. They interpreted various signs and portents as indicators of the empire's imminent fall, including prophecies, natural phenomena, and religious visions.

 Meanwhile, Giustiniani worked tirelessly to repair breaches in the walls, but internal disputes among Greek leaders and the poor condition of the defenses undermined his efforts. Reports of previous funds meant for repairs being misappropriated further complicated the situation, leaving the city vulnerable as the siege progressed. 

Mehmet also faced a growing morale crisis among his troops and had to decide whether to continue the siege or withdraw.  He consulted his two trusted viziers, Halil Pasha, who advocated for peace, and Zaganos Pasha, who pushed for a decisive attack. Mehmet ultimately sided with Zaganos and decided to prepare for a final assault. To boost morale and intimidate the defenders, Mehmet ordered a dramatic display of lights and sounds throughout the Ottoman camp on the night of May 26. This spectacle, visible from the city walls, had a profound psychological impact on both sides – inspiring the Ottoman troops while demoralizing the Byzantine defenders.

On May 27, he ordered a massive bombardment of the city walls to create breaches for the assault. Mehmet then held a crucial meeting with his officer corps, where he laid out the battle plan and motivated his troops with promises of wealth and glory. He emphasized the need for coordinated attacks from all sides and relentless waves of fresh troops to overwhelm the exhausted defenders.

Mehmet personally rode through the camp. He promised governorships and honors to those who distinguished themselves in battle while threatening severe punishment for cowardice. By Islamic law, Mehmet also declared that the city would be given to the soldiers for three days of plunder if it did not surrender. But he expressly ordered that the buildings and walls were to remain his property and should not be damaged once the city was captured, showing his long-term vision for Constantinople as the future capital of the empire.

On May 28, Sultan Mehmet II ordered a day of fasting, prayer, and spiritual preparation for his troops. As night fell, the Ottoman soldiers broke their fast and prepared for battle. As anticipation built within the Ottoman camp, cries for divine intervention echoed from the city. The camp was illuminated with fires and candles, creating an intimidating spectacle for the defenders. At midnight, the Ottoman forces moved silently into position while a heavy bombardment continued. Emperor Constantine XI and his faithful minister George Sphrantzes made a final inspection of the city's defenses. They observed the Ottoman preparations from a high tower in the darkness, reflecting on their lifelong friendship and the defenders' remarkable resistance over the 53-day siege.

After 47 days of bombardment, the Ottoman cannons had significantly damaged the city walls, particularly in the weaker central Mesoteichion section  near the Lycus valley between the gates of St Romanus and Charisius. The defenders constructed a makeshift stockade using timber, stones, and other materials to reinforce the damaged areas.

On the evening of May 28, the defenders took up positions along the stockade, with about 2,000-3,000 troops equipped with various weapons. The emperor and his inner circle joined them. The Ottoman forces, meanwhile, prepared for a massive assault, with Mehmet organizing his troops to attack in waves, starting with expendable irregulars.

The attack began at 1:30 AM on May 29, with cannon fire and a silent advance of irregulars. Ottoman enforcers behind them forced these troops to fight.  They suffered heavy casualties but wore down the defenders. After two hours, Mehmet sent in his more skilled Anatolian troops, who launched a fierce assault on the stockade. The defenders fought desperately, repelling multiple waves of attackers.

Around 5:30 AM, an Ottoman cannon breached the stockade, allowing 300 Anatolians to enter the enclosure. However, the defenders managed to isolate and kill all of them, temporarily pushing back the Ottoman forces.

 After initial Ottoman attacks were repelled, Mehmed committed his elite palace regiments and Janissaries to a final assault on the city's defenses. The battle intensified around dawn, with fierce hand-to-hand combat at the stockade. The Venetian Nicolo Barbaro, in his diary, described the Janissaries as attacking "like lions with such shouting and sounding of castanets that it seemed a thing not of this world." The cannons launched, according to Barbaro, twelve hundred-pound balls. And there was other gunfire and arrows. 

Despite the defenders' determination, two crucial events turned the tide in favor of the Ottomans. First, a postern gate near the Blachernae Palace was accidentally left open, allowing Ottoman troops to breach the walls. More significantly, the Genoese commander Giustiniani was seriously wounded and withdrew from the battle. His departure demoralized the defenders and created confusion in their ranks. Mehmed seized this opportunity to rally his troops for a renewed assault.

A group of Janissaries, led by a giant named Hasan of Ulubat, planted the Ottoman flag on the walls. Although Hasan was killed, more Janissaries followed, overwhelming the defenders through sheer numbers. Nicolo Barbaro summed up the moment in his diary: "When their flag was raised and ours cut down, we saw that the whole city was taken, and that there was no further hope of recovering from this."

Panic spread among the Christian forces as Ottoman troops poured into the city. The defenders, trapped in the narrow space between walls, were massacred or crushed as they desperately tried to escape through locked gates.  The last Byzantine emperor, Constantine XI, was last seen fighting alongside his loyal retinue before disappearing into the chaos. 

With news of Constantine's possible death, the Ottomans began to pillage the city. The defenders fled to the harbor. While many managed to escape on Christian ships, the gates were eventually shut against the Turkish advance. Notable escapees included Giustiniani, who later died of grief and his wounds.

As chaos ensued in Constantinople, crowds fled to Hagia Sophia, believing that divine intervention would save them. They anticipated that an angel would empower a poor man to defeat the Turks, restoring their hope. However, when the Ottomans breached the church doors, they captured the fleeing populace, regardless of age or status, and subjected them to horrific violence and enslavement.

Sultan Mehmed II, who had remained outside the city, was informed of its fall and Emperor Constantine XI's death. He ordered a search for the emperor's body, which was identified by his distinctive shoes among the corpses. Constantine’s head was displayed on a column in the ceremonial square known as the Augusteum, symbolizing the end of Byzantine rule. 

The fall of Constantinople sent shockwaves through Christendom and marked a significant turning point in history. Mehmet would transform the city into the new Ottoman capital of Istanbul. The conquest ushered in a new era of Ottoman power and influence. The fall of Constantinople thus marked the end of the medieval Byzantine Empire and the dawn of a new age in European and Middle Eastern history.  That will be the subject of the next episode.


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