Winters on the Bosphorus can be surprisingly severe, as the Arabs had discovered during the siege of 717. The site of the city, jutting out into the straits, leaves it exposed to fierce squalls hurtling down from the Black Sea on the north wind. A particularly dank and sub-zero cold penetrates to the marrow of the bones; weeks of cheerless rain can churn the streets into mud and prompt flash floods down the steep lanes; sudden snowstorms arise as if from nowhere to obliterate the Asian shore half a mile away then vanish as quickly as they have come; there are long still days of muffling fog when an eerie silence seems to hold the city in an iron grasp, choking the clappers in church bells and deadening the sound of hooves in the public squares, as if the horses were shod in boots of felt. The winter of 1452–53 seems to have afflicted the citizens with particularly desolate and unstable weather. People observed ‘unusual and strange earthquakes and shakings of the earth, and from the heavens thunder and lightning and awful thunderbolts and flashing in the sky, mighty winds, floods, pelting rain and torrential downpours’. It did not improve the overall mood. No flotillas of Christian ships came to fulfil the promises of union. The city gates remained firmly closed and the supply of food from the Black Sea dried up under the sultan’s throttle. The common people spent their days listening to the words of their Orthodox priests, drinking unwatered wine in the taverns and praying to the icon of the Virgin to protect the city, as it had in the Arab sieges. A hysterical concern for the purity of their souls seized the people, doubtless influenced by the fulminations of Gennadios. It was considered sinful to have attended a liturgy celebrated by a unionist or to have received communion from a priest who was present at the service of union, even if he were simply a bystander to the rites. Constantine was jeered as he rode in the streets.
Despite this unpromising atmosphere, the emperor made what plans he could for the city’s defence. He dispatched envoys to buy food from the Aegean islands and beyond: ‘wheat, wine, olive oil, dried figs, chick peas, barley and other pulses’. Work was put in hand to repair neglected sections of the defences – both the land and sea walls. There was a shortage of good stone and no possibility of obtaining more from quarries outside the city. Materials were scrounged from ruined buildings and abandoned churches; even old tombstones were pressed into service. The ditch was cleared out in front of the land wall and it appears that despite their reservations, Constantine was successful in persuading the populace to participate in this work. Money was raised by public collection from individuals and from the churches and monasteries to pay for food and arms. All the available weapons in the city – of which there were far too few – were called in and redistributed. Armed garrisons were dispatched to the few fortified strongholds still held by Byzantium beyond its own walls: at Selymbria and Epibatos on the north shore of the Marmara, Therapia on the Bosphorus beyond the Throat Cutter, and to the largest of the Princes’ Islands. In a final gesture of impotent defiance, Constantine sent galleys to raid Ottoman coastal villages on the Sea of Marmara. Captives were taken and sold in the city as slaves. ‘And from this the Turks were roused to great anger against the Greeks, and swore that they would bring misfortune on them.’
The only other bright spot for Constantine during this period was the arrival of a straggle of Italian ships that he was able to persuade – or forcibly detain – to take part in the city’s defence. On 2 December a large Venetian transport galley from Kaffa on the Black Sea, under the command of one Giacomo Coco, managed to trick its way past the guns at the Throat Cutter by pretending that it had already paid its customs dues further upstream. As it approached the castle the men on board began to salute the Ottoman gunners ‘as friends, greeting them and sounding the trumpets and making cheerful sounds. And by the third salute that our men made, they had got away from the castle, and the water took them on towards Constantinople.’ At the same time news of the true state of affairs had reached the Venetians and Genoese from their representatives in the city and the Republics stirred themselves into tardy activity. After the sinking of Rizzo’s ship, the Venetian Senate ordered its Vice-captain of the Gulf, Gabriel Trevisano, to Constantinople to accompany its merchant convoys back from the Black Sea. Among the Venetians who came at this time was one Nicolo Barbaro, a ship’s doctor, who was to write the most lucid diary of the months ahead.
Within the Venetian colony in the city, concern was growing. The Venetian bailey, Minotto, an enterprising and resolute man, was desperate to keep three great merchant galleys and Trevisano’s two light galleys for the defence of the city. At a meeting with the emperor, Trevisano and the other captains on 14 December he begged them to stay ‘firstly for the love of God, then for the honour of Christianity and the honour of our Signoria of Venice’. After lengthy negotiations the ships’ masters, to their credit, agreed to remain, though not without considerable wrangling over whether they could have their cargo on board or should keep it in the city as surety of their good faith. Constantine was suspicious that once the cargo was loaded, the masters would depart; it was only after swearing to the emperor personally that they were allowed to load their bales of silk, copper, wax and other stuffs. Constantine’s fears were not unfounded: on the night of 26 February one of the Venetian ships and six from the city of Candia on Crete slipped their anchors and fled before a stiff north-easterly wind. ‘With these ships there escaped many persons of substance, about 700 in all, and these ships got safely away to Tenedos, without being captured by the Turkish armada.’
This dispiriting event was offset by one other positive contribution. The appeals of the Genoese podesta at Galata had elicited a concrete offer of help. On about 26 January two large galleons arrived loaded ‘with many excellent devices and machines for war, and outstanding soldiers, who were both brave and confident’. The spectacle of these ships entering the imperial harbour with ‘four hundred men in full armour’ on deck made an immediate impression on both the populace and the emperor. Their leader was a professional soldier connected to one of the great families of the republic, Giovanni Giustiniani Longo, a highly experienced commander who had prepared this expedition at his own initiative and cost. He brought 700 well-armed men in all, 400 recruited from Genoa, another 300 from Rhodes and the Genoese island of Chios, the power base of the Giustiniani family. Constantine was quick to realize the value of this man and offered him the island of Lemnos if the Ottoman menace should be repulsed. Giustiniani was to play a fateful role in the defence of the city in the weeks ahead. A straggle of other soldiers came. Three Genoese brothers, Antonio, Paolo and Troilo Bocchiardo brought a small band of men. The Catalans supplied a contingent and a Castilian nobleman, Don Francisco of Toledo, answered the call. Otherwise the appeal to Christendom had brought nothing but disharmony. A sense of betrayal ran through the city. ‘We had received as much aid from Rome as had been sent to us by the sultan of Cairo,’ George Sphrantzes recalled bitterly.
With the arrival of the Genoese contingent the preparations for a siege were carried forward with greater urgency. Giustiniani, who was ‘an expert in the art of wall fighting’, appraised the city’s defences with a cool eye and took appropriate measures. Under his direction, during February and March they ‘dredged the fosse and repaired and built up the walls, restoring the battlements, refortifying inner and outer towers and strengthening the whole wall – both the landward and seaward sectors’.
Despite their dilapidated condition, the city still possessed formidable fortifications. Among all the many explanations for the longevity of Byzantium, the impregnable defences of its capital city remain a cardinal factor. No city in the world owed as much to its site as Constantinople. Of the twelve miles of its perimeter, eight were ringed by sea. On the south side, the city was fringed by the Sea of Marmara, whose swift currents and unexpected storms made any sea-borne landing a risky undertaking. In a thousand years no aggressor ever seriously attempted an attack at this point. The seashore was guarded by a single unbroken wall at least fifty feet above the shoreline interspersed with a chain of 188 towers and a number of small defended harbours. The threat to this wall came not from ships but from the ceaseless action of the waves undermining its foundations. At times nature was more brutal still: in the bitter winter of 764 the sea walls were crushed by ice floes that rode up over the parapets. The whole length of the Marmara wall was studded with marble inscriptions commemorating the repairs of successive emperors. The sea ran strongly round this shoreline as far as the tip of the Acropolis point, before turning north into the calmer waters of the Golden Horn. The Horn itself provided an excellent sheltered anchorage for the imperial fleet; 110 towers commanded a single wall along this stretch with numerous water gates and two substantial harbours, but the defences were always considered vulnerable. It was here that the Venetians had driven their ships up on the foreshore during the Fourth Crusade, overtopping the ramparts and storming the city. In order to block the mouth of the Horn in times of war, the defenders had been in the habit, since the Arab siege of 717, of drawing a boom across the entrance of the Horn. This took the form of a 300-yard chain, consisting of massive cast-iron links each twenty inches long that were supported on sturdy wooden floats. With the good will of the Genoese, the chain could then be secured to a tower on the sea wall of Galata on the far side. During the winter months both chain and floats were prepared against the possibility of a naval attack.
The base of the triangle of the city’s site on the westward side was protected by the four-mile land wall, the so-called wall of Theodosius, which ran across the grain of the land from the Sea of Marmara to the Golden Horn and sealed off Constantinople from any conventional land-borne assault. Many of the most significant events in the history of the city had been played out along this extraordinary structure. It almost matched the city itself in longevity, and projected a sense of legendary immutability within the Mediterranean world. For many approaching Constantinople across the flat Thracian plains as a trader or pilgrim, an ambassador from a Balkan court or a plundering army with pretensions to conquest, the first sight of Constantinople at its apogee would be the ominous prospect of the land walls riding the gentle undulations of the landscape from horizon to horizon in a regular unbroken succession of ramparts and towers. In the sunlight the limestone walls create a facade of brilliant white, banded with horizontal running seams of ruby red Roman brick, and arrow slits similarly arched; the towers – square, hexagonal, octagonal, occasionally circular – are so close together that, as one crusader put it, ‘a seven-year-old boy could toss an apple from one turret to the next’. They rise up in successive tiers to the summit of the inner wall where the eagle banners of the emperor flutter proudly in the wind. At intervals the eye can pick out the darkness of a heavily guarded entrance to the city through which men and animals vanish in times of peace, and at the western end, close to the Sea of Marmara, a gateway panelled with flat plates of gold and decorated with statues of marble and bronze shines in the sun. This is the Golden Gate, the great ceremonial archway flanked by two massive towers of polished marble through which, in the heyday of Byzantium, emperors returned in triumph with the visible tokens of their victories: conquered kings walking in chains, recaptured sacred relics, elephants, outlandishly dressed barbarian slaves, carts piled high with booty and the whole might of the imperial army. By 1453 the gold and many of the decorations had gone but the structure was still an impressive monument to Roman glory.
The man responsible for the land wall, built to define the mature limits of the city, was not the boy Emperor Theodosius after whom it is named, but a leading statesman of the early fifth century, Anthemius, ‘one of the wisest men of the age’, for whose far-sightedness the city would owe a limitless debt of gratitude. The first line of the walls built in 413 deterred Attila the Hun, ‘the scourge of God’, from making an attack on the city in 447. When it collapsed under a severe earthquake the same year with Attila ravaging Thrace not far away, the whole population responded to the crisis. Sixteen thousand citizens totally rebuilt the wall in an astonishing two months, not just restoring Athemius’s original structure, but adding an outer wall with a further string of interspaced towers, a protecting breastwork and a brick-lined moat – the fosse – to create a formidable barrier of extraordinary complexity. The city was now protected on this side by a chain of 192 towers in a defensive system that comprised five separate zones, 200 feet wide and 100 feet high from the bed of the moat to the top of the tower. The achievement was recorded with a suitably boastful inscription: ‘In less than two months, Constantine triumphantly set up these strong walls. Scarcely could Pallas have built so quickly so strong a citadel.’
In its mature form, the Theodosian wall summarized all the accumulated wisdom of Graeco-Roman military engineering about defending a city before the age of gunpowder. The heart of the system remained the inner wall constructed by Anthemius: a core of concrete faced on both sides by limestone blocks quarried nearby, with brick courses inserted to bind the structure more firmly. Its fighting ramparts were protected by battlements and reached by flights of steps. In line with Roman practice, the towers were not bound to the walls, ensuring that the two structures could each settle at their own rate without breaking apart. The towers themselves rose to a height of sixty feet and consisted of two chambers with a flat roof on which engines to hurl rocks and Greek fire could be placed. Here the sentinels scanned the horizon unceasingly, keeping themselves awake at night by calling out to each other down the line. The inner wall was forty feet high; the outer one was lower, about twenty-seven feet high, and had correspondingly lower towers that interspaced those on the inner wall. The two walls were separated by a terrace sixty feet wide, where the troops defending the outer wall massed, ready to engage the enemy at close quarters. Below the outer wall another terrace sixty feet wide provided a clear killing field for any aggressor who made it over the moat. The brick-lined moat itself was another sixty-feet-wide obstacle, surmounted by a wall on the inner side; it remains unclear whether it was in parts flooded in 1453 or simply comprised a dry ditch. The depth and complexity of the system, the stoutness of its walls and the height from which it commanded its field of fire rendered the Theodosian wall virtually impregnable to an army equipped with the conventional resources of siege warfare in the Middle Ages.
Along its length the land wall was pierced by a succession of gates. Some gave access to the surrounding countryside via bridges over the moat, which would be destroyed in the run-up to a siege; others, the military gates, allowed connection between the different layers of the walls and were used to move troops about within the system. The wall also contained a number of posterns – small subsidiary doorways – but the Byzantines were always aware of the danger these sally ports posed for the security of their city and managed them rigorously. In general the two sets of gates alternated along the length of the wall, with the military gates being referred to by number while the public gates were named. There was the Gate of the Spring, named after a holy spring outside the city, the Gate of the Wooden Circus, the Gate of the Military Boot Makers, the Gate of the Silver Lake. Some spawned multiple names as associations were forgotten and new ones created. The Third Military Gate was also referred to as the Gate of the Reds, after a circus faction in the early city, while the Gate of Charisius, a leader of the blue faction, was also called the Cemetery Gate. And into the structure were built some remarkable monuments that expressed the contradictions of Byzantium. Towards the Golden Horn the imperial palace of Blachernae nestled behind the wall, a building said once to be of such beauty that foreign visitors could find no words to describe it; adjoining it, the dank and dismal prison of Anemas, a dungeon of sinister reputation, scene of some of the most ghastly moments in Byzantine history. Here John V blinded both his son and his three-year-old grandson, and from here one of Byzantium’s most notorious emperors, Andronikos the Terrible, already horribly mutilated, was led out on a mangy camel amongst taunting crowds to the Hippodrome, where he was strung upside down between two columns and mockingly slaughtered.
The continuous life of the wall was so long that a deep accretion of history, myth and half-forgotten association attached to the various sectors. There was hardly a place that had not witnessed some dramatic moment in the city’s history – scenes of terrible treachery, miraculous deliverance and death. Through the Golden Gate Heraclius brought the True Cross in 628; the Gate of the Spring saw the stoning of the unpopular Emperor Nicephorus Phocas by an enraged mob in 967 and the restoration of the Orthodox emperors after Latin rule in 1261 when the gate was opened from within by sympathizers. The dying Emperor Theodosius II was carried through the Fifth Military Gate in 450 following a fall from his horse in the valley outside, while the Gate of the Wooden Circus was blocked up in the twelfth century after a prophecy that the Emperor Frederick Barbarossa would use it to capture the city.
Next to St Sophia itself no structure expressed the psychic life of the city’s people as powerfully as the walls. If the church was their vision of heaven, the wall was their shield against the battering of hostile forces, under the personal protection of the Virgin herself. During sieges the constant prayers and the procession of her sacred relics along the ramparts were considered by the faithful to be generally more crucial than mere military preparations. A powerful spiritual forcefield surrounded such actions. Her robe, housed at the nearby church at Blachernae, was accorded more credit for seeing off the Avars in 626 and the Russians in 860 than military engineering. People saw visions of guardian angels on the ramparts and emperors inserted marble crosses and prayers into the outward facing walls. Near the centre point of the wall there is a simple talisman that expresses Constantinople’s deepest fear. It says: ‘O Christ God, preserve your city undisturbed and free from war. Conquer the fury of the enemies.’
At the same time, the practical maintenance of the walls was the one essential public work for the city, in which every citizen was required to help, without exemption. Whatever the state of the Byzantine economy money was always found to patch up the wall. It was sufficiently important to have its own special officials under the overall authority of the impressively named ‘Count of the Walls’. As time and earthquakes shattered towers and crumbled masonry, running repairs were marked by a wealth of commemorative marble inscriptions set into the stonework. They span the centuries from the first reconstruction in 447 to a total renovation of the outer wall in 1433. One of the last dated repairs before the siege expresses the co-operation of divine and human agencies in the maintenance of the city’s shield. It reads: ‘This God-protected gate of the life-giving spring was restored with the co-operation and at the expense of Manuel Bryennius Leontari, in the reign of the most pious sovereigns John and Maria Palaeologi in the month of May 1438.’
Perhaps no defensive structure summarizes the truth of siege warfare in the ancient and medieval world as clearly as the walls of Constantinople. The city lived under siege for almost all its life; its defences reflected the deepest character and history of the place, its mixture of confidence and fatalism, divine inspiration and practical skill, longevity and conservatism. Like the city itself, the walls were always there, and for anyone in the eastern Mediterranean, it was assumed they always would be. The structure of the defences was mature in the fifth century and changed little thereafter; the building techniques were conservative, harking back to practices of the Greeks and Romans. They had no particular reason to evolve because siege warfare itself remained static. The basic techniques and equipment – blockade, mining and escalade, the use of battering rams, catapults, towers, tunnels and ladders – these were largely unchanging for longer than anyone could recall. The advantage always lay with the defender; in the case of Constantinople its coastal position increased that weighting. None of the armies camped before the land walls had ever succeeded in effecting an entry through the multiple defensive layers, while the city always took prudent measures as a matter of state policy to keep its cisterns brimming and its granaries full. The Avars came with an impressive array of stone-throwing machinery but their looping trajectory made them far too puny to breach the walls. The Arabs froze to death in the cold. The Bulgar Khan Krum tried magic – he performed human sacrifices and sprinkled his troops with seawater. Even its enemies came to believe that Constantinople was under divine protection. Only the Byzantines themselves were ever successful in taking their own city from the land, and always by treachery: the messy final centuries of civil war produced a handful of instances where gates were flung open at night, usually with inside help.
There were just two places where the land wall could be considered potentially weak. In the central section the ground sloped down a long valley to the Lycus River and then up the other side. As the wall followed the downward slope, its towers no longer commanded the high ground and were effectively below the level occupied by a besieging army on the hill beyond. Furthermore the river itself, which was ducted into the city through a culvert, made it impossible to dig a deep moat at this point. Nearly all besieging armies had identified this area as vulnerable, and though none had succeeded, it provided attackers with a vestige of hope. A second anomaly in the defences existed at the northern end. The regular procession of the triple wall was suddenly interrupted as it approached the Golden Horn. The line took an abrupt right-angle turn outwards to include an extra bulge of land; for 400 yards, until it reached the water, the wall became a patchwork structure of different-shaped bastions and sectors, which, though stoutly built on a rocky outcrop, was largely only one line deep and for much of its length unmoated. This was a later addition undertaken to include the sacred shrine of the Virgin at Blachernae. Originally the church had been outside the walls. With a typical Byzantine logic it had been held initially that the protection of the Virgin was sufficient to safeguard the church. After the Avars nearly burned it in 626 – the shrine was saved by the Virgin herself – the line of the wall was altered to include the church, and the palace of Blachernae was also built in this small bight of land. Both these perceived weak spots had been keenly appraised by Mehmet when he reconnoitred in the summer of 1452. The right-angle turn where the two walls joined was to receive particular attention.
As they patched up their walls under Giustiniani’s direction and paraded the sacred icons on the ramparts, the people of the city could be pardoned for expressing confidence in their protective powers. Immutable, forbidding and indestructible, they had proved time and again that a small force could keep a huge army at bay until its willpower collapsed under the logistical burden of siege, or dysentery or the disaffection of the men. If the walls were decayed in places, they were still basically sound. Brocquière found even the vulnerable right angle to be protected by ‘a good and high wall’ when he came in the 1430s. The defenders however were unaware that they were preparing for conflict on the cusp of a technological revolution that would profoundly change the rules of siege warfare.