Fall of Constantinople , (May 29, 1453), conquest of Constantinople by Sultan Mehmed II of the Ottoman Empire . The dwindling Byzantine Empire came to an end when the Ottomans breached Constantinople’s ancient land wall after besieging the city for 55 days. Mehmed surrounded Constantinople from land and sea while employing cannon to maintain a constant barrage of the city’s formidable walls. The fall of the city removed what was once a powerful defense for Christian Europe against Muslim invasion, allowing for uninterrupted Ottoman expansion into eastern Europe .

In the meantime, Byzantine Emperor Constantine XI Palaeologus entreated major powers in Christendom to aid him in the impending siege. Hungary refused to assist, and, instead of sending men, Pope Nicholas V saw the precarious situation as an opportunity to push for the reunification of the Orthodox and Roman Catholic churches, a priority of the papacy since 1054. Orthodox leaders voted in favour of union, but the people of Constantinople were adamantly against it and rioted in response. Military support came from Venice and Genoa. An Ottoman attack on a Venetian ship in the Bosporus prompted the Venetian Senate to send 800 troops and 15 galleys to the Byzantine capital, and many Venetians presently in Constantinople also chose to support the war effort, but the bulk of the Venetian forces were delayed for too long to be of any help. For Genoa’s part, the city-state sent 700 soldiers to Constantinople, all of whom arrived in January 1453 with Giovanni Giustiniani Longo at their head. Emperor Constantine XI named Giustiniani commander of his land defenses and spent the rest of the winter strengthening the city for a siege.

Now sultan for the second time, Mehmed II intended to complete his father’s mission and conquer Constantinople for the Ottomans. In 1452 he reached peace treaties with Hungary and Venice. He also began the construction of the Boğazkesen (later called the Rumelihisarı ), a fortress at the narrowest point of the Bosporus , in order to restrict passage between the Black and Mediterranean seas. Mehmed then tasked the Hungarian gunsmith Urban with both arming Rumelihisarı and building cannon powerful enough to bring down the walls of Constantinople. By March 1453 Urban’s cannon had been transported from the Ottoman capital of Edirne to the outskirts of Constantinople. In April, having quickly seized Byzantine coastal settlements along the Black Sea and Sea of Marmara , Ottoman regiments in Rumelia and Anatolia assembled outside the Byzantine capital. Their fleet moved from Gallipoli to nearby Diplokionion, and the sultan himself set out to meet his army.

In contrast to the Byzantines, the Ottoman Turks had extended their control over virtually all of the Balkans and most of Anatolia , having conquered several Byzantine cities west of Constantinople in the latter half of the 14th century. Constantinople itself became an Ottoman vassal during this period. Hungary was the primary European threat to the Ottomans on land, and Venice and Genoa controlled much of the Aegean and Black seas. Sultan Murad II laid siege to Constantinople in 1422, but he was forced to lift it in order to suppress a rebellion elsewhere in the empire. In 1444 he lost an important battle to a Christian alliance in the Balkans and abdicated the throne to his son, Mehmed II. However, he returned to power two years later after defeating the Christians and remained sultan until his death in 1451.

By the mid-15th century, constant struggles for dominance with its Balkan neighbours and Roman Catholic rivals had diminished Byzantine imperial holdings to Constantinople and the land immediately west of it. Furthermore, with Constantinople having suffered through several devastating sieges, the city’s population had dropped from roughly 400,000 in the 12th century to between 40,000 and 50,000 by the 1450s. Vast open fields constituted much of the land within the walls. Byzantine relations with the rest of Europe had soured over the last several centuries as well: the Schism of 1054 and the 13th-century Latin occupation of Constantinople entrenched a mutual hatred between the Orthodox Byzantines and Roman Catholic Europe. Nevertheless, just as deeply entrenched was the understanding that Byzantine control of Constantinople was a necessary bastion against Muslim control of land and sea in the eastern Mediterranean .

Battle

In the 15th century, Constantinople’s walls were widely recognized as the most formidable in all of Europe. The land walls spanned 4 miles (6.5 km) and consisted of a double line of ramparts with a moat on the outside; the higher of the two stood as high as 40 feet (12 metres) with a base as much as 16 feet (5 metres) thick. These walls had never been breached in the thousand years since their construction. An adjoining sea wall ran along the Golden Horn and the Sea of Marmara, the latter section being 20 feet (6 metres) high and 5 miles (8 km) long. When combined with a large metal chain that had been drawn across the Golden Horn, Constantine was confident that the city’s defenses could repel a naval assault and withstand Mehmed’s land forces until relief came from Christian Europe. However, Constantine’s capacity to defend his city was hampered by his small fighting force. Eyewitness Jacopo Tedaldi estimates a presence of 30,000 to 35,000 armed civilians and only 6,000 to 7,000 trained soldiers. Giustiniani intended to concentrate most of these men at the land walls to the north and west, the centre of which he observed to be the most vulnerable section of the city. A small fleet of naval and armed merchant vessels were also stationed in the Golden Horn to defend the chain. However, without outside support, Constantinople’s defenders would be spread thin.

The Ottoman besiegers vastly outnumbered the Byzantines and their allies. Between 60,000 and 80,000 soldiers fought on land, accompanied by 69 cannon. Baltaoğlu Süleyman Bey commanded a fleet stationed at Diplokionion with an estimated 31 large and midsize warships alongside nearly 100 smaller boats and transports. Mehmed’s strategy was straightforward: he would use his fleet and siege lines to blockade Constantinople on all sides while relentlessly battering the walls of the city with cannon. He hoped to breach them or otherwise force a surrender before a Christian relief force could arrive.

On April 6 the Ottomans began their artillery barrage and brought down a section of the wall. They mounted a frontal assault of the land walls on April 7, but the Byzantines repelled them and were able to repair the defenses. After pausing to reposition his cannon, Mehmed reopened fire and thereafter maintained daily bombardment.

On April 12 the sultan dispatched a contingent of troops to subdue two nearby Byzantine forts and ordered Baltaoğlu to rush the chain. The fleet was twice driven back, and Baltaoğlu retreated to Diplokionion until the night of the 17th, when he moved to capture the Princes Islands southeast of the city at the same time that Mehmed’s land regiments assaulted the Mesoteichon section of the wall. Constantinople’s defenders once again held their ground, however, and Baltaoğlu’s success at the islands was irreparably marred by the revelation that three relief ships from the pope and one large Byzantine vessel had nearly reached the city unhindered. The Ottoman galleys were too short to capture the tall European warships, and, with the help of the Golden Horn fleet, the warships safely sailed past the chain. Upon hearing of his navy’s defeat, Mehmed stripped Baltaoğlu of his rank and arranged for his replacement.

Mehmed was determined to take the Golden Horn and pressure the Byzantines into submission. He angled one of his cannons such that it could strike the defenders of the chain and then began to construct an oiled wooden ramp upon which he intended to portage his smaller vessels from the Bosporus to the Golden Horn. By April 22 the ships had circumvented the chain in this way and, barring the chain itself, seized control of all the waters surrounding the city. The defenders attempted to attack the remainder of the Ottoman fleet in the Bosporus, but they were defeated.

Having encircled Constantinople in full, Mehmed continued his artillery barrage of the land walls through May 29. The Ottoman cannon created several breaches, but most were too narrow to send troops through. The city’s defenders continued to repair the walls at night and reinforced areas at the damaged Gate of St. Romanus and the Blachernae sector. In the early hours of May 29, Ottoman labourers filled the moat surrounding the city. Just before dawn, the sultan launched a coordinated artillery, infantry, and naval assault on Constantinople. Two attempts to rush the Gate of St. Romanus and the Blachernae walls were met with fierce resistance, and the Ottoman soldiers were forced to fall back. Mehmed ordered a third attack on the gate, this time with one of his own palace regiments of 3,000 Janissaries. A small group reached the top of a tower through another gate but were nearly eliminated by the defenders until Giustiniani was mortally wounded by Ottoman gunfire while on the ramparts. He was carried to the rear, and his absence sowed confusion and lowered morale among the ranks. This allowed the sultan to send in another Janissary regiment and take the inner wall at the Gate of St. Romanus.

A rout of the defenders ensued, with many of the Venetian and Genoese fighters retreating to their ships in the Golden Horn. Emperor Constantine XI is reported to have been killed while either fighting near the breach or fleeing to an escape boat. Although the sultan attempted to prevent a total sack of the city, he permitted an initial period of looting that saw the destruction of many Orthodox churches. When most of Constantinople was secure, Mehmed himself rode through the streets of the city to the great cathedral of Hagia Sophia, the largest in all of Christendom, and converted it into the mosque Ayasofya. He stopped to pray and then demanded that all further looting cease immediately. The sultan thus completed his conquest of the Byzantine capital.