The siege was going on without end in sight. The Sultan's Vizier Halil Chandarli, had strong reservations about the siege from the beginning. He was worried about western intervention and he looked upon the whole operation with anxiety. During a meeting of the Sultan's advisors, held on May 25, the Vizir told Mehmed to raise the siege. Pursuing it might bring unknown consequences to Ottoman interests. The Sultan, also depressed because of the prolongation of the operation, finally decided to launch a grand scale final assault on the city. He was supported by younger commanders like Zaganos Pasha, a Christian converted to Islam. Halil was overruled and all present decided to continue the siege.
While the artillery continued pounding the walls without interruption, preparations for the big assault, which was to take place on Tuesday 29 May, were accelerated. Material was thrown into the foss which faced the collapsed ramparts, scaling-ladders were distributed. The Magistrates of Pera were warned not to give any assistance to the besieged. The Sultan swore to distribute fairly the treasures found in the city. According to tradition the troops were free to loot and sack the city for three days. He assured his troops that success was imminent, the defenders were exhausted, some sections of the walls had collapsed. It would be a general assault, throughout the line of the land-walls, as well as in the port area. Then the troops were ordered to rest and recover their strength.
In the city everyone realized that the great moment had come. During Monday, May 28, some last repairs were done on the walls and the stockades, in the collapsed sections, were reinforced. In the city, while the bells of the churches rang mournfully, citizens and soldiers joined a long procession behind the holy relics brought out of the churches. Singing hymns in Greek, Italian or Catalan, Orthodox and Catholic, men, women, children, soldiers, civilians, clergy, monks and nuns, knowing that they were going to die shortly, made peace with themselves, with God and with eternity.
When the procession ended the Emperor met with his commanders and the notables of the city. In a philosophical speech he told his subjects that the end of their time had come. In essence he told them that Man had to be ready to face death when he had to fight for his faith, for his country, for his family or for his sovereign. All four reasons were now present. Furthermore, his subjects, who were the descendants of Greeks and Romans, had to emulate their great ancestors. They had to fight and sacrifice themselves without fear. They had lived in a great city and they were now going to die defending it. As for himself, he was going to die fighting for his faith, for his city and for his people. He also thanked the Italian soldiers, who had not abandoned the great city in its final moments. He still believed that the garrison could repulse the enemy. They all had to be brave, proud warriors and do their duty. He thanked all present for their contribution to the defence of the city and asked them to forgive him, if he had ever treated them without kindness. Meanwhile the great church of Saint Sophia was crowded. Thousands of people were moving towards the church. Inside, Orthodox and Catholic priests were holding mass. People were singing hymns, others were openly crying, others were asking each other for forgiveness. Those who were not serving on the ramparts also went to the church, among them was seen, for a brief moment, the Emperor. People confessed and took communion. Then those who were going to fight rode or walked back to the ramparts.
From the great church the Emperor rode to the Palace at Blachernae. There he asked his household to forgive him. He bade the emotionally shattered men and women farewell, left his Palace and rode away, into the night, for a last inspection of the defence positions. Then he took his battle position.
The assault began after midnight, into the 29th of May 1453. Wave after wave the attackers charged. Battle cries, accompanied by the sound of drums, trumpets and fifes, filled the air. The bells of the city churches began ringing frantically. Orders, screams and the sound of trumpets shattered the night. First came the irregulars, an unreliable, multinational crowd of Christians and Moslems, who were attracted by the opportunity of enriching themselves by looting the great city, the last capital of the Roman Empire. They attacked throughout the line of fortifications and they were massacred by the tough professionals, who were fighting under the orders of Giustiniani. The battle lasted two hours and the irregulars withdrew in disorder, leaving behind an unknown number of dead and wounded.
Next came the Anatolian troops of Ishak Pasha. They tried to storm the stockades. They fought tenaciously, even desperately trying to break through the compact ranks of the defenders. The narrow area in which fighting went on helped the defenders. The could hack left and right with their maces and swords and shoot missiles onto the mass of attackers without having to aim. A group of attackers crashed through a gap and for a moment it seemed that they could enter the city. The were assaulted by the Emperor and his men and were soon slain. This second attack also failed.
But now came the Janissaries, disciplined, professional, ruthless warriors, superbly trained, ready to die for their master, the Sultan. They assaulted the now exhausted defenders, they were pushing their way over bodies of dead and dying Moslem and Christian soldiers. With tremendous effort the Greek and Italian fighters were hitting back and continued repulsing the enemy. Then a group of enemy soldiers unexpectedly entered the city from a small sally-port called Kerkoporta, on the wall of Blachernae, where this wall joined the triple wall. Fighting broke near the small gate with the defenders trying to eliminate the intruders.
It was almost day now, the first light, before sunrise, when a shot fired from a calverin hit Giustiniani. The shot pierced his breastplate and he fell on the ground. Shaken by his wound and physically exhausted, his fighting spirit collapsed. Despite the pleas of the Emperor, who was fighting nearby, not to leave his post, the Genoese commander ordered his men to take him out of the battle-field. A Gate in the inner wall was opened for the group of Genoese soldiers, who were carrying their wounded commander, to come into the city. The soldiers who were fighting near the area saw the Gate open, their comrades carrying their leader crossing into the city, and they though that the defence line had been broken. They all rushed through the Gate leaving the Emperor and the Greek fighters alone between the two walls. This sudden movement did not escape the attention of the Ottoman commanders. Frantic orders were issued to the troops to concentrate their attack on the weakened position. Thousands rushed to the area. The stockade was broken. The Greeks were now squeezed by crowds of Janissaries between the stockade and the wall. More Janissaries came in and many reached the inner wall.
Meanwhile more were pouring in through the Kerkoporta, where the defenders had not been able to eliminate the first intruders. Soon the first enemy flags were seen on the walls. The Emperor and his commanders were trying frantically to rally their troops and push back the enemy. It was too late. Waves of Janissaries, followed by other regular units of the Ottoman army, were crashing throught the open Gates, mixed with fleeing and slaughtered Christian soldiers. Then the Emperor, realizing that everything was lost, removed his Imperial insignia, and followed by his cousin Theophilus Palaeologus, the Castilian Don Francisco of Toledo, and John Dalmatus, all four holding their swords, charged into the sea of the enemy soldiers, hitting left and right in a final act of defiance. They were never seen again.
Now thousands of Ottoman soldiers were pouring into the city. One after the other the city Gates were opened. The Ottoman flags began appearing on the walls, on the towers, on the Palace at Blachernae. Civilians in panic were rushing to the churches. Others locked themselves in their homes, some continued fighting in the streets, crowds of Greeks and foreigners were rushing towards the port area. The allied ships were still there and began collecting refugees. The Cretan soldiers and sailors, manning three towers near the entrance of the Golden Horn, were still fighting and had no intention of surrendering. At the end, the Ottoman commanders had to agree to a truce and let them sail away, carrying their arms.
The Sultan, with his top commanders and his guard of Janissaries, entered the city in the afternoon of the first day of occupation. Constantinople was finally his and he intended to make it the capital of his mighty Empire. He toured the ruined city. He visited Saint Sophia which he ordered to be turned into a mosque. He also ordered an end to the killing. What he saw was desolation, destruction, death in the streets, ruins, desecrated churches. It was too much. It is said that, as he rode through the streets of the former capital of the Christian Roman Empire, the city of Constantine, moved to tears he murmured: "What a city we have given over to plunder and destruction".