Preparation for the conquest of Istanbul started only one year ahead. Huge cannons that were necessary for the siege were moulded. In 1452, Rumeli Castle was constructed to control the Bosphorus. A mighty fleet of 16 galleries was formed. The number of the soldiers were doubled. The supply routes to Byzantine were taken under control. An agreement was made with Genoese to keep Galata impartial during the war. In April 1453, the first Ottoman frontier forces were seen in front of Istanbul. The siege was starting.
|6 April 1453
||Sultan Mehmed pitched his imperial tent by the door of St. Romanus in Topkapi. The same day the city was besieged from the Golden horn to the Marmara Sea from the land.
|6-7 April 1453
||First cannons were fired. Some of the fortresses in Edirnekapi were destroyed.
|9 April 1453
||Baltaoðlu Suleyman Bey launched the first attack to enter the Golden Horn gulf.
|9-10 April 1453
||Some of the fortresses on bosphorus were taken. Baltaoðlu Suleyman Bey seized the Marmara Islands.
|11 April 1453
||The big fortress were bombarded by cannon fires. Holes and cracks were opened here and there. Serious destruction inflicted by ceaseless bombardment.
|12 April 1453
||The Ottoman fleet attacked the ships protecting the Golden Horn. The victory of the Christian ships decreased the morale of the Ottoman army.At the order of Sultan Mehmed, the Byzantine ships were pounded by mortar fire, and one galley was sunk.
|18 April 1453
||At night, the Sultan gave his first crucial order. The attack lasted 4 hours but it was scattered.
|20 April 1453
||A naval skirmish took place close to Yenikapi between the Ottoman fleet and 4 Byzantine warships with three supply ships full of food and weapons sent by the Papacy. the Sultan came to the shore himself and ordered Baltaoðlu Suleyman Pasha to sink those ships by any means possible. The Ottoman fleet could not stop enemy’s ships which were bigger. With this failure the Ottoman army lost its morale and showed the signs of defeat. Ottoman soldiers started defecting from the army. Soon, the Byzantine Emperor wanted to take advantage of this situation and offered peace.
The offer, supported by famous Vizier Candarli Halil Pasha, was rejected by Sultan Mehmed. The siege and bombardment of the fortresses with cannons continued.
During this chaos and widespread feeling of defeat, a letter from the Sultan’s spiritual teacher Akshemseddin promised good news about the conquest. Encouraged by this spiritual support, Sultan Mehmed escalated the attack and decided to add an element of surprise: the Ottoman fleet anchored in Dolmabahce would be moved to the Golden Horn gulf by land.
|22 April 1453
||In early hours of the morning, Byzantine Christians were dumbfounded and horrified when they saw Ottoman galleys moving down on the hills of the bay. Seventy ships carried by cows and balanced by hundreds of soldiers via ropes were slid over slipways. by afternoon the ships were inside the well protected bay.
The surprise appearance of the Ottoman fleet in the bay created panic among Byzantine residents on Constantinople. The fortresses on the shore of Golden Horn became a vulnerable spot and some of the Byzantine forces were moved there. This weakened the defence of the land fortresses.
|28 April 1453
||The attempt to burn the Ottoman ships in the bay was prevented by heavy cannon fire. A bridge was constructed between Ayvansaray and Sutluce to attack the fortresses located on the shore of the bay.
An offer of unconditional surrender was delivered to the Emperor through the Genoese. If he surrendered he could have gone wherever he wanted and the life and property of his people would have been spared. the Emperor rejected this offer.
|7 May 1453
||A three hour long attack was launched on the stream of Bayrampasa with a 30,000 strong force, but it was failed.
|12 May 1453
||A thunderous attack made towards the point between Tekfursaray and Edirnekapi was defeated
|16 May 1453
||When the underground tunnel dug in the direction of Eðrikapi intersected by Byzantinian underground tunnel, an underground skirmish erupted.
The same day, an attempt to cut the sturdy chain blocking the entrance of the bay failed. The following day the attack was repeated, but again ended with failure.
|18 May 1453
||Ottoman forces launched another attack from the direction of Topkapi, by using a wooden mobile tower. The Byzantine burned the tower at night and emptied the trenches that were filled by Ottomans.
|25 May 1453
||Sultan Mehmed, sent Isfendiyar Beyoðlu Ismail Bey as an ambassador offering Emperor to surrender for the last time. Accordingto this offer, the Emperor and his followers could take their wealth and go anywhere they wish. The people who decided to stay could keep their belongings and estates. This offer was too rejected.
|26 May 1453
||According to rumors European countries and especially Hungarians were planning to mobilise their troops to help the Byzantines unless the siege was ended. Upon hearing these rumors, Sultan Mehmed gathered his war council. In the meeting Candarli Halil Pasha and his party defended their previous position, that is, of putting an end to the siege. Sultan Mehmed with his tutor Zaðanos Pasha, his teachers Akshemseddin, Molla gurani and Molla Husrev opposed the idea of quitting.
They decided to continue the was and Zaðanos Pasha was commissioned for preparations.
|27 May 1453
||The general attack was announced to the Ottoman army.
|28 May 1453
||The army, spent the day by resting and preparing for the next day’s attack. There was a complete silence among the soldiers. Sultan Mehmed inspected the army and encouraged them for the great attack.
On the other side, a religious ceremony was held in Hagia Sophia Church. the Emperor urged people to participate in the defence. This would be the last Byzantine ceremony.
|29 May 1453
||Platoons positioned for the assault. Sultan Mehmed gave the order to attack at midnight. Inside Constantinople, while the soldiers positioned for war, people filled the churches.
The Ottoman army launched its final assault accompanied by commemoration of God and beats of drums. The first assault was performed by the infantry and it was followed by Anatolian soldiers. When 300 Anatolian soldiers were martyred, the Yeniceri (Janissaries) started their attack. With the precence of Sultan Mehmed, the Ottoman army was motivated and chest to chest fights started. Meanwhile the young soldier called Ulubatli Hasan who first erected the Ottoman flag on Byzantine land fortresses was martyred. Upon the entrance of the Yeniceri from Belgradkapi front, the Byzantine defence collapsed.
Abandoned by his soldiers, the Emperor was killed during street skirmishes.
Turkish forces entered from every direction and crushed the Byzantine defence completely. Towards noon Sultan Mehmed entered the city, he had a new name then : Sultan Mehmed the Conqueror. He went directly to Hagia Sophia Church and converted it to mosque.