The history of Istanbul is very closely related to its geographical situation. It has been determined that there are some residential areas in the city dating back to prehistoric times. During the excavations carried out on Fikir Hill around Kadıköy between 1942 and 1952, B.C. Some tools and skeletons dating back to 3,000 years ago have been found. This situation clearly reveals that people lived on the Asian shores of Istanbul in those times. If excavations are carried out on the Rumelia side, it is thought that various ruins from ancient times will be found there as well. The first inhabitants of the core of today's Istanbul cities, that is, the part south of the Golden Horn, were Thracians. The Phoenicians settled in Kadıköy. As it is known, Thracians are Indo-European and Phoenicians are Semitic races. According to the Greeks; A group of Greeks under the rule of Byzas in Megara, Greece, B.C. They came to today's Srayburnu and settled in 658. In the following centuries, the city gradually became a secondary port and trade city. This trade city, which preserved its internal independence under Roman rule, only survived in A.D. II. It became a Roman site in the century. Emperor Constantine started the construction of a new and large city in 325. On May 11, 330, this city became the capital of the world empire, replacing Rome. Already during the reign of Constantine, the population of the city exceeded 200,000. But it was far from reaching the population and size of Rome, which had a population of several million. When the empire was divided into two in 395, Istanbul became the capital of the Eastern Empire. During the reign of Justinian, that is, VI. In the century, its population exceeded one million and it became the largest city in the world. VII. Although Baghdad surpassed Istanbul in terms of population, size and wealth starting from the end of the century, the city never lost its population exceeding a million. However, this large population was dispersed during the occupation of the Latins. Atilla, the ruler of the Hun Turks, who came to Europe after the collapse of their empire in Asia and was in the largest part of this continent, came to Büyükçekmece in 447; but he returned after tying Byzantium to an annual tax. After the Huns, the Avar (Apar) Turks, who lost their imperial throne in Asia, came to Europe and advanced as far as Istanbul in 616. The Avars' siege of the city in 626 created one of the most important threats faced by Byzantium throughout history. Iranians (Sassanids) were also participating in this siege from Kadıköy and Üsküdar. By great luck, Byzantium survived this siege under harsh conditions. After the emergence of Islam, one of the main targets of the Arabs was Istanbul. The siege of 668-669 was held under the commander-in-chief of the future caliph Yazid. The Islamic navy, which destroyed the Byzantine navy in 665, had prepared an open door for this siege. The Prophet's standard bearer Khalid Ibn Zayd (Abu Ayyubu'l-Ansari) and many of the Prophet's friends participated in this expedition. When this siege yielded no results, Caliph Muawiyah had the city besieged by land once again in 673-674. The Arabs based themselves on the Kapıdağı peninsula and appeared in front of Istanbul during the campaign season for seven years. However, no result was achieved due to the "Greek Fire", whose composition was known only to the Byzantines. In 713-714, Prince Mesleme besieged Istanbul again. This siege brought Byzantium to the danger of collapse. It was considered a matter of days before the Arabs took the city and dominated Europe. But Emperor Leon's energy saved the situation. This siege is considered one of the turning points in European history. In 781, the future caliph Harunureshid besieged the city; but was withdrawn in exchange for an annual tax. From now on, Bulgarian Turks posed the greatest threat to Istanbul. In 813, Kurum Khan, after destroying the Byzantine army in the Edirne pitched battle, besieged the city. But the majesty and durability of its multi-layered walls saved Byzantium again. In 1090, another Turkish community, the Pechenegs, came to Çekmece. A few years after Manzikert, the Seljuk Turks came to Üsküdar and made Iznik the capital of Turkey; but they could not pass to Europe. The First Crusade saved Byzantium from the Seljuk Turks. And it pushed back the conquest of Byzantium by the Turks by 3.5 years. On April 16, 1204, the fourth Crusade, which was prepared with the aim of saving Byzantium from the hands of the Turks, turned specifically towards Byzantium. Poor Europeans, dazzled by the majesty and wealth of the city, captured Istanbul after a fierce war. For the first time in history, barbarians dominated the city. The city of millions faced the most terrible looting, murder and attacks and lost most of its wealth. Tens of thousands of manuscripts were burned. Churches were looted down to their last candlesticks. Tens of thousands of Istanbulites were put to the sword. Women were attacked. Not only warriors but also Latin Priests participated in all these movements. Taking refuge in Iznik, the Byzantine Empire embarked on a relentless struggle to take its capital from the Latins. The Latins established an empire in Istanbul and gave the throne to a French Dynasty. Finally, in 1261, the Byzantines under the rule of the Palaiologos expelled the Latins from Istanbul. The capital of the empire was transferred from Iznik to Istanbul again. However, during this period, the city's population had fallen below half a million, according to estimates. However, it was the largest city in Europe - excluding the Arab cities in Spain. Until this period, the population of no city in Christian Europe exceeded 150,000. After this, Byzantium faced the Ottoman Turks. Later, Orhan Bey came to Üsküdar. He established very close relations with the Emperor. In the spring of 1390, Yıldırım Bayezit, the grandson of Orhan Gazi, besieged the city, but lifted the siege in return for a heavy tax. Yıldırım's determination and decision to take Istanbul was final. However, the Timur incident put this conquest behind by half a century. The lightning that destroyed the great Crusader army consisting of the forces of all European states that came to expel the Turks from Europe and save Byzantium in 1396, had the Anatolian Fortress built and besieged the city in 1397. But he did not engage in siege warfare; He did not want to tie large Turkish troops to the city. He thought that with a long blockade, Istanbul, like Bursa, would bow and surrender. While Byzantium was in this situation, Timur defeated Yıldırım in 1402. Yıldırım's son Musa Çelebi besieged Istanbul in 1411, but could not take it. Yıldırım's grandson II. Murat's siege, which was the scene of very fierce battles that lasted from 15 June to 24 August 1422, showed that the city was living its last days. An uprising in Anatolia saved Byzantium this time. But II. Murat's son II. Mehmet almost made taking the city a fixed idea. He captured Istanbul on May 29, 1453, ending the Middle Ages.