Both Istanbul and Constantinople are used to refer to the same city, but Istanbul is the modern and official name of the city in Turkey. Constantinople was the city's name during the Byzantine Empire and for centuries afterwards. Today, Istanbul is the commonly accepted name for the city in everyday conversation and in official contexts. **

Constantinople's fall in 1453 to the Ottoman Empire is often seen as a symbolic end to the Middle Ages. The fall of the city marked the end of the Byzantine Empire, which had been a key player in the medieval world. The event also had significant repercussions on trade, culture, and politics in Europe, leading to the beginning of the Renaissance period. While it did not single-handedly end the Middle Ages, the fall of Constantinople was a significant event that contributed to the transition from the medieval to the early modern period. **

No, the Greeks do not call Istanbul Constantinople. The city was known as Constantinople during the Byzantine Empire, but after the Ottoman conquest in 1453, it was renamed Istanbul. Today, both Greeks and Turks refer to the city as Istanbul. **

The Crusaders attacked Constantinople in 1204 during the Fourth Crusade because they were diverted from their original mission to recapture Jerusalem and were instead persuaded by the Venetians to attack the Byzantine Empire. The Venetians had financial interests in the region and saw an opportunity to weaken their commercial rival, the Byzantines. Additionally, the Crusaders were promised financial and military support by the deposed Byzantine prince Alexios IV, who sought to reclaim the throne from his uncle. This combination of financial incentives and political maneuvering led the Crusaders to turn against Constantinople. **

The Ottomans conquered Constantinople in 1453 in order to expand their empire and establish control over the lucrative trade routes that passed through the city. Additionally, capturing Constantinople allowed the Ottomans to solidify their power in the region and establish themselves as a major world power. The conquest of Constantinople also marked the end of the Byzantine Empire and the beginning of the Ottoman Empire's dominance in the region. **

Expense refers to the money spent on goods or services, while payment refers to the actual act of transferring money to settle an expense. Revenue is the income generated from the sale of goods or services, while receipt is the physical evidence of receiving the revenue, such as a sales receipt or invoice. In summary, expense and payment are related to spending money, while revenue and receipt are related to earning money. **

The walls of the city of Constantinople were approximately 12 meters (40 feet) high and 5-6 meters (16-20 feet) thick. They were made of stone and brick, reinforced with towers and other defensive structures. These formidable walls played a crucial role in protecting the city from numerous sieges throughout its history. **

Fatih Sultan Mehmed Han managed to conquer Constantinople by employing a combination of military strategy, advanced weaponry, and determination. He utilized a massive army, including infantry, cavalry, and artillery, to besiege the city for nearly two months. Mehmed also ordered the construction of a massive cannon, known as the "Basilica," which was used to breach the city's walls. Additionally, he strategically positioned his troops and ships to cut off the city's supply routes and prevent reinforcements from arriving. Ultimately, Mehmed's relentless determination and innovative military tactics allowed him to capture Constantinople on May 29, 1453, marking the end of the Byzantine Empire and the beginning of the Ottoman Empire. **