Fall of Constantinople

One of the first major uses of cannon artillery was the Ottoman siege of Constantinople; Orban, a Hungarian, initially tried to sell his "Basilica" cannon design services to the Byzantines, who were unable to secure the funds needed to hire him. Later, he built the cannon for Turkish siege forces; thusly, one of the longest enduring empires came to an end.

The Fall of Constantinople was the capture of the capital of the Eastern Roman (Byzantine) Empire by an invading army of the Ottoman Empire on Tuesday, 29 May 1453. 

After the conquest, Sultan Mehmed transferred the capital of the Ottoman Empire from Edirne to Constantinople. Several Greek and other intellectuals fled the city before and after the siege, with the majority of them migrating particularly to Italy, which helped fuel the Renaissance.

The capture of Constantinople marked the end of the Roman Empire, an imperial state which had lasted for nearly 1,500 years.