<P> Initially built by Constantine the Great , the walls surrounded the new city on all sides , protecting it against attack from both sea and land . As the city grew , the famous double line of the Theodosian Walls was built in the 5th century . Although the other sections of the walls were less elaborate , when well - manned , they were almost impregnable for any medieval besieger , saving the city , and the Byzantine Empire with it , during sieges from the Avar - Sasanian coalition , Arabs , Rus ' , and Bulgars , among others . The advent of gunpowder siege cannons rendered the fortifications vulnerable , but cannon technology was not sufficiently advanced to capture the city on its own , and the walls could be repaired between reloading . Ultimately the city fell from sheer weight of numbers of the Ottoman forces on 29 May 1453 after a six - week siege . </P>
<P> Initially built by Constantine the Great , the walls surrounded the new city on all sides , protecting it against attack from both sea and land . As the city grew , the famous double line of the Theodosian Walls was built in the 5th century . Although the other sections of the walls were less elaborate , when well - manned , they were almost impregnable for any medieval besieger , saving the city , and the Byzantine Empire with it , during sieges from the Avar - Sasanian coalition , Arabs , Rus ' , and Bulgars , among others . The advent of gunpowder siege cannons rendered the fortifications vulnerable , but cannon technology was not sufficiently advanced to capture the city on its own , and the walls could be repaired between reloading . Ultimately the city fell from sheer weight of numbers of the Ottoman forces on 29 May 1453 after a six - week siege . </P>
who constructed the massive defensive wall around constantinople in the early 5th century ce
who constructed the massive defensive wall around constantinople in the early 5th century ce
Constantine the Great
Constantine the Great