Why was constantinople difficult to invader and conquer А
The Byzantine Army was the first ones to use guns and cannons instead of swords and spears.
Constantine could see the enemy coming from miles away
Since the city was on trade routes between Europe and Asia, many Empires were friends instead of enemies with the Byzantines.
D
The Theodosian Walls protected the western border, while the Bosphorous River and Black Sea protected the north and south sides of the city