The cannon

When the Ottoman army reached the walls of Constantinople in April 1453, it was hauling along a large number of artillery pieces, the use of which was to prove decisive in taking the city. It had become clear that medieval fortifications, with their high but relatively weak walls, no longer presented a serious challenge to cannon. The new fortification system established in the 16^th century to counter this threat had two main features:

• Shorter, thicker walls, inclined on the outer side to withstand cannon fire.
  
• Bastions, i.e. polygonal or semi-circular ramparts projecting from the curtain walls, serving as artillery emplacements for the defenders.