How a spiral staircase was a genius Castle defense

Have you ever wondered why most medieval castle stairs were built to be extremely narrow and spiral clockwise? Since medieval castles were built primarily as fortifications, the stairs were designed to make it impossible to launch a mass assault, as any attackers would have to ascend one at a time, with little space available for wielding weapons.

As most soldiers were right-handed, they would have to go around every curve of the inner wall before attempting to attack, inevitably exposing himself in the process. The clockwise spiral staircase also allowed the defenders to use the inner wall as a partial shield and allowed them to easily swing their weapon without being hindered by the curvature of the outer wall.

The stairs were also intentionally poorly lit and unevenly constructed, making it even more difficult for the attackers to gain any kind of balance or momentum during their fight to capture the castle.