 Complete the following phrase:  According to the historian Doukas, on the morning of 29 May 1453, the small postern called Kerkoporta was left open by accident, allowing the first fifty or so Ottoman troops to enter the city. The Ottomans raised their banner atop the Inner Wall and opened fire on the Greek defenders of the peribolos below. This spread panic, beginning the rout of the defenders and leading to the 