Mohammed fully realized that the siege of Constantinople would be a formidable task even for his army of 80,000 men. The weakest side of the triangle was the Golden Horn. Here the shore was dotted with wharves and warehouses - ideal sites for landing parties. Here the crusaders had forced entry, and so could Mohammed once he gained control of the harbor. That task was assigned to Suleiman Baltoghlu, the governor of Gallipoli. This Bulgarian-born renegade was given command of the largest Turkish fleet ever assembled - several hundred craft. But Baltoghlu was designed to end his days in poverty and disgrace.

The single wall that faced the Golden Horn curved around the southern, tip of the city and continued along the snore of the Sea of Marmora. The point of the city was virtually unapproachable by ships because of swift currents. The Marmora side, except for two small fortified ports, was protected by shoals and rocks. Thus, until Baltoghlu could breech the boom and seize the Golden Horn, the main weight of the Turkish attack had to be thrown against the powerful treble walls facing the land.

The first obstacle facing Mohammed's troops was a moat sixty feet wide and a minimum twenty-five feet deep. At one point the depth actually reached a hundred feet. Many sections of the moat could be flooded from cisterns in the city. On the inner edge of the moat was a low crenelated wall. Behind this was a broad roadway. Then rose the Outer Wall, twenty-five feet high and ten feet thick, studded with towers every fifty to a hundred yards. Behind these fortifications was another roadway. Then began the great Inner Wall, forty feet high and fifteen feet thick, buttressed with huge towers that soared sixty feet.

For most of their length - nearly four miles these walls sat on high ridges, but from the Civil Gate of St. Romanus and the Gate of Charisius the land dropped sharply a hundred feet into the Lycus Valley where Mohammed had established his headquarters and deployed the Janissaries. This low-lying section of the walls was called the Mesoteichion and was considered the weakest point. There was one other vulnerable area - at the Golden Horn end of the walls where a single wall enclosed the suburb of Blachernal. These were the points where Mohammed concentrated his main bombardments.

The Emperor Constantine took personal command of the Greek troops defending the Mesoteichion opposite Mohammed and his Janissaries. He was well qualified to assume this duty. Although he had been emperor for only a few years, he was a swarthy, robust man in his early fifties who had proven himself earlier in Greece to be a competent administrator and a sound military commander. On the second night of the siege he closely supervised the rebuilding of the section of the wall near the Gate of Charisius which the Turkish cannon had destroyed that day. By morning the repairs were adequate.

Constantine had decided to make his stand on the Outer Wall. On the Emperor's right was Giustiniani with his Genoese troops. He faced the Turkish European divisions. On the emperor's left were companies of Greeks, Genoese and Venetians opposing Turkish troops from Asia Minor. The Marmora wall was lightly defended by Catalans, a small band of Turks under Prince Orhan, a pretender to the Ottoman throne, and some Greek monks. Venetian and Genoese sailors were assigned to the Golden Horn. Camped behind the Turkish lines were the Bashi-bazouks as a reserve. Across the Golden Horn was the small Genoese suburb of Pera containing the walled town of Galata. This settlement of prosperous merchants maintained an uneasy neutrality throughout the siege. During the fighting they traded with both sides, and Pera was a hotbed of Turkish and Greek spies. While one hand permitted the Greeks to affix one end of their boom to Pera's walls, the other hand was negotiating with Mohammed for favorable trade concessions in the event of Constantinople's fall. The Sultan had guaranteed Pera's neutrality, but he did not trust these Christians and deployed a large portion of his army in the hills behind the town.