During the Siege of Constantinople, the bulk of the Ottoman army were encamped south of the Golden Horn.
The regular European troops, stretched out along the entire length of the walls, were commanded by Karadja Pasha.
The regular troops from Anatolia under Ishak Pasha were stationed south of the Lycus down to the Sea of Marmara.
Mehmed himself erected his red-and-gold tent near the Mesoteichion, where the guns and the elite regiments, the Janissaries, were positioned.
The Bashi-bazouks were spread out behind the front lines.
Other troops under Zaganos were employed north of the Golden Horn.
Communication was maintained by a road that had been constructed over the marshy head of the Horn.
After the inconclusive frontal offensives, the Ottomans sought to break through the walls by constructing tunnels in an effort to mine them from mid-May to 25 May. Many of the sappers were miners of German origin sent from Novo Brdo by the Serbian Despot.
They were placed under the command of Zaganos Pasha.
However, the Byzantines employed an engineer named Johannes Grant (who was said to be German but was probably Scottish), who had counter-mines dug, allowing Byzantine troops to enter the mines and kill the Turkish workers.
The Byzantines intercepted the first Serbian tunnel on the night of 16 May. Subsequent tunneling efforts were interrupted on 21, 23, and 25 May, destroying them with Greek fire and vigorous combat.
On 23 May, the Byzantines captured and tortured two Turkish officers, who revealed the location of all the Turkish tunnels, which were then destroyed.
On 21 May, Mehmed sent an ambassador to Constantinople and offered to lift the siege if they gave him the city.
Constantine XI accepted to pay higher tributes to the sultan and recognized the status of all the conquered castles and lands in the hands of the Turks as Ottoman possession.
Around this time, Mehmed had a final council with his senior officers.
Here he encountered some resistance; one of his Viziers, the veteran Halil Pasha, who had always disapproved of Mehmed's plans to conquer the city, now admonished him to abandon the siege in the face of recent adversity.
Halil was overruled by Zaganos, who insisted on an immediate attack.
Having been accused of bribery, Halil Pasha was put to death later that year.
Mehmed planned to overpower the walls by sheer force, expecting that the weakened Byzantine defense by the prolonged siege would now be worn out before he ran out of troops and started preparations for a final all-out offensive.

After the Ottoman occupation of Constantinople, the Sultan ordered Zaganos to set out with his galleys for Galata, to prevent the Byzantine ships from setting sail.

The stories of Halil Pasha's collaboration with the Byzantines were most likely spread by the faction of Zaganos.
Zaganos succeeded Halil Pasha as Grand Vizier.
In 1456, however, Zaganos was made scapegoat after a failed expedition against Hungarian-held Belgrade.
Zaganos' daughter was expelled from the Sultan's harem, and the two were expelled to Balıkesir, where he probably had property.
In 1459, Zaganos returned and became kapudan pasha of the fast-growing Ottoman navy, and the next year he was the governor of Thessaly and Macedonia.
During the Siege of Constantinople, the bulk of the Ottoman army were encamped south of the Golden Horn. The regular European troops, stretched out along the entire length of the walls, were commanded by Karadja Pasha. The regular troops from Anatolia under Ishak Pasha were stationed south of the Lycus down to the Sea of Marmara. Mehmed himself erected his red-and-gold tent near the Mesoteichion, where the guns and the elite regiments, the Janissaries, were positioned. The Bashi-bazouks were spread out behind the front lines. Other troops under Zaganos were employed north of the Golden Horn. Communication was maintained by a road that had been constructed over the marshy head of the Horn. After the inconclusive frontal offensives, the Ottomans sought to break through the walls by constructing tunnels in an effort to mine them from mid-May to 25 May. Many of the sappers were miners of German origin sent from Novo Brdo by the Serbian Despot. They were placed under the command of Zaganos Pasha. However, the Byzantines employed an engineer named Johannes Grant (who was said to be German but was probably Scottish), who had counter-mines dug, allowing Byzantine troops to enter the mines and kill the Turkish workers. The Byzantines intercepted the first Serbian tunnel on the night of 16 May. Subsequent tunneling efforts were interrupted on 21, 23, and 25 May, destroying them with Greek fire and vigorous combat. On 23 May, the Byzantines captured and tortured two Turkish officers, who revealed the location of all the Turkish tunnels, which were then destroyed. On 21 May, Mehmed sent an ambassador to Constantinople and offered to lift the siege if they gave him the city. Constantine XI accepted to pay higher tributes to the sultan and recognized the status of all the conquered castles and lands in the hands of the Turks as Ottoman possession. Around this time, Mehmed had a final council with his senior officers. Here he encountered some resistance; one of his Viziers, the veteran Halil Pasha, who had always disapproved of Mehmed's plans to conquer the city, now admonished him to abandon the siege in the face of recent adversity. Halil was overruled by Zaganos, who insisted on an immediate attack. Having been accused of bribery, Halil Pasha was put to death later that year. Mehmed planned to overpower the walls by sheer force, expecting that the weakened Byzantine defense by the prolonged siege would now be worn out before he ran out of troops and started preparations for a final all-out offensive.
After the Ottoman occupation of Constantinople, the Sultan ordered Zaganos to set out with his galleys for Galata, to prevent the Byzantine ships from setting sail.
The stories of Halil Pasha's collaboration with the Byzantines were most likely spread by the faction of Zaganos. Zaganos succeeded Halil Pasha as Grand Vizier. In 1456, however, Zaganos was made scapegoat after a failed expedition against Hungarian-held Belgrade. Zaganos' daughter was expelled from the Sultan's harem, and the two were expelled to Balıkesir, where he probably had property. In 1459, Zaganos returned and became kapudan pasha of the fast-growing Ottoman navy, and the next year he was the governor of Thessaly and Macedonia.
Zagan Pasha