The Red Apple, Kizil Elma.
Predicted by the Great Prophet Muhammad a millennium prior to today. There is a famous record in "Al-Sahifah al-Sadiqah" or "The Truthful Script" of Abd Allah ibn Amr ibn al-As asking The Great Prophet. He asked, "Which city shall be liberated first by us, is it Constantinople or Rome?"
He got an reply from The Great Prophet, it says. "The city of Heraclius will be liberated by us first." Taking in note that the Eastern Roman emperor in reign when he said this is Flavius Heraclius. The Great Prophet means Constantinople.
In a Hadith it recorded another saying, it says that "Constantinople shall be conquered, and whoever conquering her shall be the greatest general on the world, leading the best and most fearsome army that the world has ever seen." Mehmed is longing to take that title for him for so long, ever since his first ascension to the throne in the year 1444, he has been making plans to conquer this city.
Today is the day that he finally unleashes his plan.
Mehmed has waited too long for this, the Ottomans has waited too long for this, almost a hundred years since they first established their country in Prusa, Anatolia. They vowed they shall take it but failed multiple times.
Mehmed rode out of Edirne, reaching the Ottoman headquarters encampments of Çorlu the next day, where he was greeted by Karaca Pasha, the Bey of Rumelia whom Mehmed has previously appointed to build a chain of roads, bridges and high ways from Rumelia, Edirne, to Constantinople in order to ease the transport of supplies and ammunition. Looking from the smooth journey Mehmed got here, it seems like he did a pretty good job.
Karaca Pasha and some other commanders bowed towards the Sultan on horseback before he enters the camp. Mehmed nodded and gently placed his horse whip on Karaca Pasha's shoulders as a form of greeting back. Then he alighted the horse and walked into the Sultan's banner of white horse tent, while his Janissaries replaced all the guards outside the tent and stayed vigilant.
After everything is settled, Karaca Pasha, who was also in charge of assembling the army here, reported the current situation of the army. The standing army originally consists of Yaya and Musellem from all different Ottoman tributaries and eyelets in Anatolia, the notable consisting of forces from the emir of Cander and reinforcements from the emir of Karaman, some others consisting of soldiers from the various rump states in Armenia left by the Sultanate of Rum and the Ilkhante. They totally account for around ten thousand strong.
Then there's the Azabs, which are mostly lightly-armoured infantries, excel in close quarter combats, perfect scouts on horsebacks and can also be mounted archers who are used in hit and run tactics against those stubborn old Roman formations. They are recruited from every single Eyelet, city, town, village throughout the Sultanate, their order of assembly has been issued more than half a year ago. Fearsome warriors they are needless to say still with their lust for fight like their Seljik ancestors, but also a dangerous force which needs to be continuously satisfied with loots, women, gold and plunder. They account for around forty thousand strong in the army.
The bulk of Ottoman calvary force is formed by the Timarli Sipahi, like the Akinci, are light cavalry units that are not always assembled. They are mostly tribal riders and herds men in the Anatolian and Cicilian mountain ranges, continuing the life style like they are in the past nomadic steppe. Herding sheeps and horses. They train to ride horses, shoot arrows and wave Persian Shamshir blades since a very young age, they are the ones who outmatched the Roman elite calvaries by their speed and agility, they also went against the crusaders by the Franks, the Alermanians and the Bretons. They account for around twenty thousand in the ottoman army, making it perhaps the largest calvary force in Europe and Middle East.
There are also the private forces of all the landowners through out the Sultanate, raised as levies by the Sultan Mehmed II. Most of them responded and brought their own forces as levies, coming here on time. They are called the KapiKulu, or "Subject of the gate" following only the orders directly from the Sultan, no one else. They are a little bit like mercenaries lead by a knight in Europe. In order to appreciate their service, the Sultan would always generously allow them to share a portion of all loot and plunder. They account for around ten thousand forces in the army.
Finally, there are the Janissaries. Needless to say they are the most loyal force belonging, pad, and equipped directly by the Sultan. It is said that "Even if the sky came falling down, the Janissary will hold it for the Sultan". The Janissary mostly consists of heathen boys from conquered regions, converted and enslaved since a young age, taught under strict discipline and order. They will become the most elite troops surrounding the Sultan, serving the Sultan forever until forty years old, which is when they can be allowed to resume a supposedly normal life. There are around six thousand Janissaries priorly, but lost five hundred in the fortress of Rumelihisarı, thus there are only around five thousand and five hundred now.
This makes the Ottoman army size more than a hundred thousand men. Many might not have the concept of what a hundred thousand men means in a late medieval world. Taking in mind that the current population of Constantinople is merely fifty thousand, this means that the invading army that came for the city, is twice the number of the citizens. It is doubted that even if the Rex of the Franks, Charles VII De Valois Capet, the strongest monarch in Europe currently, cannot assemble a force of this size.
No matter how Mehmed looks from whatever perspective, he cannot think of any possible ways that he might lose the siege.