Well, it sure seems as though Dale is right on this one, the Emporer Constantine Palaiologos did in fact die somewhere near the "Gate of Saint Romanus" .
His body was never recovered. He was the last man to call himself "Emporer of the Romans".
The Gate was called Topkapi by the Ottomans. At least the museum of the same name existed until the 1960's-I assume it is still there, but i am not going to make the same assumptions about the gate as I have no present knowledge as to its condition.
The Byzantine Empire had been steadily shrinking since the Battle of Manzikert, a disastrous loss by the Empire to the Seljuk Turks. It was a battle they could have won.
At the time of the 1st Crusade, which seems to have been largely Norman French Driven, many of the Crusaders considered the Byzantine Imperial Army to be the best in the World.
The Imperial Army took advantage of the Crusade and its victory over the Seljuks at Dorylaeum and the fall City of Antioch to the "Latin Crusaders" and occupied much of it the territory lost after Manikert.
I do not recall that the Orthodox Empire felt comfortable to follow the Crusaders further than that City.
As you well know the Byzantine Empire had been steadily shrinking before the Arab Expansion and then the Seljuk and Ottoman Conquests since the 8th Century.
So my error will cost you all some heavy reading (or not) as well as the opptunity to enlighten me further.
In any case, the Emporer in 1453 had only 50-75,000 subjects, 99% within the walls of Constantinople, and his realm consisted of what is shown within the City walls.
The above picture does not show "Pera" on the other side of the Golden Horn.
The "walls" of the City.
Trained military personnel of the Garrison included about 5,000-6000 Greeks (not known if from the City) and 2000-2500 foreigners, probably mostly Genoese and some Venetian mercenaries or volunteers..
So, even though up to 30,000 civilians aided in the defense of the city, although partly just serving as laborers repairing the breaches made by Mehmet's guns; a fairer phrase to have been used would have been, at best, the Byzantines "could" not serve in their own defence.
One source does say (if I can find it again) what the defenders lacked in sophistication, they compensated for in enthusiasm.
It is suprising to note that even in what is now modern day Turkey, the Ottomans did not hold pervasive sway, and, apparenty, had to contend with Timur I Leng (Tamerlane-he hated being called that as it named him as 'lame") and the areas of influence of the Seljuks and other Turkish 'groups".
Many things developed or used by the Ottimans (heavy siege artillery, fife and drums corps to name two) were copied and adopted by the West.
The elite "shock troops" of Mehmet's Army were the Janissaries, children mostly born of Christian or other non Islamic peoples, raised in Islam and the Military life (re-envisioned by Frank Herbert is the "Sarduakar" in the Science Fiction novel of the 60's: "Dune". Although Herbert stayed pretty well away from religious shadings.)
The walls alone did not prevent the sacking of the City, as Hugh noted, by the Western Fourth Crusade. However IF I recall correctly, the Crusaders may have had already been allowed within the City when, ah, shall we saying stealing and looting on site seemed better than contuing to the Holy Land.
However, this is in question as some sources as the tension and hatred extant between the Latin Papacy and The Greek Orthodox Patriarchy at that time is no secret.
to be continued----