On May 29, 1453, Sultan Mehmed II defeated Emperor Constantine XI Palaiologos to capture Constantinople, by ingenious strategy, and overwhelming army, and an innovative use of gunpowder to nullify Constantinople's extraordinary fortifications. Emperor Constantine's dwindling army was aided by a few hundred men from the Papal States and Genoa, as well as a handful of ships from Venice that were already in Constantinople, which, except for a further fleet sent from Venice that failed to arrive in time, was the most that the West would volunteer at that period of increasing hostility between East and West. It was, for all that, a closer thing than is sometimes admitted; attempts to treat the fall of Constantinople as inevitable tend to overlook both how extraordinary Constantinople's fortifications were, and also how much in the way of military talent and resources the Sultan had to bring to bear in order to accomplish it. The Ottoman army had heavy losses; their victory was hard-won. In the confusion, nobody knows for sure what happened to the Emperor.
And so fell, once and for all, the Roman Empire. Thousands of Christians were killed in the aftermath, and thousands sold into slavery. The Ottomans looted the city for three days -- Mehmed II could not deny them the right because it was part of their pay. But it is said at the end of it that he wept, saying, "And see what a city we have submitted to plunder and destruction."
Cappella Romana and Alexander Lingas perform Guillaume Du Fay's Lamentatio Sanctae Matris Ecclesiae Constantinopolitanae:
Du Fay (or Dufay) was a Flemish composer who made his way to Italy in the fifteenth century; his most famous work is probably the motet, Nuper rosarum flores, which was written for the consecration of the Cathedral in Florence, but this one, reflecting on the loss of Hagia Sophia, is in some ways more haunting. It is in content a lament of the Holy Virgin seeing her Son crucified, which also represents the lament of the Church.