There is a ton of misinformation about how the Union of Florence played out in Constantinople in the lead up to the fall of the city. The worst ones are that Emperor Constantine XI Paeologous died a unionist and that there was some kind of joint liturgy where everyone forgot their differences and happily accepted the union and commemorated the Pope. I find that the primary sources do not bare this out.
Doukas
The Greek historian Doukas who spent his life working for the Italian rulers of Lesbos and was a pro-unionist but specifically says the Emperor was an insincere unionists. In this extract he is talking about a union liturgy held by Cardinal Isidore on the 12th of November 1452. "2. After the emperor had received them with the courtesy and honor befitting their station, they came to the topic of Union. The emperor and several representatives of the Church assented to the Union. However, the greater portion of the sacerdotal and monastic orders, abbots, archimandrites, nuns-why do I say the greater portion? It was the nuns who urged me to speak and to write. Not one among them assented to the Union. Even the emperor only pretended to do so. Nonetheless, they who appeared to be in favor of the Union came to the Great Church." Doukas (trans. Harry Magoulias), Decline and Fall of Byzantium to the Ottoman Turks, Section XXXVI.2. Wayne State University, 1975, page 204.
This is what Doukas says about the church service held on the arrival of Cardinal Isidore (a Greek Unionist) with a boatload of mercenaries paid for by the Pope. "5. When the Christians who had assembled in the Great
Church had offered an extended prayer to God and had listened to the cardinal's words, they agreed to the Article of Union with the understanding that, once the Turkish threat had passed and peace was restored, a number of scholars would gather to study the articles and correct whatever was not in complete accordance with the true faith. With this understanding, therefore, they consented to hold a combined liturgy in the Great Church to be celebrated by both Italians and Greeks. After both Pope Nicholas and the exiled Patriarch Gregory were commemorated in the diptychs, the Divine Liturgy was concluded on the twelfth day of December in the year 6961. There were many who did not receive the offering of antidoron because it represented an abominable sacrifice celebrated in the Unionist Liturgy. Every heart and every intent of the Greeks was examined, and their trickeries and deceptions did not escape the cardinal's detection. Since he belonged to the same nation, he needed little prompting to offer the City his help. He was content, therefore, to report to the pope only what had taken place. The rest he entrusted to God Who administers all things for the good." Doukas (trans. Harry Magoulias), Decline and Fall of Byzantium to the Ottoman Turks, Section XXXVI.5. Wayne State University, 1975, page 205. Notice how Doukas doesn't even bother talking about how many got communion from Isidore as he says many didn't even accept the innocuous antidoron. And these were the Greeks who were supposed to be supporters of the union.
This bit has Doukas venting against the anti-unionists population of Constantinople "6. But the populace, cruel and hating the good, the root of arrogance, the branch of vainglory, the flower of haughtiness, the dregs of the Hellenic nation, wholly disdaining the nations of men, regarded all the events that had taken place as though they had not occurred at all. In conversation the Unionists would say to the schismatics, "Let us see if God will remove this enemy who opposes us, the great dragon who boasts that he will swallow the City whole, and then you will see if we will unite with the Azymites." In saying these things, the wretches did not know that the many oaths sworn in the name of the Holy Trinity on pain of indissoluble excommunication to up- hold the union and concord of Christians, that is, of the Churches, which had been sanctioned at the Council of Lyons in the days of the first Palaiologos [Michael VIII, 1274 A.D.] and in the Council of Florence in the days of the last Palaiologan Emperor [John VIII, 1439 A.D.), and now in this Divine and Sacred Liturgy, would remove their commemoration from the earth, and with them, the commemoration of the City. O wretches, why do you reflect upon such vanities in your hearts? Behold your priests and your nuns and your monks, your male and female sacristans! They refused to communicate the Immaculate Body and Blood from the hands of those Greek priests who administer the Blessed Sacraments according to the ecclesiastical tradition of the East, contending that they are polluted and that "they are not Christian sacraments." Moreover, they avoided the blessing of those priests and called the churches pagan altars. Tomorrow they will be corrupted and defiled in both body and soul. I saw with my own eyes a nun who had taken sacred vows not only eating meat and covering her body with barbarian dress but also making an offering to the false prophet and shamelessly confessing his unholy faith. But what has made me jump ahead five months in time? Tomorrow these things will be upon us and they will be recounted with lamentations. Doukas (trans. Harry Magoulias), Decline and Fall of Byzantium to the Ottoman Turks, Section XXXVI.6. Wayne State University, 1975, page 205-6.
In another section Doukas explains how anti-unionists shunned the Eucharist from the Church of Hagia Sophia due to its unionist clergy and simply left the church before communion. "9. From that day on which the Union had supposedly taken place in the Great Church, the Constantinopolitans shunned it as though it were a synagogue of Jews, and neither oblation nor burnt offering nor censing took place inside. If one of the priests offered the Divine Liturgy to God on a feast day, the worshipers would remain to the time of the oblation and then they would all depart, women as well as men and monks as well as nuns. What need be said? They looked upon the church as a pagan altar and the sacrifice as offered to Apollo. For this reason, Isaiah, as from the mouth of God, says, "Behold, I will proceed to remove this people and I will remove them: and I will destroy the wisdom of the wise, and will hide the understanding of the prudent. Woe to them that deepen their counsel, and not by the Lord. Woe to them that take secret counsel, and whose works are in darkness, and they say, Who has seen us? And who shall know us or what we do?" Therefore, saith the Lord, "Woe to the apostate children! Ye have framed counselnot by me, and covenants not by my Spirit, to add sins to sins.'" Doukas (trans. Harry Magoulias), Decline and Fall of Byzantium to the Ottoman Turks, Section XXXVlI.9. Wayne State University, 1975, page 209.
In this extract Doukas mocks the Constantinoplians for hiding in Hagia Sophia as the Turks poured into the city after previously shunning the church. "18. Why were they all seeking refuge in the Great Church? Many years before they had heard from some false prophets that the City was fated to be surrendered to the Turks who would enter with great force, and that the Romans would be cut down by them as far as the Column of Constantine the Great. Afterwards, however, an angel, descending and holding a sword, would deliver the empire and the sword to an unknown man, extremely plain and poor, standing at the Column. "Take
this sword," the angel would say, "and avenge the people of the Lord." Then the Turks would take flight and the Romans would follow hard upon them, cutting them down. They would drive them from the City and from the West, and from the East as far as the borders of Persia, to a place called Monodendrion. Because they fully expected these prophecies to be realized, some ran and advised others to run also. This was the conviction
of the Romans who long ago had contemplated what their present action would be, contending, "If we leave the Column of the Cross behind us, we will avoid future wrath." This was the cause then of the flight into the Great Church. In one hour's time that enormous temple was filled with men and women.There was a throng too many to count, above and below, in the courtyards and everywhere. They bolted the doors and waited, hoping to be rescued by the anonymous savior. 19. 0 miserable Romans! 0 wretches! The temple which only yesterday you called a cave and altar of heretics, and not one of you would enter so as not to be defiled because the liturgy was offered by clerics who had embraced Church Union, and now, because of the impending wrath you push your way inside, seeking to be saved. But not even the impending just wrath could move your hearts to peace. And even if, in such a calamity, an angel were to descend from heaven and say to you, "If you will accept the Union and a state of peace in the Church, I will expel the enemy from the City," even then you would not assent. And if you did assent, it would only be a lie! They who but a few days before had said, "It would be better to fall into the hands of the Turks than into the clutches of the Franks," knew this was true." Doukas (trans. Harry Magoulias), Decline and Fall of Byzantium to the Ottoman Turks, Section XXXIX.18-19. Wayne State University, 1975, page 225-6.
This evidence doesn't sound like the huggy and kissy version of events that often circulate around the internet. The anti-unionist participation in joint religious services seems very conditional and limited. There is no hint of widespread acceptance of communion from the populace of Constantinople from unionists or even the antiodoron (if you know what that is). Please note that this is coming from a pro-unionist and this is his best spin.
Leonard of Chios
Leonard of Chios was Latin bishop of Chios and a typical anti-Orthodox bigot. He went to Constantinople with Cardinal Isidore and survived. He later wrote a letter to Pope Nicholas on the fall of the city.
On arriving in Constantinople Leonard of Chios makes it clear that amost nobody supported the union. I find it striking that he doesn't include Emperor Constantine Paeologous as a supporter of the union. "I soon realised that except for the learned Argyropulus, Theophilus Palaeologus and a few monks and lay theologians, almost all the Greeks were seized by an excessive partiality; and that there was none who could be moved by zeal for the Faith or for his own salvation to be the first to express contempt for their obstinate opinions..., it was arranged by the industry and probity of the aforementioned Cardinal that the Holy Union should be confirmed, with the agreement (if it was not feigned) of the Emperor and his Senate, and celebrated on the second day before the Ides of December, the holy day of the Bishop Spiridion." English translation from J.R. Melville Jones, The Siege of Constantinople, 1453: Seven Contemporary Accounts (Amsterdam, 1972), p. 12-13.
"The Greeks celebrated the Union in words, but denied it in fact. Some of their leaders, whose blood now waters the earth, spilt by enemy swords, said, 'Let the High Pontiff be given the honour of being commemorated in the service, but let the decree of the Synod of Florence be not read.' Why this, hypocrite ? 'In order,' they replied, 'that the section of the decree which claims that the Holy Spirit proceeds from the Son as well as the Father may be blotted out.' Again why, hypocrite ? 'So that the Greeks may not appear to be in error, if it is said that the Holy Spirit proceeds from two sources.' Why again,
pray, hypocrite ? 'To prevent the glory from accruing to the one who desires to win it all, by virtue of his office.' Scholarius on the one hand, and Notaras on the other, intended at some time to present themselves before the Apostolic Presence, claiming that they alone had understood the matter, and should be praised as the leading figures in making the Union; for many were secretly tortured with jealousy of the Papal legate [= Cardinal Isidore]." English translation from J.R. Melville Jones, The Siege of Constantinople, 1453: Seven Contemporary Accounts (Amsterdam, 1972), p. 19.
This is what Leonard of Chios says about the Turks massacring the Byzantines sheltering in Hagia Sophia. "Their soldiers ran eagerly through it, putting to the sword all who resisted, slaughtering the aged and the feeble-minded, the lepers and the infirm, while they spared those of the rest who surrendered to them. The heathen infidels entered Sancta Sophia, the wonderful
shrine of the Holy Wisdom, which not even the temple of Solomon could equal, and showed no respect for the sacred altars or holy images, but destroyed them, and gouged the eyes from the saints. They broke and scattered their holy relics too, and then their sacrilegious hands reached out for the sacred vessels of God, and they stuffed their pouches with gold and silver taken from the holy images and from the sacred vessels. Screams and cries rose to the heavens, and sseveryone of both sexes, and all the precious metal and property of all kinds in the city, were subject to their pillage. With axes they broke open our store-chests, and dug in the earth in their search for valuables, which they found, both new and old, in such abundance, that no city in this age could show the like for wealth. All that had been hidden away now passed into their hands." English translation from J.R. Melville Jones, The Siege of Constantinople, 1453: Seven Contemporary Accounts (Amsterdam, 1972), p. 38.
George Sphrantzes
Sphrantzes was a loyal friend and courtier of Emperor Constantine. He as present throughout the siege and survived. He wrote a short chronicle in his old age. He says "My late emperor, the martyr, lived forty-nine years, three months and twenty days. His reign lasted four years, four months and twenty-four days. He had been the eighth emperor of the Palaeologian Dynasty. " XXXV.10. Marios Philippides (Translator)The Fall of the Byzantine Empire: A Chronicle by George Sphrantzes, 1401–1477, University of Massachusetts Press, 1980. Page 70.
"The emperor consented to have the Pope's name commorated in our services, by necessity, as we hoped to receive some aid... Six months later we had received as much aid from Rome as had been sent to us by the Sultan of Cairo." XXXVI.6. Marios Philippides (Translator)The Fall of the Byzantine Empire: A Chronicle by George Sphrantzes, 1401–1477, University of Massachusetts Press, 1980. Page 72.
Sphrantzes was a staunch anti-unionist yet he considers Constantine Palaeologus a martyrs. This confirms Constantine Paeologous's lack of real support for the union. If anyone knew it would have been Sphrantzes. The Greek Orthodox tradition is universal in considering Constantine Paeologous an Orthodox martyr. The fact that his Megadux was the notoriously anti-unionists Lucas Notaras and that George Scholarius maintained a correspondence with him also confirms Sphrantzes view.
Rather than rejoicing at the Union of Florence, Roman Catholics should be embarrassed that they imposed impossible conditions on the desperate Byzantines.