Jihad Watch commemorates the fall of Constantinople to the Turks; the day one of the bastions of Christianity fell to the Muslims. Since I could not find a permalink to the particular article, I have copied it into the extended section below.

Black Tuesday on a Monday
On Tuesday, May 29, 1453, the armies of the Ottoman Sultan Mehmet II entered Constantinople, breaking through the defenses of a vastly outnumbered and indomitably courageous Byzantine force. Historian Steven Runciman notes what happened next: the Muslim soldiers "slew everyone that they met in the streets, men, women, and children without discrimination. The blood ran in rivers down the steep streets from the heights of Petra toward the Golden Horn. But soon the lust for slaughter was assuaged. The soldiers realized that captives and precious objects would bring them greater profit." (The Fall of Constantinople 1453, Cambridge University Press, 1965, p. 145.)

It has come to be known as Black Tuesday, the Last Day of the World.

Some jihadists "made for the small but splendid churches by the walls, Saint George by the Charisian Gate, Saint John in Petra, and the lovely church of the monastery of the Holy Saviour in Chora, to strip them of their stores of plate and their vestments and everything else that could be torn from them. In the Chora they left the mosaics and frescoes, but they destroyed the icon of the Mother of God, the Hodigitria, the holiest picture in all Byzantium, painted, so men said, by Saint Luke himself. It had been taken there from its own church beside the Palace at the beginning of the siege, that its beneficient presence might be at hand to inspire the defenders on the walls. It was taken from its setting and hacked into four pieces." (P. 146.)

The jihadists also entered the Hagia Sophia, which for nearly a thousand years had been the grandest church in Christendom. The faithful had gathered within its hallowed walls to pray during the city’s last agony. The Muslims, according to Runciman, halted the celebration of Orthros (morning prayer); the priests, according to legend, took the sacred vessels and disappeared into the cathedral’s eastern wall, through which they shall return to complete the divine service one day. Muslim men then killed the elderly and weak and led the rest off into slavery.

Once the Muslims had thoroughly subdued Constantinople, they set out to Islamize it. According to the Muslim chronicler Hoca Sa’deddin, tutor of the sixteenth-century Sultans Murad III and Mehmed III, "churches which were within the city were emptied of their vile idols and cleansed from the filthy and idolatrous impurities and by the defacement of their images and the erection of Islamic prayer niches and pulpits many monasteries and chapels became the envy of the gardens of Paradise."

Tuesday has been regarded as unlucky by superstitious Greeks ever since.

Why did this happen?

It had been a long time coming. The once-great Empire had been by the time of this last siege of Constantinople reduced to little more than the city itself. But a few chief causes can be isolated:

1. Realpolitik. Short-sighted Byzantine Emperors such as John VI Cantacuzenes made ill-advised alliances with the Ottomans; in 1347 he invited them into Europe to aid them in a dynastic dispute, and they haven't left yet.

2. Disunity. The Western European powers were themselves disunited and preoccupied with their own affairs. Compounding that was the fact that they couldn't rally much support for a bailout of the Byzantines without an ecclesiastical unity that, when it was affected on paper by the Patriarch of Constantinople and the Emperor, was rejected by the people of the Empire. The force the West finally sent was too small, and it was annihilated by the Muslims at Varna in Bulgaria in 1444. Far too many Westerners didn't see the peril of Constantinople as their peril, and far too many Easterners subscribed to the Byzantine official Lukas Notaras' quip: "Better the turban of the Sultan than the tiara of the Pope."

Yes, well, Notaras found out otherwise when the Sultan took a liking to the official's teenage boys ("like pearls," Qur'an 52:24) and had them beheaded before his eyes when Notaras refused to give his blessing to the Sultan's taking them for his pleasure. The Pope, for all his enormities, was not likely to have done that.

Meanwhile, the world has forgotten what happened on Black Tuesday, and so many other days like it from India to Spain, and persists in the fantasy that Islam does not contain an imperialist impulse and that Muslims can be admitted without limit into Western countries without any attempt to determine how many would like ultimately to subjugate and Islamize their new countries, the way their forefathers did to Constantinople so long ago.

And today we see the same ill-informed games of realpolitik, pragmatic alliances made with those who would conquer and subjugate us, and the same disunity and finger-pointing at each other instead of unity in the face of this threat to our common survival. It is the same sentiment Pastor Niemöller bewailed in his famous poem -- may we be spared from discovering when they come for us that there is no one left to speak for us, for they have all already been taken.

I know that may be too much to ask. After all, you are a _____. What possible accord could you have with ______s? Fill in the blanks yourself. And remember when you do, that both groups you filled the blanks in with are on the list of those the mujahedin wish to subjugate.

It is fitting that Black Tuesday coincides this year with Memorial Day. For only a strong defense -- not just military, but cultural and spiritual, a civilizational defense -- will conquer the forces of jihad and keep there from being many more Black Tuesdays, many more Last Days of the World. May we mount that defense, and speedily.