Feast of the Most Holy Name of Mary

The great victory, which John Sobieski, king of Poland, gained against the Turks under the walls of Vienna, caused the Pope Innocent XI to make this feast obligatory throughout the whole Western Church as a yearly act of thanksgiving for the deliverance of Christian Europe.

From the Catholic Encyclopedia Articles on Vienna and John Sobieski, detailing his glorious victory there over the muslim Turks:

"Vienna had to suffer another siege by the mortal foe of Christendom during the reign of Emperor Leopold I. Influenced by Louis XIV of France, the sultan sent directly against Vienna an army of 200,000 men under the command of the Grand Vizier Kara Mustapha; this army appeared before the city before the gathering of the imperial army had been completed... The Turks began the attack 13 July, 1683, and made violent assaults almost daily; the number of defenders sank from day to day, hunger and misery appeared, and the hospitals were full of sick and wounded. It was not until early in September that the relieving army, which had collected at Tulln, set out for Vienna; the commander-in-chief was the King of Poland, John Sobieski... The memorable battle began on 12 September; the Christian army descended form the Kahlenberg in three charges and won a brilliant victory over the Turks. Thenceforth Austria and Germany were permanently relieved of the danger of invasion by the Turks..."

"The Turks were routed, Vienna and Christendom saved, and the news sent to the pope and along with the Standard of the Prophet, taken by Sobieski, who himself had heard Mass in the morning. Prostrate with outstretched arms, he declared that it was God's cause he was fighting for, and ascribed the victory... to Him alone."

A conquerer like Caesar, yet unlike him a Christian, John Sobieski's words ring through the ages ascribing to God the ultimate victory of Christianity over Islam - Veni, vidi, Deus vicit (I came, I saw, God conquered).