On this day we celebrate the feast of the Most Holy Name of Mary.
For an explanation of the feast, see The Liturgical Year, the great classic by the Right Reverend Dom Prosper Guéranger, Abbot of Solesmes, pages 171-195. From that:
"Two glorious triumphs, two victories won under the protection of our Lady, have rendered this present day illustrious in the annals of the Church and of history.
"Manicheism, revived under a variety of names, had established itself in the South of France, whence it hoped to spread its reign of shameless excess. But Dominic appeared with Mary's Rosary for the defence of the people. On the 12th of September 1213, Simon de Montfort and the Crusaders of the faith, one against forty, crushed the Albigensian army at Muret. This was in the pontificate of Innocent III.
"Nearly five centuries later, the Turks, who had more than once caused the West to tremble, again poured down upon Christendom. Vienna, worn out and dismantled, abandoned by its emperor, was surrounded by 300,000 infidels. But another great Pope, Innocent XI., again confided to Mary the defence of the baptized nations. Sobieski, mounting his charger on the feast of our Lady's Assumption, hastened from Poland by forced marches. On the Sunday within the Octave of the Nativity, 12th September 1683, Vienna was delivered; and then began for the Osmanlis that series of defeats which ended in the Treaties of Carlowitz and Passarowitz, and the dismemberment of the Ottoman empire. The feast of the most holy Name of Mary inscribed on the Calendar of the universal Church, was the homage of the world's gratitude to Mary, our Lady and Queen." Page 193.
Wikipedia's article on Sobieski's victory at the Battle of Vienna is excellent. From that:
"In honor of Sobieski, the Austrians erected a church atop a hill of Kahlenberg, north of Vienna. The train route from Vienna to Warsaw is also named in Sobieski's honour. The constellation Scutum Sobieski (Sobieski’s Shield) was named to memorialize the battle. Because Sobieski had entrusted his kingdom to the protection of the Blessed Virgin (Our Lady of Czestochowa) before the battle, Pope Innocent XI commemorated his victory by extending the feast of the Holy Name of Mary, which until then had been celebrated solely in Spain and the Kingdom of Naples, to the universal Church; it is celebrated on 12 September."
("Culinary Legends" contains speculation about the origin of the croissant.)
Click here for The Siege of Vienna: The Last Great Trial Between Cross & Crescent, by John Stove, Pegasus, 2008.
Click here for The Enemy at the Gate: Habsburgs, Ottomans, and the Battle for Europe, by Andrew Wheatcroft, Basic Books, 2008. Search terms: Virgin Mary, grenades.
Blessed be the name of Mary, Virgin and Mother.