By September 1683 the Ottoman army of Kara Mustafa Pasha — perhaps 150,000 strong — had besieged Vienna for two months. The Holy Roman Empire's defenders were exhausted, the walls breached, the city facing the prospect of being the next Constantinople. Pope Innocent XI called the universal Church to public Rosary processions and to fasting and almsgiving.
On September 11–12 a relieving Christian army of some 70,000 — German, Imperial, Polish — under the command of King Jan III Sobieski of Poland reached the heights of the Kahlenberg above Vienna. At dawn on September 12 Sobieski heard Mass and is reported to have said: 'Let us begin with the Mass and end with the Rosary.' That afternoon he led the entire Polish 'winged' Hussar cavalry — some 18,000 horse — down the hill in what remains the largest cavalry charge in military history.
The Ottoman army broke in less than three hours. Sobieski sent the captured banner of the Prophet to the Pope with a paraphrase of Caesar: 'Veni, vidi, Deus vicit' — 'I came, I saw, God conquered.' Pope Innocent XI extended the feast of the Holy Name of Mary, originally a Spanish observance, to the universal Church and fixed it permanently to September 12 in memorial of the victory.