Let us invoke the holy name of Mary when faced with grave dangers

The next day, September 12th, Sobieski entered the city triumphantly, and attended Mass and the Te Deum (a solemn song of thanksgiving) in the church of the Virgin of Loreto to whom he attributed the victory.

Pope Innocent XI also attributed this victory to the intercession of the Virgin. In thanksgiving, he decided to institute a feast in honor of the Holy Name of Mary.

On November 25, 1683, the feast was extended to the whole Church, and the Nativity of Mary was fixed for the following Sunday. It was Pope Saint Pius X who then decided to set the date to September 12th, not on the anniversary of the victory itself, but on the anniversary of its celebration. When Saint John Paul II restored this feast, it was to remind Catholics to invoke Mary when facing serious international dangers too.

Rome, September 11, 2015 (ZENIT.org)