Oh, here it is:
“It was on September 11 1683 that the conquering armies of Islam were met, held, and thrown back at the gates of Vienna.”
http://www.guardian.co.uk/world/2001/oct/03/september11.usa2
By now, everyday is probably some type of religious / battle / national anniversary. We’ll see if anyone claims this, and for what reason. Otherwise we’re just speculating.
If memory serves me, they were defeated by a force about 1/3
their size.