The Battle of Viena was a big battlefield upset. Sobieski had only ~30,000 men when he defeated a Muslim Crusade force of ~300,000. It was such an embarrassing defeat for the Ottomans that they put their own leader, Mustafa, to death by strangulation. Had the Muslims sacked Vienna, they almost certainly would have marched on to take Rome, the Vatican and the Catholic Church, which would have been the end of Western Civilization. In this light, it was arguably as significant as the Battle of Thermopylae (but hasnt had a blue screen movie made about it yet (and may never given the sensitivities)).
Lawrence Wright wrote in The Looming Tower (Pulitzer winner) about Sept. 11, 1683 --
"For the next three hundred years, Islam would be overshadowed by the growth of Western Christian societies...."
Osama bin Laden picked the date for the WTC attacks and saw it as Islam’s big comeback. The date has since been used by other jihadis, including the attack on the US compound in Benghazi which killed Ambassador Stevens and 3 other Americans.