I always thought it was the gates of Vienna.
Sobieski defeated 300-350,000 Turks with some 70,000 men at the battle of Vienna.
in 732 A.D. no army lay between Islam and western Europe except 1 that of Charles Martel.
Islam had already conquered an empire larger than the Roman Empire using their army on horseback: One man Martel saved Europe , Christianity and civilization:
http://www.citizenwarrior.com/2009/10/on-this-day-in-732-charles-hammer-saved.html
https://www.frontpagemag.com/fpm/242777/remembering-battle-tours-mark-tapson
Islam conquered most of the Middle East and North Africa and then came across the Straights of Gibraltar and conquered Spain, subjugating the people under Islamic rule, giving the European (mostly Christian and Jewish) people the choice of conversion to Islam or perpetual underling status burdened with a tax on non-Muslims (vital funds Muslims used to finance further conquests).
Islamic armies moved north into what is now France (known as Gaul at the time). That was the high-water mark of Islam’s first major invasion of Europe, because it was there they were stopped.
After several large battles, the Islamic hordes were defeated by an army led by Charles Martel, who came to be known as Charles the Hammer. The final and decisive battle occurred on October 11th, 732, one hundred years after the death of Mohammad....
http://www.citizenwarrior.com/2009/10/on-this-day-in-732-charles-hammer-saved.html
I wonder why government schools never teach this? Democrats are the enemy