Actually, it came to a head the first time at the Battle of Tours in France in (I believe) 732, when the Franks under Charles Martel defeated the Moors who were advancing northward from Spain...
It's "come to a head" many, many time since then, one of the most memorable being the fall of Constantinople to the Turks in 1453. A lot of the mess in the Balkans today (Bosnia, Sarajevo, Serbia, Macedonia, Muslims vs. Serbs vs. Croats, etc.) can be directly traced back to that.
So you see, it isn't as simple as it at first appears on the surface--but then, things rarely are.
Nothing is more frightening than ignorance in action.
