Yep. I read that one last year, and it turned out to be excellent. Belloc did indeed paint Islam as a terrible heresy of Christianity – which it is – and made the case that secular modernity, brought on by Christianity's own successes in civilising Mankind, is now the greatest threat that the Faith faces.

Yes, Emmet Scott talks quite a bit about how Christianity freed and saved thousands of Irish slaves in the Dark and Middle Ages, and how Irish monks then went forth to spread the Word to other shores. His book, Mohammed and Charlemagne Revisited: The History of a Controversy, is really very good.

The " Heresy of Muhammed" being one of the largest and most persistent of the attacks on the Church, all over the world.

Today, I think the West is in the midst of a pincer attack, with the latest resurgence of Islam on the one side and what Belloc called "the modern attack" on the other.

Marxism and its seemingly infinite types and derivatives are forms of that "modern" attack.

How the Irish Saved Civilization: The Untold Story of Ireland's Heroic Role From the Fall of Rome to the Rise of Medieval Europe , by Thomas Cahill.

It is an excellent historical study concerning how western civilization was preserved during the middle ages by Irish monks–from the destructive forces of the Vikings, as well as Islam. It is well worth the read.

Dire Badger is quite right. Mercy is often stupid. As the scriptures say,
"There is a way that seems right to a man, but in the end leads only unto death."

Our biggest mistake in history was in not detroying islam at it's source when we finally had the upper hand… They would have done it to us. Heck, that's pretty much what China managed to do to the mongols, albeit in a weird passive-aggressive way.
Mercy is often stupid.