Until 9/11, most people had never heard the word "jihad."
But Robert Spencer had, and soon, people all over the world were turning to his website JihadWatch.com to learn more about America's "new" enemy.
But as Spencer (a Christian who is fluent in Arabic and can quote the Koran chapter and verse) can explain, Islam has been at war with the West since its founding 1400 years ago.
Spencer is so eloquent when it comes to debunking myths, such as the alleged "reasons" for today's Islamic terrorism. (It has nothing to do with the birth of the state of Israel or U.S. foreign policy, but everything to do, he says, with the teachings of Mohammad.)
We talk about little known historical incidents, like the Muslim slave raids on Ireland, and the role Islam has played in slavery for centuries, up to the present day.
All this and much more is laid out in his new book, the title of which says it all: The History of Jihad: From Muhammad to ISIS.