Our series on understanding Islamic State attempts to catalogue many of the forces and events that can arguably have played a part in creating the conditions necessary for these jihadists to emerge.
Representing even the Crusades as wars between Christians and Muslims is a gross oversimplification and a misreading of history.
In seeking to link IS to earlier Islamic movements, Western commentators have associated the jihadist group with the medieval Ismailis, made famous in Europe by returning Crusaders as the Assassins.
Despite what we're told, religion isn't inherently peaceful. People kill in the name of their religion, just as they love in its name.