Any work of fiction weaves around real things. Authors use real cities, nations, historical figures, and events as a setting for the fictional story. Think of the real things as a stage on which the fiction plays out.
I think readers might like to know the real history of the setting in which I have placed The Templar Concordat. While the book takes place in modern times, it reaches back to the Crusades to set its stage. So, I have provided a brief description of major elements of the Knights Templars, Church, Hashashin, and the Crusades. There is also a short description of the weapons used by the major characters.