The key to understand the Templar's philosophy is to realise how the Order was founded solely as an instrument for the noble families in Burgundy.

Chapter 9 in "900 Years" describe how these families consider themselves as "sons of Zadok" - and it describes how the whole idea of "crusades" in reality was invented as a conspiracy between these relatives and a prominent member of the families: Pope Urban II.

Nothing is as it seems to be, and thus the real background for the crusading army was political - not religious.