In art a style can never be imposed nor predicted. It grows organically from any given epoch reflecting the needs, wants and desires of that epoch. Great art always reflects a timeless universal truth that moves through every epoch. Another way to say that is that every epoch has it’s own stories and story tellers. To truly understand the events and people in any point in history you most know their stories and story tellers.
The problem with many historians today is that they do not know the stories of the time they are reporting on or worse, they apply our stories to that time and that leads to a gross misrepresentation of that time. Otherwise know as revisionist history.
In Belloc’s book, The Crusades, he takes extra care to remind us of the story and the story tellers of that time. He points out the successes and failures of that first crusade in light of how the participants of that time viewed the world and themselves. The book reads like a detective story as told in flash back because he tells us the end in the first few pages.
The reason, of course, that this account of the Crusades is not used in schools is that the story of the time is Christianity and the cause of the Crusades was to save Christendom. Also Belloc, rightly so, connects he and us to that story and frequently uses phases like, “We failed…” or “Our fathers…”. Also he does not paint the Mohammedan forces as noble nomads just looking for a homeland as in Ridley Scott’s Kingdom of Heaven but as what they really were at that time a barbaric culture bent on destruction incapable of building and creating anything.
The other reason is that he predicts that since we lost the main goal of the crusades, “we have by no means seen the last of the results of the 12th-century Christian military failure against Islam.”
Much better review of the book is here