In Worcester Cathedral Library, we have a 1555 edition of Roberto Valturio’s De Re Militari (On the Military Arts) printed in France in French and Latin. The book was probably written about a hundred years earlier – Valturio died in 1475, and by the time our edition was published certain aspects of it must have been wildly out of date. Mechanical siege engines, for instance, must have been entirely replaced with gunpowder weapons by the mid-16th Century.
However, people were still clearly interested enough in Valurio’s work in this period for it to have been still in print. Perhaps this was due to the quality and clarity of the draughtsmanship evident in the illustrations, with clean lines and a clear sense of perspective. Indeed, it has been suggested that this work was a key influence on Leonardo Da Vinci, particularly that aspect of his work which focused on military engineering.
A Cathedral library might not be the first place you would go to find a military textbook. That we have many more than just this one (although none quite so attractive) is evidence of the great breadth of bibliographic material that the clergy at Worcester collected over the years.
 http://www.metmuseum.org/toah/works-of-art/26.71.4 [accessed 05/09/2014].