The idea began to germinate watching students read Tres Fabulae Horrificae. They were enamored with the pictures even, if in the case of my 7th grade class, the text was too advanced for them to read. I decided to write another illustrated book.
Then a series of circumstances fell into place. I own an English mastiff. His name is Sherman and he is a veritable rock star everywhere he goes. Luckily, he is also both gentle and gregarious so being surrounded by admirers is just fine with him. His physique is more "traditional" than some of his breed. He is lankier with a longer snout and shaggier fur than some of the modern "show" mastiffs. He of course is not a Molossus but there is a resemblance to the ancestral dog.
Secondly, I came in contact with Andy Volpe, a Roman re-enactor who does presentations for schools about Roman armor and weapons among other things. He did a demo for my class which they greatly enjoyed. He is also a part of Legio III Cyrenaica which also puts on demos for the public. Thirdly, I have known a group of Celtic re-enactors for many years. They also participate in demos and events with the SCA. Suppose a legionary had a Molossus? Suppose this Molossus was gentle like Sherman rather than fierce? Would there be a place in the army for such a dog? Thus the story was created. I started with live actors, added a large dose of photoshop, and sprinkled in some stock photos Finally, everything was strained through artistic filters and Ecce! the book was created.