It states "practice of grinding the bones of fallen soldiers into munitions ". I think that we can rule out the possibility that the Japanese managed to convert human bone to either nitrocellulose or some similar nitrate explosive, and if the Japanese were still using black powder in their artillery ( they'd dropped it for their small arms) it's similarly hard to imagine deriving potassium nitrate, sulfur and charcoal from the same source...and when you consider the amount of propellant required for a large naval gun, it's even harder to imagine . If someone at the munitions plant was putting a pinch or two of bone ash into a shell, however, that would not have been hard; there would be room for it, along with the propellant..