Exactly, them and their herds and their caravans. They'd have to go through routes of (comparatively) easy water-access, which was monopolized by the state. Much how like rulers built toll-roads and toll-bridges.



They weren't school textbooks, they were thick, smooth-papered, hard-covered, no-worksheeted stuff. Now I remember that a couple of them were DK's (about Biology or Plants or such), but the most memorable ones were published by someone else.