P. V. N. Myers, A General History for Colleges and High Schools…
“ Each vassal became a virtual sovereign in his own domain. And when these great vassals divided their fiefs and granted them to others, they in turn invested their vassals with those powers of sovereignty with which they themselves had been clothed. Thus every holder of a fief became " monarch of all he surveyed." To illustrate the workings of the system, we will suppose the king or suzerain to be in need of an army. He calls upon his own immediate vassals for aid; these in turn call upon their vassals; and so the order runs down through the various ranks of retainers. ”
