To put the matter briefly, the military leaders developed into barons and princes, and in some cases the nominal centralisation culminated as in France and England in the kingly office; while, in Germany and Italy, it took the form of the revived imperial office, the spiritual over-lord of the whole of Christendom being the Pope, who had his vassals in the prince-prelates and subordinate ecclesiastical holders. In addition to the princes sprung originally from the military leaders of the migratory nations, there were their free followers, who developed ultimately into the knighthood or inferior nobility; the inhabitants of the conquered districts forming a distinct class of inferior freemen or of serfs. But the essentially personal relation with which the whole process started soon degenerated into one based on property. The most primitive form of property--land--was at the outset what was termed _allodial_, at least among the conquering race, from every social group having the possession, under the trusteeship of its head man, of the land on which it settled. Now, owing to the necessities of the time, owing to the need of protection, to violence and to religious motives, it passed into the hands of the over-lord, temporal or spiritual, as his possession; and the inhabitants, even in the case of populations which had not been actually conquered, became his vassals, villeins, or serfs, as the case might be. The process by means of which this was accomplished was more or less gradual; indeed, the entire extinction of communal rights, whereby the notion of private ownership is fully realised, was not universally effected even in the west of Europe till within a measurable distance of our own time.[6]