For the developments of the Middle Ages See Serfdom and Villenage.
The great beauty and fertility of the country, as well as the charm of its climate, undoubtedly attracted, even in early ages, successive swarms of invaders from the north, who sometimes drove out the previous occupants of the most favored districts, at others reduced them to a state of serfdom, or settled down in the midst of them, until the two races gradually coalesced.
Moreover, many proprietors contrived to curtail seriously the allotments which the peasants had possessed under serfdom, and frequently they deprived them of precisely the parts which they were most in need of, namely, pasture lands around their houses, and forests.
The lay subjects of the Order consisted of two classes; on the one hand there were the conquered Prussians, in a position of serfdom, bound in time of war to serve with the brethren in foreign expeditions; on the other hand there were the German immigrants, both urban and rural, along with the free Prussians who had voluntarily submitted and remained faithful.
The influence of the Northern invasions on the change from slavery to serfdom was, in all probability, of little account.