In the broadest sense, it was a way of structuring society around the relationships that resulted from the possession of land in exchange for services or labor. The serfs formed the lowest class in feudal society. In many medieval countries, a villein could gain freedom by fleeing a mansion to a city or district and living there for more than a year, but this action involved the loss of land rights and agricultural livelihoods, an unaffordable price unless the landowner was particularly tyrannical or conditions in the village were exceptionally harsh. Too many models of feudalism used for comparisons, even by Marxists, are still either built on the basis of the 16th century or include what in a Marxist view must certainly be superficial or irrelevant features of it. Even limiting themselves to Europe and feudalism in the narrow sense, it is highly doubtful whether feudal institutions formed a coherent set of institutions or concepts structurally separate from the other institutions and concepts of the time. [48] Many empires have established vassal states based on tribes, kingdoms, or city-states whose subjects they want to control without having to conquer or rule them directly. .