As we have seen, the chief beneficiaries of the weakness of the later Carolingian emperors were the magnates — the great landowners who converted the public duty to defend imperial interests into personal rights over territory and, ultimately, arrogated to themselves the hereditary title to the great offices of imperial state. For some three hundred years from the middle of the 9th century — the high age of feudalism — their sovereign ambitions were limited by the stagnation of the fragmented economy and the degradation of the means of transport, which the very circumstances of their emergence entailed. They were, of course, also limited by the strength of their neighbours and there was a two-way struggle between them and traditional or putative centralizing powers on the one hand, residual county or radical communal authorities on the other.