overlordship. Henry's other asset lay in the comparatively recent rise of his family, the Liudolfings: he had succeeded his father, Otto, as Duke of Saxony in 912. The law of consanguinity was not yet fully defined, and churchmen were as yet hesitant in invoking it, but it was already the case that marriage could for several generations prevent the marriage of descendants; in time the number of generations was defined as seven, but this was not strictly enforced. A new dynasty thus had the advantage of an old one, for it still had a reasonably free choice of the politically most advantageous marriages before it. The asset was naturally a wasting one, but it helped Henry draw Lotharingia back into the kingdom under his brother-in-law, Duke Giselbert, and was to be a major element in the success of his son and successor, Otto I ( 936-73).
Upon Henry's foundations Otto was able to raise the German monarchy to one of its greatest peaks. In this he was aided by a happy combination of circumstances. To the east he unleashed a series of campaigns against the pagan Slavs between the Elbe and the Oder, who were also being menaced from the nascent duchy of Poland under Mieszko I; that helped to provide territory and manpower with which he might bind men to him. To the west he was favoured by the intermittent conflicts between the Carolingians and Robertians which made it unappealing for the dukes of Lotharingia to throw off his rule for they could expect little help from France if they did so. Within Germany marriages of his relatives into the ducal families secured their accession to Swabia and Bavaria, while Lotharingia was bestowed on a son-in-law. To the south the turbulent politics of Italy provided a fruitful sphere in which to intervene, bringing Otto the crown of Italy in 951, the imperial crown in 962, and a rich harvest of relics with which he could endow the great eastern bishoprics and monasteries. By appointing bishops to sees well distant from their native parts he helped to create alternative sources of support should their neighbours prove restive and was at the same time able to impose military obligations on the Church to defend the eastern frontier and provide troops for more distant expe-
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