Otto I, his son Otto II, and his grandson Otto III were successively acknowledged emperors and kings of Italy, from 961 to 1002. When this branch of the house of Saxony became extinct, Henry II of Bavaria and Conrad the Salian of Franconia filled the throne from 1004 to 1039. During this period of nearly eighty years, the German emperors twelve times entered Italy at the head of their armies, which they always drew up in the plains of Roncaglia near Piacenza: there they held the states of Lombardy, received homage from their Italian feudatories, caused the rents due to be paid, and promulgated laws for the government of Italy. A foreign sovereign, however, almost always absent, known only by his incursions at the head of a barbarous army, could not efficaciously govern a country which he hardly knew, and where his yoke was detested. During these five reigns, the social power became more and more weak in Italy. The emperors were too happy to acknowledge the local authorities, whatever they were, whenever they could obtain from them their pecuniary dues: sometimes they were dukes or marquises, whose dignities had survived the disasters of various invasions and of civil wars; sometimes the archbishops and bishops of great cities, whom Charlemagne and his successors had frequently invested with duchies and counties escheated to the crown, reckoning that lords elected for life would remain more dependent than hereditary lords; sometimes, finally, they were the magistrates themselves, who, although elected by the people, received from the monarch the title of imperial vicars, and took part with the nobles and prelates in the _plaids_ (_placita_), or diets of Roncaglia. In the time of Conrad the Salian, the prelates almost throughout Lombardy joined the cities against the nobles; and from 1035 to 1039 there was a general war between these two orders of society. Conrad put an end to it, by a constitution which is considered to be the basis of feudal law. By this the inheritance of fiefs was protected from the caprices of the lords and of the crown,--the most oppressive conditions of feudal dependence were suppressed or softened,--and the few remaining slaves of the land were set free. THE EMPIRE AND THE PAPACY