The Diploma Ottonianum (also called the Pactum Ottonianum, Privilegium Ottonianum or simply Ottonianum) was an agreement between Pope John XII and Otto I, King of Germany and Italy. It confirmed the earlier Donation of Pepin, granting control of the Papal States to the Popes, regularizing Papal elections, and clarifying the relationship between the Popes and the Holy Roman Emperors. Description The forces of John XII, not yet 26 years of age, had been defeated in the war against Pandolfo Testa di Ferro of Capua, and at the same time many strongholds in the Papal States were occupied by Berengar of Ivrea, effectively if not completely legally King of Italy, and his son Adalbert. In this dilemma the Pope had recourse to Otto who reappeared in Italy at the head of a powerful army, as he had in the previous decade, now ostensibly as a papal champion. Berengar, however, did not risk an encounter, but retired to his fortified castles. Thus, without conclusive military encounters, on January 31, 962, Otto reached Rome. He took an oath to recognize John as Pope and ruler of Rome; to issue no decrees without the Pope's consent; and, in case he should deliver the command in Italy to anyone else, to exact from such person an oath to defend to the utmost of his ability the Pope and the Patrimony of Peter. The Pope for his part swore to keep faith with Otto and to conclude no alliance with Berengar and Adalbert. Subsequently, on February 2 Otto was solemnly crowned Holy Roman Emperor by the Pope. Ten days later at a Roman synod, John, at Otto's desire, founded the Archbishopric of Magdeburg and the Bishopric of Merseburg, bestowed the pallium on the Archbishop of Salzburg and Archbishop of Trier, and confirmed the appointment of Rather as Bishop of Verona. The next day, the emperor issued a decree, the famous Diploma Ottonianum, in which he confirmed the Roman Church in its possessions, particularly those granted by the Donation of Pepin and by Charlemagne, and provided at the same time that in future the Popes should be elected in canonical form, though their consecration was to take place only after the necessary pledges had been given to the emperor or his ambassadors. In essence, the Emperor was to be the guarantor of Papal independence, but to retain the right to confirm Papal elections. Historians debate, in terms