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.
Historians debate, in terms of power and prestige, whether the Diploma Ottonianum was a prestigious advantage for the papacy or a political triumph for the emperor.
The Pope now quickly changed his mind, while Otto on his part pressed his imperial authority to excessive limits, and the brief alliance dissolved in wrangling.
The recognition of the Church's property and rights which found expression there would surely have been advanced by the Curia in case of emergency on the ground of earlier confirmations without this gesture of Henry's...' (Mikoletzky, Heinrich II.