In A.D. 960 Pope John XII called in Otto the Saxon from beyond the Alps, as Stephen II had called in Pepin the Frank; [footnote] and in A.D. 962 Otto was crowned Emperor in Rome by John, as Charles had been crowned in 800 by Leo.
Otto’s passage of the Alps in A.D. 961, in response to the call of Pope John XII, was not, of course, his first appearance in Italy, any more than Pepin’s passage of the Alps in A.D. 755, in response to the call of Pope Stephen II, was the first occasion on which the Franks had shown themselves on Italian ground. As early as A.D. 951 Otto had already visited Italy on his own initiative in order to establish his suzerainty over the North Italian “successor-state” of the Carolingian Empire. This was ten years before he himself assumed the Italian Crown at Pavia in A.D. 961, and eleven years before he was crowned Emperor at Rome in 962.
A Study of History, Vol IV, OUP, 1939