Excerpts from Books and Wikipedia
"Otto had been plagued by rebellions from rival duchies in his kingdom. . . . Yet further problems in southern Germany, and with Magyar raids, meant that it was not until 962 that Otto's position was secure enough for him to come to the aid of the Papal States at the request of Pope John XII. In return for Otto's guarantee of protection for the Papal States, the first such guarantee since the days of Charlemagne, Otto was crowned Holy Roman Emperor. He therefore became the first of a line that would last until abolished by Napoleon in 1806. Otto's first years as emperor were dogged by papal intrigue and rivalry. Despite this, his reign became known as the Ottonian Renaissance--many new cathedrals were built and a large number of illuminated manuscripts date from this time." [1001 Days]