About 919 Otto's father King Henry the Fowler had a "Kaiserpfalz" erected in Merseburg in the Eastphalian "Hassegau", hometown of his first wife Hatheburg of Merseburg. The establishment of the diocese traced back to a vow Otto took before his victory against the Hungarians at the Battle of Lechfeld on Saint Laurence day, 10 August 955. Confirmed by Pope John XIII at the 968 synod in Ravenna, the first Merseburg bishop was Boso, a Bavarian monk descending from St. Emmeram's Abbey in Regensburg (Ratisbon), already distinguished by his missionary labours among the pagan Sorbs.