[1] He and Bishop Azelin of Hildesheim accompanied Henry on a 1051 campaign against King Andrew I of Hungary, whereby Benno distinguished himself in providing the forces' catering.
Stuck in the rising Saxon conflict, Henry IV strongly relyed on his abilities as a master builder of several castles in the mainland of Saxony, such as the Harzburg finished in 1068.
When the ambitious Cologne archbishop Anno II tried to bring him over to his side, the emperor designated him the successor of Bishop Benno I of Osnabrück who had died the past year.
Benno did a lot to promote the economic and agricultural development in his diocese, however, when in 1073 Henry's quarrels with the Saxon nobility culminated in open revolt, he had to seek protection at the royal court.
While Rudolf was killed in the Battle on the Elster, Benno and several bishops met in a synod at Brixen, where Gregory was again declared deposed and Archbishop Guibert of Ravenna was elected antipope.
On the other hand, Benno tried to bring about a reconciliation,[1] winning over rebellious nobles such as Margrave Egbert II of Meissen and even negotiating with the Roman Curia while the troops of Henry IV laid siege to the pope in the Castel Sant'Angelo.
From humble origins, Benno made a remarkable career, not only because his abilities were needed and appreciated, but also due to his social skills and his beneficial relations.