T. F. Tout, The Empire and the Papacy, 918-1273
“ Frederick did not shrink from the conflict. ‘No Roman Emperor,’ he declared, ‘has ever been so badly treated by a Pope. The Roman Church is so swollen with avarice that the goods of the Church will not suffice to satisfy it, and it is not ashamed to disinherit and make tributary emperors, kings and princes.’ For the moment Frederick was in the stronger position. The Pope’s emissaries failed to turn either Italy or Germany from its allegiance. The partisans of the Emperor stirred up a tumult in Rome, 368and at Easter 1228 Gregory was forced to take flight to Viterbo. ”
