 Walter III of Brienne died in June 1205 while fighting in southern Italy . His widow Elvira of Sicily gave birth to a posthumous son , Walter IV , who grew up in Italy . John assumed the title of count of Brienne , and began <unk> the county on his nephew 's behalf in 1205 or 1206 . As a leading vassal of the count of Champagne , John frequented the court of Blanche of <unk> ( who ruled Champagne during her son 's minority ) . According to a version of Ernoul 's chronicle , she loved John " more than any man in the world " ; this annoyed Philip II of France . 
