He was originally a counsellor of Frederick II and was entrusted with the education of Frederick's son Manfred. He was at Manfred's side until his defeat at the Battle of Benevento in 1266. In that year he went to Viterbo, Italy and arranged the marriage of his daughter to the Neapolitan Guelph, Bartholomew Caracciolo, and then served with the Hohenstaufen army. After the defeat of the Hohenstaufens at Tagliacozzo he escaped to Venice. His estates were confiscated by Charles; and his wife and daughter were mistreated or raped by the French knight sent to evict them and one of his sons murdered. In 1269 or 1270 he was in Germany trying to drum up support for the return of the Hohenstaufen to the throne of Sicily. While existing Sicilian legends overplay John of Procida's role in the dramatic politics of this time, Runciman concurs that he was at the centre of a "vast political conspiracy" in support of the House of Hohenstaufen (backed by the Byzantines and their Genoese allies) and against Charles of Anjou and his ally the Pope.