In 1355, following the Ottoman capture of Gallipoli in the previous year, Paul entered into negotiations with the Byzantine emperor, John V Palaiologos, for a rapprochement between Byzantium and the Catholic Church, in exchange for Western military aid. Paul secured considerable concessions from the hard-pressed emperor, including the active promotion of the Latin Church and even the Latin language, the dispatch of his son Manuel as a hostage to the papal court, and the establishment of a permanent papal legation in Constantinople. During his stay in Constantinople, Paul also took part in a theological disputation between Gregory Palamas and Nikephoros Gregoras. In early 1356, Paul, accompanied by the Byzantine ambassador, the "megas hetaireiarches" Nicholas Sideros, set sail for the papal court at Avignon, where they arrived in early June. Pope Innocent VI answered to the emperor's offers with generalities, and avoided to commit himself to the dispatch of military aid, but sent Peter Thomas and William Conti as papal envoys to Constantinople. The differing priorities and conceptions of the Byzantines and Latins contributed to the petering out and eventual failure of the negotiations: a 1357 letter by John V remained unanswered by Innocent VI until his death in 1362.