his younger brother Michael, he provoked a Tatar raid into Thrace, and in the confusion sought refuge at John's court. The first documented contacts between John and Michael VIII's arch-enemy, Charles of Anjou, also date to the same time (April 1273). A commercial treaty was concluded, allowing the export of silk from Thessaly to Apulia and the import of horses from Italy, but it is clear that these contacts were also the first steps for John joining the coalition being prepared by Charles against Constantinople and its ruler. Michael VIII sought to counter the threat of a new crusade, led by Charles of Anjou and aiming at the restoration of the Latin Empire, by negotiating a union of the Roman Catholic and Eastern Orthodox churches. The Union of the Churches was concluded at the Council of Lyons in 1274, at which the Emperor's representatives were forced to recognize Papal primacy. This decision aroused passionate opposition from the Byzantine people, the Orthodox clergy, and even within the imperial family itself. Michael VIII's sister Eulogia, and her daughter Anna, wife of John's half-brother Nikephoros, were among the chief leaders of the anti-Unionists. Nikephoros, John, and even the Emperor of Trebizond, John II Megas Komnenos, soon joined the anti-Unionist cause and gave support to the anti-Unionists fleeing Constantinople. Michael VIII asked Pope Gregory X to excommunicate John Doukas, but the Pope, who was probably uncertain of the Byzantine emperor's true loyalties, refused. Michael VIII would continue to press Gregory's successors, Innocent V and Nicholas III, for the same, as well as for a dissolution of John's alliance with Charles, but without success. In 1275, Michael VIII sent an army under his brother John Palaiologos and Alexios Kaballarios against John. The Byzantines surprised John at Neopatras and laid siege to his fortress, before he could react. John saved himself by sneaking through enemy lines disguised as a lowly groom seeking a stray horse, and made his way to the Duke of Athens, John I de la Roche. Having secured 300 horsemen from him, he returned to Neopatras and scattered the Byzantine army. In exchange for this aid, however, John gave his daughter to de la Roche's son, William de la Roche, with the towns of Zetounion, Gardiki, Gravia, and Siderokastron as her dowry. In April 1277, papal legates arrived at Constantinople and forced Michael VIII, his son and heir Andronikos, and the Patriarch John