In 1134 William VI was with King
Alfonso VII of León and Castile when he besieged and took
Zaragoza. There he paid
homage to and became a
vassal of Alfonso. The submission of
García Ramírez, the king of
Navarre, as well as "many other nobles from Gascony and France had become his vassals" was the justification for Alfonso's coronation as
Emperor of Spain in 1135. Among the vassals from
Languedoc only William of Montpellier is singled out by name in the
Chronica Adefonsi imperatoris, the contemporary account of Alfonso's reign: All of the nobles from Gascony and from the area up to the Rhone River, including William of Montpellier, came to Alfonso in a spirit of mutual accord. They received silver, gold, horses and many different precious gifts from him. They all became his vassals, and they were obedient to him in all things. . . He presented them with arms and other items. Hence the boundaries of the kingdom of Alfonso, ruler of León, extended from the shores of the Atlantic Ocean, near where the city of our holy patron Santiago is located, all the way to the Rhone River. In 1146 Alfonso sent
Arnaldo, the
bishop of Astorga, as his envoy to the courts of Barcelona and Montpellier, requesting them to come in August 1147 for the
siege of Almería "for the redemption of their souls". According to the
Chronica, "they received his invitation with joy [and] promised to be present alongside of the
Genoese [who were providing the fleet]." After participating in the capture of Almería, William also took part in another joint military venture: the
reconquest of Tortosa. William and the count of Barcelona were among the soldiers awaiting the arrival of the Genoese fleet at the mouth of the
Ebro on 12 July 1148. According to the Genoese account, the
Ystoria captionis Almarie et Turtuose of
Cafarus, the lords of Barcelona and Montpellier camped atop "Mount Magnara", one of two hills overlooking Tortosa, while the other foreign troops, mostly English, French and Flemish knights who had participated in the
siege of Lisbon the year before, camped on the hill called "Romelinus". After the conquest of Tortosa, one of William's younger sons was made co-lord of the city. ==Marriage and alliance with Aragon==