The King of Castile, being in such disagreement with the King of Aragon in the year 1359, was keen to build a great armada with which to attack his kingdom. Although he had quite a big fleet, comprising both naos and galleys, he was not yet satisfied with it. Consequently, he sent his lord chamberlain Juan Fernández de Henestrosa to his uncle the King of Portugal to ask that the ten galleys which he had been promised in aid against Aragon be made ready, as he was in great need of them.

The King of Portugal was happy to do this and immediately ordered ten galleys and a galliot to be equipped with good men, with his admiral Master Lançarote on board. When the King of Castile received word that the ten Portuguese galleys were ready, he left Seville in the middle of the month of April with his whole armada made up of eighty naos with forecastle, twenty-eight galleys of his own, two galliots and four smaller vessels, plus three galleys belonging to the Emir of Granada, which he had sent in aid at the king's request.

The king waited for the Portuguese galleys in Algeciras for fifteen days, but when he saw they were not coming, he left for Cartagena and waited there for all his ships to arrive. He then attacked Guardamar, taking the town and the castle. From there he made his way along the coast, attacking a number of places, but without success. He arrived at the River Ebro near Tortosa, a town belonging to Aragon, where the ten Portuguese galleys also arrived, sent in aid by his uncle the King of Portugal. The King of Castile and his whole fleet were very pleased at this. The king then had in total forty-one galleys, as well as the small foists.

The king left there with the whole armada and arrived on the eve of Easter at Barcelona where the King of Aragon was living. There were twelve armed galleys there that could not be captured because they were positioned alongside the city, from where they were defended with many crossbows and cannons. The king spent three days at Barcelona with his whole fleet and then went to the island of Ibiza and besieged a fine town of the same name.