The Battle of Morella (14 August 1084×88), southwest of Tortosa, was fought between Sancho Ramírez, King of Aragon and Navarre, and Yusuf al-Mu'tamin, King of Zaragoza, while the former was engaged in a campaign of conquest against the latter. All surviving sources for the battle are either later by a generation or literary in character, and they are confused on the chronology and dating of the event. The encounter was a defeat for Sancho and sparked a brief reversal of fortunes in the Navarro-Aragonese Reconquista. The Castilian hero, Rodrigo Díaz de Vivar, El Cid, was a general for al-Mu'tamin at the time. According to the Aragonese Crónica de San Juan de la Peña (c.1370), Sancho later sought out El Cid, who had also defeated his father in the Battle of Graus (1063), and defeated him in the year 1088. However, the Crónica is the only source mentioning such an encounter and, as it was written three hundred years later, most leading scholars give no credence to this claim, which was probably intended to justify the prerogatives of Peter IV of the Crown of Aragon.