Ramiro's first attempt to take Graus, the northernmost Muslim outpost in the valley of the Cinca, took place in 1055, probably in response to the defeat of García Sánchez III of Navarre at Atapuerca the year before (1054), which placed Ferdinand I of León and Castile in a commanding position against Ramiro's western border and the Muslim Taifa of Zaragoza to his south. His first expedition against Graus failed, and in 1059 Ferdinand succeeded in extorting parias (tribute) from Zaragoza. Ramiro marched on Graus again in the spring of 1063, but this time the Zaragozans had with them 300 Castilian knights under the infante Sancho the Strong and (possibly) his general Rodrigo Díaz de Vivar, better known as El Cid. The presence of the Cid at the battle is based on a single source, the generally