Don Sancho was much enraged against Don Ramiro for having aided the people of Navarre, his enemies, who very often made raids and irruptions into the territories of Castile, committing all kinds of depredations; and Don Ramiro, on his side, was very angry with Don Sancho, for he considered that he had humiliated him by having conquered Saragosa, which had been under obedience to him; and the conquest of which, he believed, only appertained to him.
The Aragonese were stationed at the Castle of Grados erected by the Moors on the bank of the river Esera, that it might serve as a defence against the invasions of the Christians, and, quitting their fortified position, they sallied forth to encounter Don Sancho, in order to demand satisfaction from him for the affront which they considered they had received.
Don Sancho asked the advice of the Cid, before replying to the demands of Don Ramiro.
"Sire," answered Rodrigo, "I do not believe that the King of Aragon denies entirely your right to compel to obedience those infidels, who acknowledged vassalage to Castile during the lifetime of your father, or that Don Ramiro denies that the Christian kings of Spain should not have equal right to seize on the territories occupied by the infidels. Explain to him with courtesy, but without in any way lowering your dignity, the reasons on account of which you considered yourself justified in attacking the Moors of Aragon, and if, not satisfied with these reasons, he should take up arms, let you do the same; sustain the general opinion, that Castile should never let itself be made a vassal by either Moors or Christians. It is certainly a painful thing to have to fight against Christians, but it is not less so that Christians should seek to reduce to vassalage Castile, which for centuries has fought against the Crescent. Remember what your father did when the Germans, who were also Christians, sought to impose vassalage on him. If at the beginning of your reign you do not gain the reputation of firmness and bravery, even though you may have to fight against Christians, you will be considered pusillanimous, and even the weakest will dare to oppose you."
This advice of Don Rodrigo was very pleasing to Don Sancho, for both their views on this subject were identical, and the King of Castile answered, in a courteous but dignified manner, the King of Aragon; Don Ramiro, however, who did not want explanations, but rather some pretext to avenge his resentment, would not listen to those of Don Sancho, but at once prepared his army for battle. Don Sancho did the same, and the fight commenced with a fury not often seen.
Don Sancho and the Cid, accompanied by Diego Ordoñez de Lara, a cavalier much devoted to the king and to Rodrigo, and by other good knights, amongst whom were Guillen of the Standard, Alvar Fañez Minaya, and Martin Antolinez, were the first that closed with the army of Aragon.
The battle lasted for many hours, and much blood was shed on both sides, but in the end Don Ramiro had to abandon the field in very great disorder. Don Sancho, satisfied with having taught such a lesson to the Aragonese, ceased the pursuit, for to follow up his victory would only cause the shedding of more Christian blood.
The Moors, however, who garrisoned the Castle of Grados, when they learned that the army had retreated, filled with dismay and with its forces much weakened, sallied forth against it and annihilated it; Don Ramiro having been killed in this battle before Don Sancho could come to his assistance, for as soon as he learned that he, whom he had just defeated as his principal enemy, was in great danger, he advanced to the place, rather distant, where the Aragonese and Moors were fighting.
The latter turned back to shut themselves up again in Grados, being much in dread of the Castilians; and, as that fortress was impregnable, and as Don Sancho had not been offended directly by those who garrisoned it, the Castilians did not consider it prudent to remain longer in Aragon, and therefore returned to Castile, satisfied with the success which they had achieved.
The people of Castile, who still deplored the loss of Don Fernando, changed their mourning into gladness on account of those glorious triumphs; hoping to find in Don Sancho a king as brave, as wise, and as great as he was whom they had recently lost.