Although disappointed not to inherit the whole realm, the eldest prince, Don Sancho, dared not oppose his father's will, until one of his brothers proceeded to dispossess one of their sisters.

Under the plea that the promise made to their father had already been broken, Don Sancho now set out to conquer the whole realm, but proved so unfortunate in his first battle as to fall into his brother's hands.

There he would have remained for the rest of his life, had not the Cid delivered him, taken his captor, and confiscated his realm in Sancho's behalf.

Hearing this, the third king, Alfonso, clamored for his share of his brother's spoil, and, as none was allotted him, declared war in his turn.

In this campaign Sancho proved victorious only when the Cid fought in his behalf, and the struggle resulted in the imprisonment of Alfonso, who would have been slain had not his sister asked that he be allowed to enter a monastery.