It is said that his decision to fight was spurred on when a woman in his town was raped by a French soldier; Díez afterwards killed the offender.

During the spring of the same year, his field of action extended along the mountains in Gredos, Ávila, and Salamanca, and also in the provinces of Cuenca and Guadalajara.

The damage to Napoleon's army was considerable, to such an extent that Joseph Léopold Sigisbert Hugo, a French general, was given the duty to "pursue exclusively" Díez and his guerrillas.

Later, Fernando VII would approve the construction of a commemorative pyramid in Alcalá in honor of the victory, only to order its destruction in 1823, deriding it as a symbol of a "liberal".

When King Fernando VII returned to Spain and restored absolutism, he took measures against those he considered "liberal enemies", among them Díez, who was exiled to Valladolid.

In 1820, the revolution of Rafael de Riego commenced, and Díez took up arms - but this time against Fernando VII's royal troops.

In 1823, during the Absolutist Reaction, a French Army (the so-called Hundred Thousand Sons of St. Louis) invaded Spain to restore absolutism,[2] the liberal regime fell, and Díez fled to Portugal.

The magistrate in Roa de Duero, however, had already ordered Díez's execution, which was carried out on August 20, 1825, in the central plaza of the village.