Primera Guerra Civil Castellana
In 1366 began the calamitous Castilian Civil War, which would see him dethroned. He was assailed by his bastard brother Henry of Trastámara at the head of a host of soldiers of fortune, including Bertrand du Guesclin and Hugh Calveley, and abandoned the kingdom without daring to give battle, after retreating several times (first from Burgos, then from Toledo, and lastly from Seville) in the face of the oncoming armies. Peter fled with his treasury to Portugal, where he was coldly received by his uncle, King Peter I of Portugal, and thence to Galicia, in the northern Iberian Peninsula, where he ordered the murder of Suero, the archbishop of Santiago, and the dean, Peralvarez.