Guerra de Sucesión Castellana
During the War of the Castilian Succession, he served as a diplomat for Castile, assisting in the establishment of the Santa Hermandad in 1476 and the organization of naval reinforcements for the defense of Gran Canaria, a Castilian possession, in 1479. Palencia remained a strong supporter of Fernando but Isabel's councilors, especially Pedro González de Mendoza, were suspicious of Palencia's loyalties. In the 1480s Isabel appointed Fernando del Pulgar as her royal chronicler and Palencia was effectively stripped of political influence.