Diego de Valera
Mosén Diego de Valera was a Spanish nobleman, author, and historian who has been described as having had "chivalrous adventures" that took him "as far as Bohemia" where he was a participant in the Hussite Wars. He authored letters to Spanish Kings John II of Castile and Henry IV of Castile admonishing them to remember rulers who had been deposed for poor governance. He reminded the latter of various Old Testament kings who were chosen to rule, but were deposed nonetheless, and of thirteen Gothic kings who died at the hand of their vassals due to despotic government. Without necessarily approving rebellion and deposition, he implied that such was the common fate of unworthy kings. His warning did not prevent King Henry IV from being deposed in 1465.
He also wrote one of the first known books on fencing, Treatise on Arms.Books
