In the 14th century Peter I and Peter III reigned over Castille and Aragon. They have gone down in history as the cruel one (Peter I) and the ceremonious one (Peter III). These nicknames are due to the Chronicles, written about these two kings; Pero Lopez de Ayala's work about Peter I and the other written by Peter III, helped by other writers. These works are therefore political acts- the one, written in Catalan- aiming to justify the Sovereign's actions- whereas on the contrary, the other, the Castillian Chronicle, intended to criticize them.These works are therefore vital as it is through these that the reader can form his own judgement of people and events. However, before attaining this aim, a study of the actual act of writing must be carried out. People should question its final form, reflect upon its reach and indicate what it should offer. The stakes are high as it is a question of defining the meaning of the expression writing history, at the end of these Middle Ages.