A theme that Geoffrey Chaucer develops through these two excerpts is that of treachery, since both King Peter of Spain and King Peter of Cyprus were betrayed and their lives ended tragically. King Peter of Spain was betrayed by a man named Bertrand, who had agreed to protect him in exchange for a great compensation, but who eventually handed him over to his half-brother, Henry, who promised him an even greater reward and who assassinated Peter in his tent in 1369, becoming the new king. This is narrated in the excerpt, where Bertrand is compared not with Oliver of Charlemagne, friend of Charlemagne, but with the knight that betrayed him ("No, Oliver of Charlemagne... such a trap!").
Peter I of Cyprus devoting his short yet intense life to fight Islam, and he led the short yet devastating Alexandrian Crusade, but his life ended abruptly. Betrayed by his wife and by some of his closer knights, he was assassinated in his bed also in 1369. This is also referred in the poem ("That conquered Alexandria... on thy bed!").
To sum up, both excerpts revolve around this theme, which they present very similarly: after emphasizing the deeds of the two historical characters, they finalize by regretting their tragic endings.
