The escape of Aeneas after the Trojan war, his stay in Carthage and the emergence of his descendants are narrated in the second part of the General estoria, by Alfonso X. The fragment is preserved in six manuscripts, in addition to an archaic witness (Mb) of this universal history. The passage also corresponds to two chapters transmitted in Estoria de España, whose codex H attests to the precedence of the EE fragment over the one found in the GE. Alongside an edition of the excerpt from Mb, we investigate how comparing it with the six other manuscripts demonstrates the different stages of the Alfonsine compilation process, through expedients such as abbreviatio, amplificatio, ordinatio, and the inclusion (or omission) of declared references to the sources used. Furthermore, since Mb is also a witness to the Historia troyana of Peter I of Castile, we discuss how the addition of the narrative about Aeneas and Brutus at the end of the composition suggests a political and typological appropriation of ancient histories in fourteenth-century Castile.