In the succeeding years, Polybius resided in Rome, completing his historical work while occasionally undertaking long journeys through the Mediterranean countries in the furtherance of his history, in particular with the aim of obtaining firsthand knowledge of historical sites. He apparently interviewed veterans to clarify details of the events he was recording and was similarly given access to archival material. Little is known of Polybius' later life; he most likely accompanied Scipio to Spain, acting as his military advisor during the Numantine War.