Virgil is writing the Aeneid while he is in the court of Augustus, who won the last in a series of civil wars in Rome that destroyed its republican government and created a dictatorship that would last for centuries. During Virgil's life, he didn't know that this would be the end of the civil wars and that Augustus and his successors would actually lead Rome to even greater power and glory than it had previously known. The only thing the people could know is that under Augustus" reign, things had become more stabilized and that is how Augustus wanted it to stay. When Virgil writes about the future glory of Rome, he's writing about what he hopes will happen along with writing to praise the accomplishments of Augustus such as bringing this stability to Rome as its emperor. He's also writing in favor of continuing to put Rome's fate in the hands of Augustus, which I see as Augustan propaganda. Some of the ways he adds to the propaganda of Augustus" power and glory is through Aeneas" relationship with Dido, Aeneas" visit to the underworld and the shield he receives a the end of Book VII.
The real subject of the Aeneid is the origin of Rome and Augustus. Since Virgil's epic does not go near these events in the time span the epic covers, the reader has to rely upon hearing about these important subjects through the prophecies that are references throughout the story. These references to topics going on in Virgil's time would be of particular interest to his contemporary readers. The Aeneid is written at a time where Augustus had just achieved a victory in the naval battle at Actium, where a lost would have caused permanent disruptions of peace in Rome. Augustus, just like Aeneas, is concerned about getting and keeping peace in Italy. .
The idea of "pietas", a moral sense of duty of being devoted to a purpose that lies outside oneself, plays an important role for Aeneas. Augustus also had a great sense of pietas.
