The idea of a poem in honour of Augustus was present to his mind when he wrote Georg. iii. 46,
‘Mox tamen ardentes accingar dicere pugnas
Caesaris.’
The Aeneid was commenced B.C. 29, and remained unfinished at Virgil’s death.
Servius, vit. Verg., ‘postea ab Augusto Aeneidem propositam scripsit annis undecim, sed nec emendavit nec edidit.’
His method of working at the poem is thus described by Donatus, ‘Aeneida prosa prius oratione formatam digestamque in xii. libros particulatim componere instituit, prout liberet quidque et nihil in ordinem arripiens. Ut ne quid impetum moraretur, quaedam imperfecta transmisit, alia levissimis verbis veluti fulsit, quae per iocum pro tibicinibus interponi aiebat ad sustinendum opus donec solidae columnae advenirent.’
In what order the Books were written it is impossible to decide; but Book vi. was not read to Augustus till after the death of the young Marcellus, B.C. 23.
Donatus, ‘Cui [Augusto] multo post perfectaque demum materia tres omnino libros recitavit, secundum quartum sextum, sed hunc notabili Octaviae adfectione, quae cum recitationi interesset ad illos de filio suo versus, “Tu Marcellus eris,” defecisse fertur atque aegre focillata est.’
Virgil, writing to the emperor, insists on the magnitude of the task he had rashly undertaken.
Macrob. Saturn. i. 24, 11, ‘Tanta incohata res est, ut paene vitio mentis tantum opus ingressus mihi videar, cum praesertim, ut scis, alia quoque studia ad id opus multoque potiora impertiar.’
Although in his will Virgil left instructions to Varius (and Tucca) to destroy all his unpublished manuscripts, Varius was expressly desired by Augustus to revise and publish the Aeneid.