When Virgil began to write the "lliadic" half of his Aeneid, he enjoyed a great deal more freedom in setting up its action than had Homer, whose characters' lots were generally predetermined by received myth as surely as by any Fate. As a result, it is possible to achieve keen insight into Virgil's poetic design in the Aeneid by examining the particular cast he has given to the poem's action or specific variations he has introduced into his literary models.
McDermott, Emily A. "The 'Unfair Fight': A Significant Motif in the Aeneid" Classical Journal Vol. 75 Iss. 2 (1979).