Gaius Oppius was an intimate friend of Julius Caesar.
He managed the dictator's private affairs during his absence from Rome, and, together with Lucius Cornelius Balbus, exercised considerable influence in the city.
It is now generally held that he may possibly have written the account of the Alexandrian war (although the claims of Hirtius are considered stronger), but certainly not those of the Spanish and the African wars, although Niebuhr (the Danish-German Romantic era historian) confidently assigned the Bellum Africanum to him.
The writer of these latter accounts took an actual part in the wars they described, whereas Oppius was in Rome at the time.
[2] After Caesar's death Oppius apparently wrote a pamphlet attempting to prove that Caesarion, Cleopatra's son, was not actually fathered by Caesar as she claimed.