In other words, what we know for sure is entirely limited, and all the rest is basically opinion.
The Ghosts of Cannae: Hannibal & the Darkest Hour of the Roman RepublicThe factor that made him so powerful was also his greatest liability.
The Fall of the Roman Empire: A New History of Rome and the BarbariansRhino-mounted Bantu shock troops could have overthrown the Roman Empire. It never happened.
Guns, Germs, and Steel: The Fates of Human Societies