Quote Originally Posted by CBR View Post
Hannibal took a big but calculated risk with his cavalry. He put all his heavy cavalry on his left wing and let the Numidians handle the right wing. The Numidians would never have defeated a similar size of Roman allied cavalry if the allied cavalry had attacked but (and this is me guessing) he must have assumed that the Romans would try to be defensive. He had seen the Roman army deployed just one or two days before so maybe he spotted something in how they deployed.

We should also not forget the fog of war, there were no binoculars and lots of dust so there was a good chance that the Romans would never notice the weak right wing.

The concave infantry formation is more up for debate as historians don't agree on what happened. I don't think there was any planned retreat and the losses among the Celts suggest a tough fight and rout with many being cut down. But the formation meant the Roman infantry would not just move forward when in pursuit but also inwards. That would increase the disruption and give a better chance for his Africans in their counter attack.
But there lies the problem I brought up before, Varro made his formation deeper instead of longer, Hannibal's cavalry could not have charged the infantry, we have hindsight but didn't the Romans come up with the standard depth and length of their maniples as a result of centuries of experience?

I agree with you that Hannibal had the advantage of being just a soldier with other soldiers; he never had to factor in or care about if any of them survived and could sacrifice formations for victories to his hearts content, the Romans however were elected politicians leading many of their constituents into battle, and had to worry not only about victory but about being scene to do everything they possibly could to bring a maximum amount of soldiers home alive. Ironically against an enemy like Hannibal trying to plan for a scenario of returning as many people home as possible actually meant doing everything exactly by the book/the standard rules and Hannibal was an expert at defeating Romans who played by the rules.