Tonight’s episode of On Hannibal’s Trail deals with a moment in history when the fate of the world hung on a knife edge. In ‘Hannibal the Great’ at 830pm on BBCFour we follow the Carthaginian commander around Italy and re-enact his big victories against the Romans. As we cycle away from the battlefield of Cannae, we ask; why didn’t Hannibal march on Rome after this massive victory and finish the war by taking his enemy’s capital?

There is enough evidence to argue that if Hannibal had done this the war could have been won. His decision not to probably surprised a lot of his men who were waiting for the opportunity to sack the city.  Afterall, Hannibal had urged his men on in the freezing Alps with the promise that they were climbing Rome’s very walls. And wasn’t this a general famous for taking the initiative and reacting quickly to take advantage of events?

Most modern historians accept Hannibal’s decision not to advance on Rome after Cannae with a combination of explanations: Hannibal wasn’t prepared for siege warfare; Rome was well defended and still had reserves of manpower; destroying Rome wasn’t part of Hannibal’s plan – instead he wanted to isolate Rome from its allies and force her to accept peace on Carthaginian terms.

But what if he had?

Livy portrays Hannibal’s cavalry, Commander Maharbal urging him on: “Sir!…within five days you will take your dinner, in triumph, on the Capitol. I will go first with my horsemen…You have but to follow.”

But Rome is 250 miles from Cannae

Historians often say Maharbal was being unrealistic and doubt his cavalry could reach Rome in five days. They argue it was impossible to take Rome with a few thousand men and even when the rest of the army arrived at least two weeks later, sieging the city was an unrealistic objective.

But if we take Maharbal’s quote on its merits for a moment. As an example of what a horse can do, in Auburn, California the Tevis Cup Endurance Race requires horses to complete 100 miles in one day. The best horses do it in under 12 hours. Some horse experts think that, with regular rest stops and over terrain that wasn’t too rough, a quality horse could ride about 60 to 75 miles per day for a week. The Numidian cavalry and their mounts were the best in the known world, even taking into account recovery time after the battle, it looks like Maharbal’s estimate of what they could do – 50 miles per day – is spot on. Rome was a realistic target.

They would have been closing in on the city’s gates while the Romans were still absorbing the result of the battle. In that confused and panic stricken atmosphere fuelled by a lack of information about their worst defeat ever, the arrival of Hannibal’s cavalry could have been devastating. And as those cavalry were spotted, news of yet another defeat would have been coming in. Polybius writes that only days after Cannae, Rome’s only other army in the field was destroyed in Cisalpine Gaul. So in the days following Cannae, it’s possible that Rome’s only defence was its garrison and 1,500 sailors in the city’s port of Ostia. Who’s to say that a panic stricken citizenry wouldn’t have opened the gates?

Livy, is very clear about Rome’s situation: “That day’s delay is well judged to have been the salvation of the city and its empire.”

Viewed from the perspective of the 3rd century BC, Rome wasn’t the all conquering people it would become later. In the aftermath of Cannae, some Senators were trying to raise troops and restore order, but they were also placing guards at Rome’s gates to stop people fleeing the city in panic. And even before orders were sent to fetch the 1,500 sailors at Ostia, it was deemed more urgent to carry out human sacrifices. Two Gauls and two Greeks were buried alive in the cattle market to appease the gods, hardly the response of a people confident in ultimate victory. “Never” writes Livy, “without there actually being an enemy within the gates had there been such terror and confusion in the city.”

Who said Siege Rome?

So the gates may well have been opened to Hannibal if his cavalry had appeared in the week after Cannae. If not, a siege or blockade of Rome could have followed when the rest of Hannibal’s army arrived. If Hannibal’s aim was to separate Rome from its allies, one way of doing that could have been to blockade Rome. This could have been a rallying cry for Celtic tribes in the north and Italians and Greeks in Italy, eager for plunder and revenge against their Roman oppressor. Who knows what would have happened?

But Hannibal didn’t push his hand after Cannae and so in the small world of Woodbrothers we had a final, episode 6 to make.