Battle of Cannae required Hannibal to subdue a considerable part of the hinterland to cut the enemy's supplies and secure his own. Even after the tremendous losses suffered at Cannae and the defection of a number of her allies, Rome still had abundant manpower to prevent this and maintain considerable forces in Iberia, Sicily, Sardinia and elsewhere despite Hannibal's presence in Italy. Hannibal's conduct after the victories at Trasimene (217 BC) and Cannae, and the fact that he first attacked Rome only five years later, in 211 BC, suggests that his strategic aim was not the destruction of his foe but to dishearten
Early Middle Ages had broken down, and the Roman army comprised mainly barbarians and soldiers recruited for a single campaign. The general decline in discipline also led to the use of smaller shields and lighter weaponry. Not wanting to share the glory, Eastern Emperor Valens ordered an attack on the Therving infantry under Fritigern without waiting for Western Emperor Gratian, who was on the way with reinforcements. While the Romans were fully engaged, the Greuthung cavalry arrived. Only one-third of the Roman army managed to escape. This represented the most shattering defeat that the Romans had suffered since the Battle of Cannae (216