Battle of Cannae the flanks at the crucial moment, and encircle the overextended Romans. The Romans were in front of the hill leading to Cannae and hemmed in on their right flank by the river Aufidus, so that their left flank was the only viable means of retreat. In addition, the Carthaginian forces had maneuvered so that the Romans would face east. Not only would the morning sun shine low into the Romans' eyes, but the southeasterly winds would blow sand and dust into their faces as they approached the battlefield. Hannibal's deployment of his army, based on his perception of the terrain
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