When the Carthaginian cavalry attacked the Romans in the rear and the African flanking echelons assailed them on their right and left, the advance of the Roman infantry was brought to an abrupt halt. The Romans were henceforth enclosed in a pocket with no means of escape. The Carthaginians created a wall and began to systematically massacre them. Polybius wrote: "as their outer ranks were continually cut down, and the survivors forced to pull back and huddle together, they were finally all killed where they stood."