Defence in depth in order to retreat successfully, and they assume that the defender's morale will recover from the retreat. A possible early example of this came at the Battle of Cannae in 216 BC, when Hannibal employed this manoeuvre in order to encircle and destroy eight Roman legions, but that is disputed by some historians. Edward Luttwak used the term to describe his theory of the defensive strategy employed by the Late Roman army in the 3rd and 4th centuries AD. Later examples of defence in depth might be European hill forts and the development of concentric castles. In those examples, the
Battle of Utica (203 BC) and the reconquest of the parts of Sicily that had been temporarily lost after the battle of Cannae, the Romans secured a base for a naval assault on Carthage. They made use of that by carrying out a number of raids on African soil in 208, 207 and 205 BC. Since 206 BC, when Scipio Africanus finally expelled the Carthaginians from Iberia (see the battle of Ilipa), he was preoccupied with the idea that Africa should be the next target. To this end, he concluded an alliance with Syphax – one of the most powerful Numidian rulers at the time