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
Perusia Perusia The ancient Perusia, now Perugia, first appears in history as one of the 12 confederate cities of Etruria. It is first mentioned in the account of the war of 310 or 309 BC between the Etruscans and the Romans. It took, however, an important part in the rebellion of 295 BC and was reduced, with Vulsinii and Arretium (Arezzo), to seek for peace in the following year. It seems the city was in the Antonii's clientela since this period, as it was said by historians during imperial times. In 216 BC and 205 BC it assisted Rome in the