Robert L. O’Connell, Of Arms and Men: A History of War, Weapons and Aggression (New York and Oxford, 1989), p. 81
579
E. N. Luttwak, The Grand Strategy of the Roman Empire (Baltimore, 1976), pp. 25–26; 41–42; 46–47; Susan P. Mattern, Rome and the Enemy: Imperial Strategy in the Principate (Berkeley, 1999), pp. xii; 222
