Victor Davis Hanson’s latest book is a macabre warning to an aging America as it closes in on its 250th birthday. The warning comes in the form of a graphic depiction of the hideousness of war and the terrifying state of those who suffer ignominious defeat. However different the four societies described in the book were, be they Thebans, Carthaginians, Byzantines, or Aztecs, each was blinded by the illusion of invincibility. Hanson shows that such an illusion is so persistent that even as the conquered were being slaughtered, they continued to think: “It cannot happen here.” Thebes, the 4th century...