“Christ, Edward! No!” Edward Luttwak has just lunged at me with a knife in the study of the house he shares with his wife in a suburb of obdurate anonymity near Washington, DC. He is giving an unsolicited demonstration of how to most effectively stab someone.

“Let your hand go limp, then feint a punch with your non-knife hand,” he says with gusto, his left fist fluttering around my face, “then stab into the diaphragm upwards. The