In many respects, as he confessed later in life, McNamara’s mistakes were mistakes of omission not commission. They were mistakes nonetheless. His mistakes raise important counterfactual questions. What if McNamara had inherited another model for civil-military relations? What if the State Department had been stronger? Could a counterinsurgency strategy have worked in South Vietnam? Could different funding arrangements in Washington have produced different outcomes? What if Johnson had been less of a New Dealer? What if McNamara had defined “loyalty” differently? What would President Kennedy have done?