Libya under Moammar Gaddafi was not Germany under Adolf Hitler. But lives were at stake, mass murder was threatened and the man doing the threatening was capable of unspeakable acts of terrorism. Did any of this have anything to do with our vital national interests? Not really. But we had the wherewithal to avert the killing. That gave us the moral obligation to do so.

U.S. policymakers now grappling with the question of America’s role in the world ought to look to the past as well as the future. We were once an uncaring nation, not selfish by any means, but tone-deaf to the cries of victims elsewhere. We defined our national interests narrowly and dismissed morality as the preoccupation of amateurs or special-interest pleaders. Larson’s book is instructive on this score. Martha Dodd may have slept with the enemy, but, in moral terms, she was no worse than the country she represented. It just slept.