In 1968, when the U.S. was sinking into the quagmire of Vietnam, Robert McNamara resigned as Secretary of Defense and became president of the World Bank. Having retreated from the war against communism, he threw himself into the struggle against another enemy, which has turned out to be more robust and insidious: human misery so extreme and extensive that it can spread across borders in the form of marauding armies or refugees fleeing hunger and chaos.
As McNamara quickly realized, the poorest countries were all but beyond help if their citizens brought babies into the world at a rate that defied...