AP Photo

THE AIM in any successful counterinsurgency is to support and strengthen a sovereign and friendly government. The inherent paradox is that use of US military power, or even US diplomatic leverage, to achieve that aim undercuts the perceived legitimacy and sovereignty of the government it seeks to support. Enemies exploit this paradox to their benefit, labeling US troops as occupiers and governments allied with us as puppets, undeserving of support from their own people.

From Vietnam to Pakistan to Iraq and now Afghanistan, this is a lesson the United States continues to get wrong - making short-term decisions with unintended long-term consequences.

In 1963, the United States supported a coup against the corrupt but allied president of South Vietnam, without asking what...