Walter Lippmann, U.S. Foreign Policy: Shield of the Republic (1943)

Shield of the Republic formulated what might be called the Lippmann equilibrium, which has become the standard of American realists: "Foreign policy consists in bringing into balance, with a comfortable surplus of power in reserve, the nation's commitments and the nation's power. I mean by a foreign commitment an obligation, outside the continental limits of the United States, which may in the last analysis have to be met by waging war. I mean by power the force which is necessary to prevent such a war or to win it if it cannot be prevented. In the term necessary power I include the military force which can be mobilized effectively within the domestic territory of the United States and also the reinforcements which can be obtained from dependable allies." If this strategic equilibrium could be brought into being, American foreign policy would command domestic support. On the other hand, if American commitments exceed American power, the resulting insolvency—"the Lippmann gap"—would lead to deep political dissension.