The main trouble with U.S. foreign policy in the last half century is that it has too seldom been guided by self-interest, too often by "impractical idealism." So concludes the State Department's George F. ("Mr. X") Kennan, who left his job as State's top policy-planner last year for a sabbatical at the Institute for Advanced Study in Princeton. Ever since the U.S. blundered into global responsibilities in the Spanish-American War, says Kennan, its tendency has been to live in a dreamy haze, preaching moral principles but neglecting to keep the military strength to make its voice important—until crisis was upon it.
In...