With the Iraq War now in its fourth year, its merits are still contested by leading politicians in the U.S. and elsewhere. And revelations suggest that the president’s secretary of state, Colin Powell, had opposed going to war. Historians have often analyzed the relationship between presidents and their advisors, but rarely the influence of those counselors who have dissented from the views of the chief executive. Mark J. White considers the question of alternative policies by examining the response of presidents, from Harry Truman to Lyndon Johnson, to dissent within their own. Mr. White fashions a provocative interpretation of America’s role in the cold war and questions about the potential effectiveness of policies that might have been.