Each summer, when the President goes on vacation, the White House generally informs the media about the reading material he has taken with him—often trying to impress by listing serious and weighty tomes. In fact, the Chief Executive is probably reading a cheap murder mystery in between rounds of golf. Good for him.

Still, there is at least one serious work that should have been slipped into President Bush’s travel bag this summer: Eliot Cohen’s Supreme Command: Soldiers, Statesmen, and Leadership in Wartime. Cohen, a Professor of Strategic Studies at the Johns Hopkins University’s School of Advanced International Studies, uses case studies of four great leaders—Abraham Lincoln, Georges Clemenceau, Winston Churchill, and David Ben-Gurion—to demonstrate the character and principles that are required to lead democratic peoples to military victory.

Cohen’s analysis succeeds at several substantive levels, in addition to being a great read. Most obviously, it is a work of political science (properly understood) that explores the topic of civil-military relations. For the United States, the central problem of civil-military relations is not to prevent a military takeover of the state. Rather, it is finding the proper relationship between the preparation and use of force, on the one hand, and the ends of policy, on the other. For at least three decades, the "normal" American theory of civil-military relations holds that the healthiest and most effective form of civilian control of the military is that which isolates soldiers from politics but gives them a free hand in military matters. Civilians should not ask too many questions (much less give orders) about military tactics or operations, measures of success and the use of hardware. They should not seek to promote, dismiss or interact with anyone but the most senior officers. Civilian leaders should set clear but general strategic objectives and then leave the military as much latitude as possible to achieve these goals.

According to advocates of the "normal" theory, the wisdom of this approach was proven in the negative sense during the Vietnam War, when "abnormal" interference by civilians supposedly tied the hands of the military by limiting the geographic scope of the war, picking bombing targets from the White House, and so on. The theory is said to have been vindicated positively by the Gulf War in 1991, when the administration of George H. W. Bush ostentatiously avoiding interfering with the conduct of military operations against Iraq.

Cohen takes a very different view. He follows the Prussian military theorist Carl von Clausewitz, whose oft-cited aphorism "war is a continuation of politics by other means," is better translated, "war is not merely an act of policy but a true political instrument, a continuation of political intercourse, carried on with other means." For Clausewitz there is no field of military action — however small — that might not be touched by political factors. Civilian leaders must therefore make every effort to bend military operations to serve the end of politics (even admitting that the "fog" and "friction" of war makes such a relationship difficult to establish in practice). There is no arbitrary line dividing the civilian and military sphere, no neat way to create a distinctive and separate military dimension. As Churchill wrote, "the distinction between politics and strategy diminishes as the point of view is raised. At the summit, true politics and strategy are one."

But isn’t such meddling by civilian amateurs bound to interfere with the professional conduct of the war? Cohen acknowledges that for a politician to try to dictate military action is almost always folly. But the entire field of military activity must remain open to civilian oversight. When and where to exercise this oversight is a matter of prudence.

Prudence, of course, is the province of the statesman. Cohen observes that contemporary political scientists unfortunately have lost their sense of the practical. "A belief in the greatness of statesmen," Cohen writes, "puts in jeopardy theories built on descriptions of social forces or institutions, or systemic explanations such as Ôrational choice.’" In contrast, Cohen "unabashedly accept[s] the notion that there are, occasionally, great statesmen whose skill in the policies of war exceeds those of the average run of political men and women."

This leads to the case studies of the four great wartime leaders from different times and nations, and with very different backgrounds. Lincoln and Churchill will be familiar to American readers. Clemenceau — famous for the observation that "war is too important to be left to the generals" — entered the French government as premier in 1917 and breathed a spirit of resistance into that exhausted country during the latter stages of World War I. Ben-Gurion was the most important political leader of the campaign to create and defend the state of Israel after World War II.

Each of these leaders grappled with a different set of problems in attempting to impose civilian direction on the conduct of military operations. Cohen highlights Lincoln’s search for a general whose concept of war mirrored his own (Grant). Clemenceau intervened to balance contradictory impulses on the part of equally competent military leaders (Foch for the offensive, Petain for the defensive). Churchill relentlessly challenged his military leaders for choices and action when Britain’s strategic position seemed hopeless. Ben-Gurion forced his military commanders to make the transition from an insurgent to a conventional warfighting capability in the midst of ongoing military operations.

What do these statesmen have to teach us about the civilian role? Churchill said it best: "It is always right to probe." Instead of adopting a hands-off policy, he and the others sought to master the details of war to the point where they could ask intelligent, hard, and uncomfortable questions of military officers. None dictated to his subordinates: they might coax or bully, but all tolerated and indeed promoted men who disagreed with them. Cohen describes this process as "an unequal dialogue." Both sides expressed their views bluntly and often contentiously, while the final authority of the civilian leader was unambiguous and unquestioned. Rather than following the "normal" theory of civil-military relations, which reserves dialogue for only the beginning and end of a war, these leaders insisted on interacting constantly with the military professionals throughout a conflict.

To be sure, great statesmen make mistakes. But military experts might be equally mistaken—Cohen details these errors—and if left unchallenged, their failings would only be compounded during the course of the war. Even the best of commanders will have a restricted point of view, which is understandable because of their responsibility for the conduct of actual, specific operations. The statesman’s task is to comprehend the full scope of military action and to decide when political considerations must supersede or redirect legitimate, even pressing military concerns.

Nations, Cohen writes, are led and ruled by words. In the best of nations, these words reflect and ennoble deeper truths about the best way of human life. Each of these statesmen had mastered the arts of speech and writing. They understood the importance of words that explain as well as inspire. For example, Churchill’s famous wartime rhetoric ("we shall fight on the beaches") represented only a small portion of his public discourse. He spoke at great length to the British and allied peoples to lay out the course as well as the meaning of the war, including those details of operations and strategy which he could safely share. In this way, ordinary people became part of the great, democratic dialogue between the civilian and military leaders.

So what of Vietnam? Cohen argues persuasively that the United States failed in Southeast Asia not because American leaders immersed themselves in too much detail but because they looked at the wrong details and drew the wrong conclusions. President Johnson and Secretary of Defense McNamara did not test the military’s preferred strategy—attrition warfare, search and destroy—against what was actually happening in the field. They did not ask whether the military organizations in Washington or in theater were properly designed and tasked. They did not cross-examine their subordinates or force them into debates with other professionals, inside and outside government, who took a different view. Cohen does not take a position whether the war could have been won if the Johnson administration followed this approach, but clearly it would have avoided at least the scale of the fiasco that followed.

All this begs the question: if George W. Bush happens to read Supreme Command during his summer vacation, what should he learn and do? Statesmanship is not a formula, a set of maxims which if followed leads infallibly to success. ("Lincoln fired commanding generals every six months, so I guess it’s about time to dismiss the Chairman of the Joint Chiefs.") But surely one point must be clear: the corporate, hands-off management style that Bush has said that he generally prefers won’t cut it here. Ask the tough questions, Mr. President. Don’t accept the easy answers at face value. Become a pain to your generals. And enjoy your round of golf.

Patrick Garrity is an Adjunct Fellow at the Ashbrook Center.