It has become one of the iconic images of the Second World War—those battle-weary Marines struggling to raise the Stars and Stripes atop the highest peak on Iwo Jima. On Okinawa, a few months later, a different Marine division, even more bloodied, drew inspiration from comrades who in the midst of the fighting raised another flag—the Stars and Bars of the Confederacy. Those Marines were mostly Southern boys, of course, but no less proud to be U.S. Marines. And they were not unusual in their mixed loyalties.

Only a few weeks earlier, in April 1945, American troops commanded by Virginia-born Matthew Ridgway had surrounded a German army in the Ruhr. To coax his German counterpart to surrender, General Ridgway sent a note reminding him that exactly 80 years before, a commander facing similar circumstances had chosen “an honorable capitulation.” To drive home the point, Ridgway offered this characterization of the commander who established this precedent: “Neither history nor the military profession records any nobler character, any more brilliant master of warfare, any more dutiful subordinate of the state, than the American General, Robert E. Lee.”

We should pause over Ridgway’s remarkably complacent deployment of that phrase “dutiful subordinate of the state,” and mark the honorific, “American General.” These might seem particularly odd characterizations for the commander of a rebel army, and Ridgeway’s German counterpart was not moved. Rather than “honorable capitulation,” Field Marshall Model instructed his troops to try to escape as best they could. He made his own escape a few days later by blowing his brains out with his service revolver. He had a somewhat different sense of honor than Robert E. Lee.

Whatever it does for Europeans, we Americans remain fascinated by our Civil War. And with reason. It was the first war in which railroads, telegraphic communications, and industrial production in the rear allowed commanders to deploy large armies on short notice and keep them supplied for extended periods. The resulting battles were more like those waged in Europe in the world wars of the next century than like any battles of earlier times. More Americans died in the Civil War, in fact, than in both world wars put together.

Yet for all its intensity, the American Civil War did not generate massacres and atrocities against civilians on anything like the scale of domestic conflicts elsewhere, let alone on the scale of the world wars in Europe. The war mobilized popular resolve in a way that was then unprecedented, yet it left room for a kind of chivalry between rival commanders, or at least some notion of limits imposed by the soldier’s honor.

Still, for all its elements of restraint, the Civil War, by the time it reached its climax, had changed the self-understanding of Americans on both sides of the conflict. Having denied at the outset that the Constitution authorized secession, the North ended by imposing military rule on the South, not to restore but to “reconstruct” Southern states before allowing them to participate again in national politics. Amendments to the Constitution abolishing slavery and providing general guarantees against deprivations of rights by the states made the national government, for the first time, the ultimate guarantor of citizens’ rights. Meanwhile, the South, having rallied to the cause of states’ rights, fought a war in which Southern nationalism often superseded the claims of the “sovereign” states. Yet in the long run, the memory of the war threaded Southern pride into the larger tapestry of American nationalism—as we can see from General Ridgway’s appeal.

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It would be a considerable overstatement to say that Nicholas and Peter Onuf, in their new book Nations, Markets, and War, have now offered us a clear explanation of how this came about. Focused argument is not one of the strong points of this volume. The subtitle, Modern History and the American Civil War, actually exaggerates the degree of focus here. After an initial 50 pages in which they talk about Aristotle and medieval Scholastics and the fathers of the Reformation—for reasons I could not follow—they settle down to another hundred pages of discourse on various aspects of “modern history.” The book is half over before they finally get to the sectional conflicts in America that gave rise to the Civil War.

It may be that Nicholas, a professor of international relations at Florida International University, and Peter, a professor of American history at the University of Virginia, each felt he had to indulge his brother in some cherished digressions. The text is often learned and intelligent but it is not well digested. It invokes a variety of concepts and theories without taking the time to elucidate any of them with satisfying clarity. It nods at a whole series of historical developments without developing any narrative continuity of its own.

Yet the Onufs do, in the course of their rambling exposition, bring out some very central and important questions about the way the modern world understands itself and especially the way America has come to see itself. Their central concern is the ambiguous notion of national independence—a notion presupposing, in a somewhat paradoxical way, that the world is already organized along lines that make independence a recognized and reliable category.

We tend to take this idea for granted. It is in the Declaration of Independence, after all—that we are “among the powers of the earth” entitled by “the Laws of Nature and of Nature’s God” to a “separate and equal station.” But as the Onufs remind us, this doctrine of an international system made up of separate and equal states had been around (at least in published treatises) for only a few decades before the American Revolution, and it was by no means generally accepted in Europe even then. As they point out, the most widely recognized new text on the law of nations, in the period between the American Revolution and the American Civil War, was the work of an American—Henry Wheaton, who before his diplomatic career had been court reporter for John Marshall’s Supreme Court.

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One of the great issues in international politics in that era was the relative benefits to be gained from free trade. It was an issue that increasingly divided North and South in antebellum America. As the Onufs demonstrate, disputes about the tariff were also disputes about the fundamental character of international relations—and about the meaning of nationality, even in America itself.

Federalists and then Whigs, arguing for a protective tariff, often conceded that free trade was good for all participants. But mutually beneficial trade depended on peace, and the Atlantic was repeatedly closed to American trade during the long series of wars from the French Revolution to the final defeat of Napoleon. If it did not develop internal means of supply, warned tariff advocates, the American economy would be crippled in every new war—and wars, they argued, were bound to recur. Tariffs would not only reduce American dependence on foreign trade but help finance “internal improvements”—roads, canals, river and ocean ports-which would facilitate internal trade within the United States, where peace was assured by federal authority. Some of the tariff could also finance federal military spending, particularly on naval ships and coastal fortifications, to ensure that foreigners did not threaten America’s internal peace.

Southerners, in arguing against the tariff, advanced a different view of the world. Trade would promote peace, they insisted, because European nations would not want to risk anything that threatened mutually beneficial trade relations with their American partners. Northern tariff advocates warned, in reply, that without more internal development of its own, the United States would be doomed to trade on unequal terms—subordinated, in effect, to terms imposed by an informal commercial empire still based in London. Southerners responded that a high tariff would subordinate Southern states to a commercial empire based in New York and Philadelphia. So, as writers in the North stoked nationalist fear of British domination, Southern pamphleteers promoted a regional identity rooted in fear of the North.

The idea of secession became plausible when its advocates could present it, not as the desperate recourse of one or two aggrieved states, but as the response of a whole region, large enough to form a powerful new nation in itself. What made it plausible to think all those states would respond in the same way was, of course, that they were all slave states. The Onufs do not minimize the importance of slavery—nor, as they make clear, did Southern writers at the time. On the eve of the Civil War, Southerners were no longer content to depict slavery as a regional economic interest entitled to protection. Instead, slavery was increasingly presented as the foundation of a superior way of life.

By the time the argument reached this extreme, with its glorification of racial mastery as a way of life, Southern nationalism might appear a kind of precursor of European fascism. Yet as the Onufs describe it, the antebellum Southern outlook still conceived itself to be grounded in Enlightenment rationalism and biblical Christianity. Southerners imagined that they were uplifting barbarous people through compulsory servitude—not asserting the will to power of the Southern race. They even imagined that Southern independence would be recognized by Europeans and strengthen trends toward a more peaceful world overall. They thought that slavery at home could be the basis of harmony and peace abroad.

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Principally a work of intellectual history, Nations, Markets, and War never compares arguments pressed by regional advocates of that era with the more detached assessments that might now be offered by economic or diplomatic historians. And the book makes no effort to carry its story past the outbreak of war in 1861. But it does not require much specialized learning to see that history, even immediately following 1861, did not bear out the thinking of Southern advocates. Whether our experience since then bears out the alternative view—of national cohesion from international competition—is a more complicated question.

It says something that three generations later, an American officer corps drawn so heavily from the South was prepared to have the army’s main battle tank named for General Sherman. (The “Lee tank” had not performed well in early battles in North Africa.) It says something, too, that the rest of the American military readily accepted Southern commanders and did not begrudge Southerners their regional pride. No one was punished for that Confederate flag-raising on Okinawa.

Nations, Markets, and War shows that, apart from economics and military success, perceptions of interest and identity play a large role in the building of nations. The defense of nations also has something to do with pride. We count on it without thinking about it, and it may not bear too much thought: it may be that it is, if not irrational, still, ultimately, mysterious.