“History never repeats itself,” the Yale medievalist Roberto Lopez used to warn his students. “It only appears to do so, to those who do not pay attention to the details.” Most comparisons of the United States and imperial Rome operate in exactly the low-detail environment Lopez described. Rome was a republic; America is a republic. Rome had gladiators; America has football. Rome had barbarian invaders; America has illegal immigrants. Rome fell; so America must fall. What else does one need to know?

Quite a lot, actually. Analogies ought to be used to elucidate and explain, but the analogy between the United States and Rome is all too often used to scold, not to enlighten. Here is an example, a comment by a former comptroller of the United States cited in Thomas F. Madden’s new book, Empires of Trust:

The Roman empire lasted 1,000 years, but only about half that time as a republic. The Roman republic fell for many reasons, but three reasons are worth remembering: declining moral values and political civility at home, an overconfident and overextended military in foreign lands, and fiscal irresponsibility by the central government.

What does this tell us about either Rome or the United States? Uncivil as America’s political chat shows may be, they do not begin to compare with the wave of assassinations, coups, and civil wars that brought down the Roman republic. The remainder of the comparison, though less silly, is if anything even more ignorant of the realities of republican or imperial Roman politics and power. The military of republican Rome was not, in fact, overextended. And the republic was “fiscally irresponsible” only because it had no fiscal policy in any sense that we understand the term.

In its concluding years the later Roman republic resembled, if anything, today’s Russian republic more than any aspect of the United States. Its end, moreover, was very far from the end of Rome, and not exactly a tragic turn of events. The study of Rome can yield many insights, but not much in the way of forecasting the American future.

What a joy and relief it is, then, to come upon Madden’s Empires of Trust, which carries the useful subtitle, “How Rome Built—and America Is Building—a New World.” Madden, a medievalist by academic specialty but also deeply grounded in antiquity, is a genuine historian rather than a history-manipulating polemicist, and an American more interested in understanding his country than in reproaching it. He has produced a fascinating study of the mechanics of global power, written in a style so charming and witty that it will entertain even the most casual reader, but informed by a depth of learning that will impress even the most knowledgeable.

Empires, Madden notes, have been a common phenomenon in human history. An enterprising warlord puts together an effective military force, attacks his neighbors, and collects tribute from them. These empires look mighty while they last, but they seldom last long. They exist to exploit. They command no loyalty. Eventually they meet defeat, their military ceases to awe, and they collapse. The story is the same from the Assyrians to the Nazis.

As against these Ozymandian episodes, the Romans extended their dominance over a vast realm of time and space. From the middle of the 2nd century B.C.E. to the end of the 4th century C.E., a span of almost a half-millennium, they held a practical monopoly of organized force over all the world they knew. How did they do it?

One familiar answer emphasizes Roman ruthlessness. Defy the Romans, and you would end up like the Carthaginians: your men slaughtered, your women and children sold into slavery, your city burned, the ground plowed with salt.

Madden invites us to consider another answer. As the Romans saw it, he writes, they led an alliance and association of independent Italian city-states, with Rome merely first among equals. This alliance had grown up in response not to the Roman lust for power or slave labor but to genuine security needs.

A small village on a plain of many small villages, Rome had waged war to eliminate threatening enemies. The great trauma of 390 B.C.E., when the town was sacked by marauding Celts, had forced Rome’s leaders to think hard about military organization and generalship. They designed new military forms that won battles more consistently than did the forces of their neighbors.

But the early Romans, like the early Americans, were a deeply isolationist people. Absorbed in their own complex political institutions and intensely local religion, they had no interest in governing their neighbors after defeating them. Instead, they made allies of them. The Romans would swear to protect their new allies; in return, the new allies would pledge to furnish troops when called upon.

The ancient Latins took oaths very seriously, and the Romans rapidly gained a reputation as extremely reliable allies. Writing 200 years later, the authors of the Book of Maccabees paid tribute to this Roman trait: “With their friends and those who have relied upon them, they kept friendship.”

The problem was that this very reliability continually created new security challenges. Having conquered their neighbors in order to secure their own horizon, the Romans now found themselves committed to protect their new friends against threats. New commitments drew them into new wars, led them to defeat new enemies, swear these new enemies into the alliance, only to find themselves with yet a further concentric ring of enemies.

The logic of this system eventually led the Romans to unite the entire Italian peninsula under their leadership, a task effectively complete by about 300 B.C.E. Yet this united Italy was a land of many governments, each sovereign, each with its own institutions, each with its own army.

Madden argues that Italy in the 200’s B.C.E. looked a good deal like NATO after 1950. One ally was clearly the strongest and most influential. But that strength did not rest on terror. It rested on the leading ally’s credibility. The other allies trusted the leading ally not only to defend them when defense was called for, but to use its power responsibly in the interests of all. They had built an empire not of conquest, but of trust. And it is this, Madden holds, that the United States has done as well.

The Roman system encountered its most severe test in the late 200’s B.C.E., when the Carthaginian general Hannibal invaded Italy. Hannibal was one of the great commanders of history, and his strategy against Rome was essentially the same as Alexander’s against Persia: insert an army into the territory of the enemy empire, win a battle or two, show the empire’s subjects they no longer need fear the empire’s power, and then watch the enemy empire shatter into fragments.

The strategy worked for Alexander. It failed for Hannibal. Despite inflicting defeat after defeat upon the Roman army on the territory of Italy, Hannibal could not crack the Roman alliance. Even after he sacked Italian cities in an effort to make the Italians fear him more than the Romans, the alliance held firm.

Hannibal’s difficulty was that the Italians did not fear the Romans. They trusted them — and they preferred the deal the Romans offered them not only to subordination by Hannibal and Carthage but even to the recovery of their own independence. Such a recovery would have meant returning to a condition in which each Italian city must constantly prepare for war against any and all of its neighbors. Roman rule, by contrast, meant peace and security for all.

The Romans finally turned the tide of war by doing to the Carthaginians what the Carthaginians had done to them: they landed an army on their home territories, first in Spain and finally in what is now Tunisia. The result dramatized the difference between the Roman and Carthaginian polities: when Rome won a battle against Carthage, Carthage’s allies did desert, and the Carthaginian empire disintegrated.

Yet even under these conditions, Rome did not destroy Carthage. Only after a third war a half-century later did Rome finally impose its notorious “Carthaginian peace.” (Two thousand years later, the U.S. Congress would debate how to treat Germany once World War II came to an end. One hard-line Senator was accused of seeking a “Carthaginian peace.” He answered: “Well we haven’t had much trouble from Carthage recently.”)

Now began a phenomenon Americans will recognize. Before the Carthaginian wars, the Roman state grew of its own volition. The empire “pushed” outward, in a deliberate effort to neutralize its neighbors. From the middle of the 2nd century B.C.E. onward, however, the empire was more often “pulled.” Smaller Mediterranean powers, like the Maccabean Jewish state, craved the same protection against predatory neighbors that Rome’s Italian allies enjoyed. They requested Roman alliance. If they obtained it, they soon involved Rome in their local quarrels—and eventually pulled Rome into further expansion.

Between about 290 B.C.E. and 146 B.C.E., Rome traced a history very like that of the United States from 1890 to 1990: from being the dominant power in its own “hemisphere,” it rose to become one of two rival superpowers and finally to occupy the position of dominant military force in the known world.

Throughout this transition, the Romans, like the Americans, were as likely to resist new commitments as to seek them. Soon after the second Carthaginian war, the Romans were invited into the complex power struggles of Greece. They fought a war with the king of Macedon, defeated him, announced the liberation of Greece from foreign rule, and withdrew all their forces from the peninsula.

Yet turmoil in Greece kept pulling the Romans back and back again, until they finally established a province in the same year they finished off Carthage—becoming not only the protectors of Greece but also conscientious custodians of the place’s artistic and cultural heritage.

Madden’s core observation is that security is a precious and highly desired resource, and when one society becomes strong enough to offer security on favorable terms, other polities will eagerly accept. Trustworthy security, Madden contends, is what Rome offered first to Italy and then to the entire Mediterranean world. And it is what the United States offers today.

Roman hegemony, like American power, provoked considerable grumbling. There was a vast literature of anti-Romanism in Greek just as there is a vast literature of anti-Americanism in the languages of Europe. Madden insists, however, that the test of trust is not what grumblers say. It is what they do.

Well into the 200’s of the Common Era, a third of a millennium after the salting of Carthage, the Roman empire remained a constellation of quasi-independent city-states. These states retained, as America’s present-day European allies retain, the option of paying for their own armies and casting off their ties to Rome. They did not exercise that option, and that non-exercise is what we know as the Pax Romana.

Just as the French, no matter what they say, prefer not to see even a friendly independent German military force across the border, so the Rhodians happily forswore their own navy in exchange for naval disarmament by all the other potential Mediterranean powers. The characteristic of an empire of trust is precisely that its allies trust its power more than they trust any great-power rival, more than they trust any of their neighbors, sometimes even more than they trust themselves.

The remarkable thing about such an empire is not that it eventually falls. All human societies eventually fall. The remarkable thing is that it could ever come into being in the first place. As the empire of trust establishes itself, in Madden’s telling, allies begin to demand greater rights to participate in decision-making at the center. Rome faced a shattering rebellion in the 90’s B.C.E. from its Italian allies. The allies did not demand independence. They demanded Roman citizenship. They lost the war, but gained their demand. It is very striking to recall that the emperor Augustus was the son of a non-Roman Italian father.

Citizenship was progressively extended wider and wider, until by the 200’s C.E. it was extended to all non-slaves. Long before then, the Roman Senate had been filled with landowners from across the Mediterranean world. Future emperors would come from what is now Spain, Syria, and Croatia. A city-state had evolved into a pan-Mediterranean community.

Is this the future of the American “empire of trust”? Madden is inclined to think so. He speculates about English displacing local languages as Latin displaced the native languages of what are now France, Spain, and Romania. He predicts that the European Union will never generate an effective military counterweight to the United States, that China will frighten more than it attracts, and that American hegemony will endure for a very long time.

At this point, the dictum of Roberto Lopez, suspended almost all the way through this engaging and original work, began to sound in my ears. No, history does not repeat. But it does teach—and Thomas Madden here shows himself a marvelous teacher.