Editor’s Note: This is part of a running series of essays by Iskander Rehman, entitled “Applied History,” which seeks, through the study of the history of strategy and military operations, to better illuminate contemporary defense challenges.

Wild nations are pressing upon the Roman Empire and howling about it everywhere, and treacherous barbarians, shielded by geography, are assailing every frontier. For usually the aforesaid nations are either covered by forests, occupy commanding mountain positions, or are defended by snow and ice, while some are nomadic and are protected by deserts and the burning sun. Others are defended by marshes and rivers and cannot easily be tracked down; yet they tear at our peace and quiet with their unexpected forays.

– De Rebus Bellicis, author anonymous, mid-4th century AD

On a scorching summer day in 378 AD, Rome’s Eastern Army — a formidable force composed of tens of thousands of cavalry, legionnaires, and auxiliaries — moved to crush a rebellion of Gothic refugees near Adrianople, in present-day Turkey. Led by Fritigern, a canny Visigothic chieftain and erstwhile ally of Rome, the fierce Germanic tribesmen had been granted resettlement on Roman territory after fleeing across the Danube. As often in this age of upheaval and mass migration, the patchwork coalition of marauding Goths had themselves been displaced by an even more fearsome foe, the Huns, “a race of men, hitherto unknown” to the Romans who had, in the words of one startled contemporary, “suddenly descended like a whirlwind from the lofty mountains, as if they had risen from some secret recess of the earth, ravaging and destroying everything which came in their way.” Disarmed and hideously abused by the Roman frontier units charged with their relocation, the Goths ultimately found themselves reduced to selling their own children into slavery in exchange for rancid dogmeat. Months of such inhumane treatment had eventually sparked widespread revolt, with Fritigern rapidly rallying thousands of fellow tribesmen to his banner. Already struggling to extinguish a series of bushfire revolts and incursions all across the “hewn edges” of its sprawling but increasingly battered empire, Rome painstakingly mobilized a large field army, with the aim of eradicating the Gothic threat once and for all. Led by the Emperor Valens himself, the Romans had good reason to believe they would prevail: They were seemingly numerically superior and far better equipped than the disparate grouping of barbarians encamped within their rustic wagon circle.

Instead, for a concatenation of reasons — ranging from poor intelligence analysis to heat exhaustion to Rome’s signal underestimation of Fritigern’s generalship — the day ended in disaster, with Valens losing his life along with close to two thirds of his army under dust-choked skies, on a sweltering plain “covered with corpses” and filled with “the groans of the dying.” As night crept over the charnel ground, it almost seemed, lamented the Greek court orator Themistius, that “an entire army had vanished like a shadow.” Both the 4th-century soldier Ammianus Marcellinus and the great 18th-century historian Edward Gibbon would compare the slaughter at Adrianople to that several centuries earlier at Cannae, during the darkest days of the Second Punic War, with Gibbon observing that:

A great number of brave and distinguished officers perished in the battle of Adrianople, which equaled in the actual loss, and far surpassed in the fatal consequences the misfortune which Rome had formerly sustained at Cannae.

Whether this is a characteristically Gibbonian overstatement remains a matter for debate. What is not, however, is the simple fact that a century after the carnage of Cannae, a resuscitated Rome was nearing the apex of its ascendant trajectory, whereas 100 years after the grim slaughter at Adrianople, the Western Roman Empire had dissolved into a congeries of barbarian kingdoms and statelets. It was in the midst of this troubled era — this damnatum saeculum of disorder and dislocation  — that one of history’s most influential strategic texts was written: Publius Vegetius Renatus’ Epitoma Rei Militaris, now more commonly known as De Re Militari, which literally translates as “Of Military Affairs.” It is a text that demands to be rediscovered, given its textual richness and immediate relevance to our age of instability and protracted warfare. Indeed, many will be familiar with one of Vegetius’ most famous dictums, “He who desires peace, let him prepare for war,” which — like Sun Tzu’s maxim in The Art of War “To subdue the enemy without fighting is the acme of skill” — has acquired almost a bumper sticker quality in the field of strategic studies. Beyond that, however, there is a glaring absence of Vegetius in most curriculums — an unfortunate form of historical amnesia in need of remedy.

The Most Influential Strategist You’ve Never Heard Of

There remains a good deal of uncertainty over Vegetius’ exact identity. It would appear that he was a government official of some rank, but it remains unclear which office he held. It is also uncertain whether he had frontline military experience, or whether his granular knowledge of operational issues stemmed from a more administrative set of responsibilities. With his encyclopedic knowledge of earlier Roman writers, Vegetius was clearly well versed in the classical tradition, and eager to show it. Indeed, De Re Militari purportedly began its life as a memorandum of proposals on military reforms for the emperor, before being expanded into its later form. Which emperor that was — and when exactly the full version of the treatise was compiled — has been a topic of much academic debate and antiquarian quibbling over the millennia. What we do know is that the text was written sometime between 380 and 450 AD, and most likely before the sack of Rome by the Visigothic ruler Alaric in 410 AD, as this system-shattering event is never mentioned. Curiously, Adrianople is never overtly referenced either, perhaps due to its continued political sensitivity, although there are number of damning allusions and transparent innuendos sprinkled throughout the text on the kind of failures — in tactics, intelligence, and training — that had contributed to the disaster. As one historian notes, years after its occurrence, Adrianople evidently continued to gnaw at the Roman psyche, and:

in the tactical arena, he (Vegetius) often counsels how to avoid errors that correspond to those made at Adrianople: always know the strength of enemy forces — Valens grossly underestimated; avoid employing untrained recruits — Valens enlisted new men shortly before the battle; avoid engaging in open battle when raids are possible — Valens rejected similar advice; avoid marching troops too far to battle and fighting in unfavorable conditions — Valens did both in August 378.

Most famously, Vegetius urged Rome to revert to an earlier force design, with a greater focus on well-drilled heavy infantry, and to revamp its recruitment practices, with a prioritization of native citizens over foreign troops and allies. (In this, as well as on a myriad of other issues, he would greatly inspire early modern authors such as Machiavelli). Much like his near-contemporary St. Augustine, Vegetius was preoccupied with the idea of civilizational decay and the concurrent need for moral renewal. Written in an era of perpetual conflict and internecine strife, De Re Militari is not so much a manual for heady expansion as a conservative blueprint for imperial stability and territorial preservation.

If De Re Militari was simply an atavistic plea for military reform by a querulous bureaucrat, however, it would hold little interest for anyone beyond the shrinking groves of late Romanist academia. Instead, there is a reason why generations of military professionals, from the Middle Ages to the Napoleonic Age, and from John of Salisbury to Frederick the Great, held Vegetius’ intellectualized approach to warfare in deep reverence. Indeed, as one classicist pointedly asks, what other book on military affairs was as prized in the Age of Enlightenment as De Re Militari had been by the Venerable Bede? In many ways, Vegetius would prove as influential in the domain of military strategy as St. Augustine in the fields of philosophy and theology. It can be argued that his writings are no less pertinent today, especially in light of the war in Ukraine and the revival of great-power competition. This is for three main reasons.

First, Vegetius can help us think in terms of campaigns rather than individual battles, while reminding us of the importance of planning and intelligence as a means of preemptively shaping the battlefield. Second, he provides a sophisticated understanding of the close articulation between strategies of attrition and annihilation, at a time when both forms of warfare are all too often viewed in artificially dichotomous terms. And last but not least, he places a welcome emphasis on the fundamental importance of discipline, training, and morale when waging a protracted war.

Shaping the Battlespace and Preparing for Protraction

For much of Vegetius’ life, the Roman Empire was under severe and continuous pressure — both from without and within. Within, the empire was subject to increasingly debilitating fissiparous pressures as the imperial succession gradually devolved from what had once been a relatively orderly process into competing, and increasingly chaotic, forms of warlordism. Meanwhile, across the fortified belt of fortlets and watchtowers that separated the Roman world from the thick forests, craggy peaks, and rushing rivers of the barbaricum, Rome’s beleaguered garrisons struggled to fend off bands of whooping raiders and winding wagon trains of desperate migrants. When facing especially dire circumstances, these frontier forces, or limitanei, could call for assistance, with the hope that one of Rome’s mobile field armies, the comitatenses, would eventually come to their aid. In many cases, however, these expeditionary forces could take months to mobilize the requisite manpower and materiel and then arrive in theater. The ability for Rome’s often outnumbered and isolated forward-deployed forces to both husband scant resources and deny or delay enemy action was thus critical.

And indeed the importance of time — as a resource to be managed and a currency to be spent — is central to the Vegetian approach to strategy. So is the necessity to engage in proper planning and to think iteratively in terms of campaigns rather than individual engagements. As the medievalist Christopher Allmand rightly notes, if one idea dominates much of Vegetius’ work, it is “forethought,” i.e. “the military virtue of anticipation.” Thus, notes Allmand:

the successful commander looks further ahead than does the enemy: he foresees difficulties of all kinds, and he leads a well-disciplined and versatile army, prepared by its training for every eventuality, to gain both a moral and practical advantage over the enemy. Above all, the successful leader is ever-ready to seize any opportunity to harry, hinder, discomfort, or wrong-foot the enemy, thereby dissuading him from seeking a major encounter which can, as Vegetius admits, go wrong.

The risks of overly focusing on the concept of decisive battle is indeed a leitmotif of Vegetius’ work — and for several reasons.

First, in a world of finite military resources, large set-piece battles were high-risk endeavors, subject to the cruel whims of “fortuna” and rife with all manner of potential hazards. Vegetius fully recognized the heroic allure of climactic engagements, even anticipating his readers’ frustration when he advocates for a more cautious and methodical approach to campaigning:

Readers of this military treatise will perhaps be impatient for instructions relative to general engagements. But they should consider that a battle is commonly decided in two or three hours, after which no further hopes are left for a worsted army. Every plan, therefore, is to be considered, every expedient tried and every method taken before matters are brought to this last extremity. Good officers decline general engagements where the danger is common, and prefer the employment of stratagem and finesse to destroy the enemy as much as possible in detail and intimidate them without exposing our own forces.

At a later point in the treatise, Vegetius belabors this point even further, noting that any large-scale general engagement was a “conjuncture full of uncertainty” and potentially “fatal to kingdoms and nations, for in the decision of a pitched battle consists the fullness of victory.”

Second, a strategy of delay and protraction could, in some instances, play to Roman armies’ inbuilt advantages in terms of logistics and long-term mobilization. With the exception of its sole peer competitor, Sasanian Persia, Rome’s barbarian foes largely consisted of temporarily raised levies of farmers or herders, with usually only a small core of professionalized standing forces. Therefore, Vegetius coldly observes, it was often to Rome’s advantage to play a waiting game, with the hope that its adversaries, suffering from moral exhaustion and growing socio-economic pressures, would eventually collapse of their own accord:

The enemy sometimes operate under the expectation that their expedition will soon be over; and if it ends up lasting longer (than expected), their troops are either consumed by want and lack of supplies, desperate to return home to be with their families, or, having achieved nothing of note in the field, end up dispersing from despair of success. Many of them, exhausted and discouraged, will desert, whereas others will either switch allegiance or surrender. … And thus, in such cases an army which was numerous at the beginning of hostilities gradually dwindles away into nothing.

And finally, an inordinate focus on climactic, set-piece battles could cloud a commander’s judgment, preventing him from thinking creatively and iteratively about future contingencies. Much like Carl von Clausewitz, Vegetius sought to continuously remind his readers of the fundamentally interactive nature of conflict. A full millennium and a half before the Prussian military theorist described war as “a continuous interaction of opposites” and “the shock of two hostile bodies in collision,” Vegetius had laconically observed that:

It is the nature of war that what is beneficial to you is detrimental to the enemy and what is of service to him always hurts you. Its therefore a maxim never to do, or to omit doing, anything as a consequence of his actions, but to consult invariably your own interest only. And you depart from this interest, whenever you imitate such measures as he pursues for his benefit. For the same reason it would be wrong for him to follow such steps as you take for your advantage.

Thus, if one’s adversary was hankering for frontal collision and for a prompt, high-intensity engagement, they might have good reason to do so, and it might therefore make sense to adopt a strategy of exhaustion and battle avoidance — and vice versa. More broadly, the sound execution of strategy, De Re Militari repeatedly suggests, demands a certain inherent plasticity of mind, most notably the ability to think across multiple time horizons and well beyond the first clash of arms. To give one contemporary analogy, in the world of finance analysts distinguish between forecasting, which is employed for near-term predictions, and projections, which estimate financial results further into the future. Military strategy, Vegetius reminds us, is no different. Thus, he notes, “even the most unskillful” military commanders consider the terrain and meteorological conditions when arranging their troops for battle. How many, though, are prudent enough to “extend their views beyond the present” and “to take such measures as to not be incommoded over the course of the day by shifting aspects of the sun or by contrary winds which often rise at a certain hour and might be detrimental to (their action)”? This practical exemplum could easily serve as an illustrative metaphor for the entire book, which constantly warns us that — much like an initially translucent sky on a blustery fall afternoon — military fortunes can suddenly and unexpectedly darken over the course of an extended campaign.

How then, could the aspiring Roman officer best plan for the fog and friction of war, all while learning how to better connect short-lived individual military actions to more drawn-out campaign strategies? Through regular training, sound logistical planning, and exquisite intelligence work, posits Vegetius — in essence what we might today describe as “shaping” the operational environment. Much as contemporary defense planners fret about the state of missile inventories and fuel depots in the Indo-Pacific theater, Vegetius repeatedly prods his fellow Roman officials to rigorously account for forage, munitions, and materiel stockpiles and to ensure that they are well prepositioned in theater, for “when provisions begin to fail, parsimony is ill-timed and comes too late.”

Roman intelligence agents should be “constantly abroad” “tampering with their (the enemy’s) troops and encouraging deserters.” By these means, the Roman official notes, Rome could be fed a steady stream of “intelligence on their present and future designs” and “get to know thoroughly” the operational “habits of the enemy.” Once this carefully curated intelligence had arrived on the general’s desk, he was able to engage in the next step of the planning process. Importantly, this should never be done alone, but always in close consultation with his military staff over the exact nature of the threat and which direction to pursue. What should follow, Vegetius argues, sounds not too dissimilar to a contemporary net assessment, a clinical, dispassionate process he compares at one point to that of a “civil magistrate weighing between two parties.” Thus, he notes:

It is the duty and the interest of the general to frequently assemble the most prudent and experienced officers of the different corps of the army and consult with them on the state both of his own and the enemy’s forces. All overconfidence, as most pernicious in its consequences, must be banished from the deliberations. He must examine which has the superiority in numbers, whether his or the adversary’s troops are best armed, which are in the best condition, best disciplined and most resolute in emergencies.

In addition to engaging in a detailed survey of the local geography, climate, and terrain, one of the most important additional evaluations was that of the enemy’s resource base and ability to sustain a continuous tempo of high-intensity operations. For, adds the Roman official, “plenty and scarcity in either army are considerations of no small importance” and “famine, according to the common proverb, is an internal enemy that makes more havoc than the sword.”

Only then, once a clear picture of the enemy’s military strength and resiliency had been drawn, was it time to take the final, most fateful decision — i.e., to “determine whether it is most proper to temporize or to bring the affair to a speedy decision by action.” And it is here, when he fully grapples with this perennial intellectual challenge in times of protracted war — dissecting the tight interrelationship and complex sequencing between strategies of attrition and annihilation — that Vegetius can no doubt prove the most useful to contemporary defense planners.

Between Attrition and Annihilation

For decades, there has been a noted tendency among Western defense analysts and military professionals to clearly distinguish between strategies of attrition and annihilation, with many establishing something of an artificial dichotomy between the two. Famously, in the 1970s, the military historian Russell Weigley argued in his classic The American Way of War that the United States had become overly wedded, due to its “wealth and adoption of unlimited aims in war,” to strategies of annihilation, i.e., what he and others portrayed as heavily maneuverist strategies that sought, first and foremost, to rapidly overthrow or dislocate the adversary. And while Weigley personally regretted this excessive focus on annihilation, many others deemed it preferable to attrition, or strategies of exhaustion, which were often perceived as “unheroic”, “dehumanized” forms of warfare born principally out of moral or material weakness. And indeed, from its semantic beginnings in Catholic doctrine (which characterizes “attrition” as an insincere, and therefore imperfect, form of contrition), the term has come draped with negative interpretations. Stemming from the Latin atterere, meaning to “rub against” or “grind down,” attritional warfare became associated in the popular imagination with the dank trenches and mass bloodletting of World War I and thus, notes the historian Hew Strachan, became endowed with connotations of needless “slaughter and waste,” even though, of course, this would be a hugely simplistic reading of the strategies pursued by the conflict’s warring parties.

Part of the problem, no doubt, lies in the definitional slipperiness of the term. Is attrition a “destruction-centered” approach, as some have argued, or is it one that places more of an emphasis on Fabian strategies of battle avoidance and harassment? Is it solely material, or can it also be virtual, i.e., by employing clever tactics that cause the adversary to redirect its forces or, more broadly, “adjust its behavior in ways that decrease the quality, amount, of rate of combat power brought to bear”? Finally, does it seek, first and foremost, to take aim at an enemy’s military capacity, industrial resiliency, will to fight, or at all of the above? Perhaps one of the most succinct and workable definitions is provided by Antulio Echevarria, who remarks that:

Attrition is perhaps the most straightforward of military strategies. In its simplest form it means destroying an opponent’s forces faster than they can be replaced, while at the same time ensuring one’s own rate of loss remains bearable.

Beyond its deceptive simplicity, however, Vegetius provides us with a salutary reminder of attrition’s manifold varieties beyond simple kinetic destruction. His heavy emphasis on slow-burning strategies of starvation — with his famous adage that “to distress the enemy more by famine than the sword is a mark of consummate skill” — might have, until relatively recently, seemed outdated to 21st-century defense analysts. Since the war-induced famine in Tigray, however, or the horrific siege of Mariupol in 2022, when Russian forces ruthlessly and systematically targeted the Ukrainian defenders’ energy, water, and food distribution points, the late Roman official’s observations no longer seem quite so quaint. Vegetius also places much emphasis on the use of climate, terrain, and deception as a means of whittling away at enemy troops and morale, always with the hope of fomenting lasting disillusion and fatal discord, for “no nation, though ever so weak in it itself can be completely ruined by its enemies unless its fall be facilitated by its own distraction.” Once again, he emphasizes the importance of robust reconnaissance work, urging Roman officers to time their “ambuscades” when the enemy is fatigued after a long march or “taking their refreshments or sleeping, or at a time when they suspect no dangers and are dispersed, unarmed and their horses unsaddled.” Parties should also be detached to target pre-identified enemy forage and munition depots, for “scarcity of provisions, which is to be carefully guarded against in all expeditions, soon ruins such large armies where the consumption is so prodigious, that notwithstanding the greatest care in filling the magazines they must begin to fail in a short time.”

In addition to emphasizing attrition’s protean nature, Vegetius can help us better understand the fallacy of seeking to clearly differentiate or “rank” strategies of annihilation versus attrition. Much like two later and oft-cited but seldom read theorists of attrition, the German historian Hans Delbrück and the Soviet writer Alexander Svechin, Vegetius’ thought has often been overly simplified. Particularly among medievalists, the adjective “Vegetian” has almost automatically become equated with strategies of exhaustion and attrition. However, as the West Point professor Clifford Rogers has rightly noted, this greatly overstates the degree of the Roman author’s battle-avoidance. Indeed, for the latter, the choice of attrition over annihilation was largely circumstance-dependent — all of the knottiest decisions in war were intricately tied to questions of timing and opportunity. Certainly, it made sense, if a general needed to buy time or “knew himself to be inferior,” to “avoid general actions and endeavor to succeed by surprises, ambuscades and stratagems,” which “when skillfully managed … have often given … victory over enemies superior both in numbers and strength.” But if he found himself “in many respects superior to his adversary” then, Vegetius asseverates, he “must by no means defer bringing on an engagement.”

Much like Svechin, who wrote that “a strong and sudden transition from defense to offense, a shining riposte” constituted the “highest achievement of military art,” Vegetius remarks that the decision to engage in large-scale general actions or decisive battle was the “eventuality” that “above all others requires the exertion of all the abilities of a general … This is the moment in which his talents, skill and experience show themselves in their fullest extent.” There was thus a time and place for attrition, a time and place for annihilation, a time and place for entrenchment, a time and a place for maneuver, a time and place for artful shadowboxing, and a time and a place for brutish collision. The supreme art of generalship consisted in accurately diagnosing the exact moment “opportunity offers,” i.e., when that momentous change in techniques, tactics, and procedures was most urgently required. The Ancient Greeks had a specific word for this: kairos, a term distinct from the more familiar chronos and which, by characterizing that precious and elusive sense of propitiousness — either in war, athletics, or rhetoric — marked the quality of a moment in time rather than its quantity.

Correctly identifying that “kairotic moment” and deciding to transition from a strategy of attrition to one of annihilation has always been a risk-laden decision, and therefore frequently controversial. In the final years of the Second Punic War, Gen. Quintus Fabius Maximus Cunctator (the Delayer) wished to perpetuate the strategy of exhaustion that had allowed Rome to survive during the darkest hours of the Hannibalic War, after its terrible defeats in the battles of Trebia, Trasimene, and Cannae. For Fabius, as long as Hannibal and his armies remained in Italy it made sense to concentrate the bulk of Roman military asserts and resources close to Rome, where they could engage in homeland defense, targeting Hannibal’s allies and supply lines and patiently whittling away at the invaders’ foraging parties and new-found Italian allies. For the younger Publius Cornelius Scipio (later known as Scipio Africanus), on the other hand, the only means to bring the war to a close was to transfer its costs onto enemy territory by invading North Africa and directly threatening the very nucleus of Carthaginian power, thus luring Hannibal, its most capable commander, back to his home shores. He preferred, he stated somewhat provocatively, to “devastate the territories of another” rather than witness his own “destroyed by fire and sword,” and to “draw Hannibal after him” rather than be “kept here [in Italy] by him.” Scipio’s audacious gambit ultimately proved more successful than the more defensive, attritional approach still espoused by Fabius, leading to the recall and eventual defeat of Hannibal and the surrender of Carthage.

Similarly, in 1918, Gen. Philippe Petain and Gen. Ferdinand Foch found themselves in deep disagreement over the direction of French and allied military strategy. Whereas Petain, alarmed by the early successes of the German spring offensive (and perhaps foreshadowing his loss of nerve during World War II), argued in favor of abandoning Paris and withdrawing deeper into France’s interior, Foch boldly asserted that Gen. Erich Ludendorff’s offensive was nearing its point of culmination and advocated in favor of a vigorous French-led counter-offensive. Following the Allied victory at the Second Battle of the Marne, a triumphant Foch observed in a memorandum to his fellow allied commanders that the allied armies had arrived at a “turning point of the road” and that it was now time to relaunch a war of initiative and movement, writing, “The moment has come to abandon the general defensive attitude forced upon us until now by numerical inferiority and to pass to the offensive.”

Both Foch and Scipio were duly vindicated in their respective assessments of the military situation. In each case, this was not due to the inherent superiority of one rigidly defined “form” or “category” of warfare over another, but rather to the generals’ sense of kairos in the midst of a rapidly evolving and newly fluid combat environment. More broadly, this was also a question of sequencing — neither 3rd-century BC Rome nor early 20th-century AD France could have survived to launch their successful counteroffensives absent their initial adoption of more attritional strategies.

Training, Discipline, and Morale in Protracted War

War, Clausewitz memorably observed, is often “saturated by great moral forces” that leave it “with a leaven of its own.” A protracted great-power war is above all an extended clash of national wills, and the preservation of civilian and military morale, even in the face of severe loss and deprivation, ought to be at the heart of any viable theory of victory. Time and time again in De Re Militari, Vegetius insists on the importance of strict training regimens and routinized military exercises as a precious source of Roman comparative advantage. This, in and of itself, was hardly novel — as far back as the 1st century AD, a number of both Roman and foreign observers had argued that it was the fighting cohesion and discipline of the legions that lay at the heart of their success and distinguished them from the unruly hordes of their adversaries. Flavius Josephus, an aristocratic Jewish priest who had witnessed the Roman legions in action against his own countrymen during the revolt of Galilee in 66 AD, had thus famously quipped that, “it would not be far from the truth to call their drills bloodless battles, and their battles bloody drills.”

Writing at a time of acute manpower shortages, marked by widespread desertion and a chronic recruitment crisis — and with conscripts frequently engaging in acts of self-mutilation to skirt military service — Vegetius was desperate to renew with this hallowed Roman tradition. “Few men are born brave,” he drily opines, “but many more become so through care and force of discipline.” Vegetius’ uniqueness lies in the degree to which he frames training not only as a means of perfecting a unit’s technical warfighting skills but also as indispensable to the preservation of morale during a protracted campaign. Thus, continuous training lends the man deployed far from hearth and home structure and purpose, psychologically acclimatizing him to both the grinding tedium of extended garrison duties and the inherent unpredictability of life along a savage frontier. “The difference is great,” Vegetius avers, “whether your troops are raw or veterans, whether inured to war by recent service or for some years unemployed.” He then warns of the dire consequences of even temporarily interrupting a training cycle, for “soldiers unused to fighting for a length of time must be considered in the same light as recruits.” The granite-faced Romans of yesteryear, he nostalgically sighed:

thoroughly understood the importance of hardening them (the levies) by continual practice, and of training them to every maneuver in the line and in action. Nor were they less strict in punishing idleness and sloth. The courage of a soldier is heightened by his knowledge of the profession, and he only wants an opportunity to execute what he is convinced he has been perfectly taught. A handful of men, inured to war, proceed to certain victory, while on the contrary numerous armies of raw and undisciplined troops are but multitudes of men dragged to slaughter.

Barring perhaps Xenophon, no other classical author spends quite as much time focusing on the psychological dimensions of leadership — indeed, the ideal Vegetian officer is both a flinty patriot and a shrewd judge of character, with an almost preternaturally intuitive reading of his grunts’ morale. “Men,” Vegetius offhandedly remarks, are “frightened and thrown into disorder by sudden accidents and surprises” that would otherwise be of little consequence if correctly foreseen. Diligent drilling constitutes one form of curative against such precipitous collapses in morale, and regular “blooding” provides another, for “the objects with which we are once familiarized are no longer capable of inspiring us with terror.” Indeed, De Re Militari bluntly states that one of the advantages inherent to protracted guerilla campaigns and wars of harassment is that they provide a steady stream of opportunities for raw troops to be hardened “through frequent skirmishes and slight encounters.” Ideally, Vegetius observes, a commander should:

continue these kinds of encounters until his soldiers have imbibed a proper confidence in themselves. For troops that have never been in action or have not for some time been used to such spectacles, are greatly shocked at the sight of the wounded and dying; and the impressions of fear they receive dispose them rather to fly than fight.

A general’s psychological discernment should also extend, De Re Militari repeatedly stresses, to the examination of enemy morale. Famously, he observed — reprising Scipio’s well-known maxim that “a golden bridge” should be made for a fleeing enemy — that there were few things more dangerous than a cornered enemy with nothing left to lose, and that:

in such a situation, where no hopes remain, fear itself will arm an enemy and despair inspires courage. When men find they must inevitably perish, they willingly resolve to die with their comrades and with their arms in hands.

Vegetius is at his most penetrating, however, when he comments on how best to bolster morale after a temporary setback or defeat — urging Roman officers in such circumstances to remind their despondent troops that one lost battle does not a lost war make. This is where historical perspective can be the most useful, the military theorist suggests, for even in such extremities “the constancy and resolution of a general may recover a complete victory” and “there are innumerable instances where the party that gave least way to despair was eventually esteemed the conqueror.” Ever the steadfast voluntarist, Vegetius concludes the general body of his treatise with the following historically minded reminder of the perils of trying to prematurely predict the outcome of a protracted war:

If anyone should imagine no resource is left after the loss of battle, let him reflect on what has happened in similar cases and he will find that they who were victorious in the end were often unsuccessful in the beginning.

A Strategist for Our Times?

For all his steely optimism, Vegetius was ultimately to prove unsuccessful in his mission to reform Rome’s legions, restore its sinking sense of purpose, and revive its moribund empire. Indeed, little could he have known that he would be more heeded by generations of his successors — from armor-clad crusaders to brocade-festooned Napoleonic generals — than by his embattled contemporaries. Today his writings have sadly fallen into abeyance — and yet, as we have seen, so much in our troubled present seems to call for a general rediscovery of his work.

Consider, for example, the brutal war in Ukraine, which has now raged for close to three years and has already gone through several distinct phases that Vegetius, as an able anatomist of protracted warfare, would have immediately recognized. It is a war that has begun, as one excellent recent study notes, to “align with historic patterns of large-scale conventional wars,” cycling through “prolonged periods of positional fighting, offensives and counteroffensives, sieges in urban terrain, phases dominated by high levels of attrition, and operations to break through a prepared defense.” The rancorous discussions over when to time said counteroffensives, whether to open new fronts (either in the Kursk Oblast or occupied Crimea), when to hoard and when to expend finite artillery shells, when to advance and when to stage a fighting retreat — these are all kairotic questions at the heart of De Re Militari. Ukraine’s tortuous internal debates over the extent and duration of mobilization and frontline service are reminiscent of Vegetius’ commentary on the challenges of balancing effective training and accelerated, large-scale recruitment in long wars. And, once again, we are reminded of the priority to be attached to morale preservation in conflicts where the passage of time can have an erosive quality in and of itself. Meanwhile, the Vegetian emphasis on logistics, lines of communication, stockpiling, and reconnaissance appears equally — indeed almost eerily — relevant to contemporary debates over U.S. military resilience and readiness in the Indo-Pacific theater. Perhaps, then, it is time to resurrect De Re Militari from the dusty intellectual catacombs to which it has been relegated, and bring its author’s world-weary wisdom back into the light.

At one point in the midst of his treatise, Vegetius suddenly breaks the fourth wall, admonishing his readers for their presentism and lack of interest in military history:

Are we afraid of not being able to learn from others? … At present all this to be found in books only, although formerly constantly practiced. Inquiries are now no longer made about customs that have been so long neglected, because in times of peace, war is looked upon as an object too distant to merit consideration. … In former ages, the art of war, so often neglected and then forgotten, was as often recovered from books and reestablished by the authority and attention of our generals.

He may have been scolding his complacent fellow Romans but, in truth, he could just as easily have been addressing us.

Iskander Rehman is a senior political scientist at the RAND Corporation. He can be followed on twitter at @IskanderRehman.

Image: A reproduction of a battle between Roman soldiers and Dacians, accessed via Wikimedia Commons