How does one fight a war for a buffer state?

A war for the maintenance or reestablishment of a buffer state is a peculiar beast. It is not a war of conquest, because direct territorial control would undermine the purpose of the buffer. It is also not a war aiming to inflict a massive defeat on the rival power, due to the recognition that such an outcome would be undesirable and unfeasible (hence, it is better to be separated). The objective is to bring back a zone of separation, lowering the tensions between the rivals and allowing for an economy of force in that region.

The war for Ukraine is a case in point. A geopolitically independent, economically stable, and militarily confident Ukraine would separate a revanchist Russia from the West, establishing a buffer of sorts. It would also allow Europe and the United States to enjoy an economy of force in the region, continuing the security posture of the past decades characterized by anemic defense expenditures, limited and decreasing presence of American military might in the region, and the freedom to focus on other regions or issues.

For those in the West who are willing to restore the status quo ante in Ukraine and in the wider region, the initial question—how does one compete for the restoration of a buffer?—is pertinent.

A small episode in Roman history can provide some guidelines. As we now have Ukraine and Russia, Rome had Armenia and Parthia.

Parthia was Rome’s rival in Asia. But Rome had a relatively thin military presence in the region and no troops in Armenia. Preoccupied with its vast empire and lengthy frontiers, Romans seemed to have been counting on Armenia’s desire to maintain its own independence and a corresponding willingness to put up a fight in case of Parthian advances. They also hoped that Parthia, weakened by internal strife, would be reluctant to expand its influence too close to the Roman Empire, thus escalating tensions and risking a war. Armenia served as a buffer state, under neither Parthian nor Roman direct control, independent enough to care for its own autonomy and yet dependent on the adjacent great powers’ will to maintain stability.

The metric of success for the Armenian buffer was obviously the absence of a war between the rival great powers. But for Rome one crucial metric of success was also its ability to leave Anatolia and Syria relatively undefended, with most of the legions deployed along more restless frontiers such as the Rhine and Danube. For the buffer to fulfill this role, Rome had to ensure that Armenia would not fall under the control of Parthia, whose forces were much closer. The way to achieve this was to ensure that the ruler of Armenia was friendly to Rome. Thus was balance maintained: Rome had an ally in the buffer state’s leader, Parthia its forces on the buffer state’s border. By intervening in Armenia in 58 AD and replacing a pro-Roman leader with one more servile to Parthia, the Parthian Arsacids altered this delicate arrangement.

This relatively small Parthian move, and the resulting change in the internal political posture of Armenia, led to the one foreign war of great importance under Emperor Nero, from 58 to 63 AD. The historian Tacitus described the war at length in the Annales, perhaps eager to cover a subject other than Messalina’s sexual perversion or Nero’s perseverance in committing matricide.

Nero could have let Parthia’s limited intervention slide. He had plenty of nasty courtly affairs to occupy his mind and a cornucopia of amusements to satisfy his perversions. Moreover, Armenia was a distant and poor place that the vast majority of Romans did not value very much. Parthia also had internal political problems and was relatively weak, and thus did not seem inclined to continue its westward march past Armenia. Finally, war was risky for many reasons, including the possibility—dreaded by many emperors—of a victorious general returning home surrounded by his soldiers and becoming capax imperii.

Neither Rome nor Parthia appeared eager for a direct confrontation over the internal arrangements of a third country. Parthia’s little intervention in Armenia could easily have been interpreted as a silly little annoyance of no real consequence, one that did not merit Rome’s attention and resources. Yes, Rome lost a friendly ruler in Armenia, but there had been no Roman military losses and the imperial territory had not been attacked.

Nero had a choice: an uncertain war or a dishonorable peace (“bellum anceps an pax inhonesta”) (Tacitus, Annales, XV:25). The Emperor, in perhaps his best foreign policy (or policy in general) decision, chose war. And in a corollary decision, also of great luck if not wisdom, he picked a capable and experienced general, Gnaeus Domitius Corbulo, to lead the conflict.

The war over Armenia was that peculiar type of a war for a buffer zone, requiring great martial and political skills. It was a war to restore stability, not to attain supremacy; to rebuild one’s own credibility rather than to destroy the rival; to restore an independent buffer, not to conquer new lands. But it was a great power confrontation nonetheless, with all of the associated dangers of massive devastation and systemic disorder.

Corbulo’s immediate objective was the restoration of a Roman friend as Armenia’s ruler. But the the larger purpose of his military response to Parthia was to decrease Rome’s costs of maintaining security on the Asian frontier by ensuring geopolitical autonomy for Armenia. He had to fight a war for a buffer zone; a war for Roman reputation and regional stability.

The war for the Armenian buffer had one main goal: to restore Rome’s image.

In a strategic interaction over a buffer, reputation matters, perhaps even more than in large-scale direct confrontation. The existence of a buffer state is contingent on a set of often unspoken and unwritten rules that are respected because one side fears the other. Neither great power has a military presence in the buffer. But over this state there is an aura of great power interest—the expectation that the great powers separated by it will fight for its independence. When that expectation weakens for whatever reason, one of the great powers senses an opportunity to expand toward the buffer.

Another way to put this is that a buffer state is protected by a form of extended deterrence—in its simplest formulation, this is a great power’s promise to protect its allies—but without the material commitments that usually accompany it. There are no bases in the buffer, no troops rotating in and out. The buffer is defended by the image of might projected by the interested great powers, not by the actual forces they field in and around it.

Romans knew this well. Appearance—species­—was crucial in their conduct of foreign policy. An appearance of power was preferable because it allowed economy of force: The actual use of force was then unnecessary. An image of power prevented the clash of armies, and it allowed a state, Rome in this case, to have its armies dispersed and mobile rather than fixed in a place to guarantee the stability of deterrence. This is how Rome maintained security along a frontier, the length of which could not be constantly patrolled. As Tacitus puts it, the frontier potentates—among them, Armenia—relied on Rome: “Iberian, Albanian, and other kings, to whom our greatness was a protection against any foreign power” (qui magnitudine nostra proteguntur adversum extema imperia) (Tacitus, Annales, IV, 5). Not Roman legions, but Rome’s greatness!

One can note the preoccupation with appearances even in the way Romans built a simple wall girding a city exposed to the threat of roving enemies. For example, the wall protecting the Roman outpost of Tridentum (today’s Trento) on the Adige River had, from the inside of the city, a solid but not particularly orderly appearance. On the outside, however, it was perfectly laid out, with regular stones. A barbarian tribe that might have reached the city could not but have been impressed by the evident care in which the façade of the wall had been built. And first impressions mattered. The orderly exterior of the wall may not have been sufficient by itself to deter the enemy, but it was one of the many ways in which Rome built its posture of deterrence. What you show the enemy from without is different from what you see from within.

In the case of Nero and Armenia, the actual military operations were less important than the image that Rome managed to convey. A historian notes that “Public demonstrations and propaganda play a crucial role in foreign affairs, particularly when major powers are in conflict over such a token prize as Armenia and must both retain prestige.”¹

In Rome, the immediate preoccupation of shrewd imperial advisors was to show a unified court. When an embassy of Armenians came to Rome, two of Nero’s counselors (Seneca was one of them, a great Stoic philosopher but also an imperial bootlicker) carefully managed the public behavior of the Emperor and of his conniving mother Agrippina. As Cassius Dio recounts, all this was done “so that the weakness in the empire should not become apparent to the foreigners” (Cassius Dio, Roman History, LXI 3.4). A Rome that appeared divided conveyed feebleness and indecision, and as a result was less apt to sustain the image of power needed to reestablish stability in that distant region.

Related to the necessity of rebuilding Rome’s reputation was Nero’s decision to appoint Corbulo as the general in charge. Of a senatorial family, Corbulo had experienced frontier wars along the Rhine, clearly demonstrating his possession of indispensable martial talents. The selection of a good general was important not because he was capable of wielding a sword but because his reputation and his high rank would demonstrate to the enemy the seriousness of the Empire. In Tacitus’s words: “The highest rank chiefly worked through its prestige and its counsels more than by the sword and hand. The emperor would give a plain proof whether he was advised by good or bad friends by putting aside all jealousy and selecting some eminent general, rather than by promoting out of favouritism, a rich man backed up by interest” (Tacitus, Annales, XIII, 6). For at least a brief moment, Nero put merit above sycophancy.

Corbulo marched speedily to the region, “with a view to the prestige which in a new enterprise is supremely powerful” (Tacitus, Annales, XIII, 8). Speed was accompanied by tailored violence. The purpose was not to destroy Armenia, and even less so to start a large war with Parthia; rather, it was to remove Parthian influence from the buffer state.

Another general, Lucius Caesennius Paetus, had a different vision of what Rome should do. Jealous of Corbulo’s successes, Paetus criticized the apparently cautious military operations. He argued “that there had been no bloodshed or spoil, that the sieges of cities were sieges only in name.” Instead, he suggested a war of conquest: he, Paetus, “would soon impose on the conquered tribute and laws and Roman administration, instead of the empty shadow of a king.” (Tacitus, Annales, XV, 6) A few years later, in 62 AD, he was put in charge of Armenia after Corbulo’s successful military operation, only to promptly lose it again—and forcing Corbulo to return to clean up the mess. Paetus thought only in categories of conquest, not of Roman security and regional stability.

Corbulo, by contrast, mixed threats and suggestions, terror and moderation (simul consilio terrorem adicere) (Tacitus, Annales, XV, 27). One piece of advice, for instance, he directed toward the Armenian rulers who had accepted Parthian control. Surely, Corbulo told them, they did not want to rule over a wrecked polity, or sit in the middle of a great power war. Above all, they should doubt Parthian staying power. Instead, they should accept the Armenian kingdom as a gift of the Roman emperor, acknowledging Rome’s reputation of power.

He backed his advice with terror. In an episode recounted not by Tacitus but by Frontinus, when an Armenian town was stubbornly refusing to surrender, Corbulo executed “one of the [Armenian] nobles he had captured, shot his head out of a balista, and sent it flying within the fortifications of the enemy. It happened to fall in the midst of a council which the barbarians were holding at that very moment, and the sight of it (as though it were some portent) so filled them with consternation that they made haste to surrender” (Frontinus, Stratagems, Book 2, IX). Perhaps the story is apocryphal, but it conveys the decisiveness, speed, and violence used by Corbulo to restore Rome’s reputation for overwhelming power.

The target—or rather, the audience—of Corbulo’s operations was not just Parthia. In fact, the Parthian audience was secondary. Rome needed to rebuild its image first and foremost in the eyes of Armenia as well as of its own allies and clients along the eastern frontier. Armenia needed to be convinced that its pro-Parthian tilt (encouraged by Parthia’s intervention) was not sustainable, even if tempting. As Tacitus writes, “the Armenians in the fluctuations of their allegiance sought the armed protection of both empires, though by their country’s position, by resemblance of manners, and by the ties of intermarriage, they were more connected with the Parthians, to whose subjection, in their ignorance of freedom, they rather inclined.” (Tacitus, Annales, XIII, 34)

But the other allies and friends of Rome in the region also had to be shown that Roman power and reputation remained firm. At the sight of Parthian advances in Armenia some probably tergiversated, uncertain about the future and hedging their bets. The more certainty Rome could instill, the more likely they would stand by the Roman legions and defend the empire. And early on Tacitus notes that Corbulo, by his imposing eloquence, his nobility, and his speed, impressed the various allies whose sympathies then leaned toward him (studia eorum in Corbulonem promptiora ) (Tacitus, Annales, XIII, 8).

This specific conflict over Armenia ended not with a decisive victory, but with a new diplomatic arrangement, made possible and sustained by Corbulo’s operations in Armenia. The so-called “Neronian compromise” allowed the Armenian king to be Parthian but required that he be given the authority to rule by the Roman emperor. For some this amounted to a loss of Armenia: “Nero, the vilest imperator the Roman state has endured, lost Armenia”, a minor historian wrote three centuries later (Festus, Breviarium, 20). But such an evaluation was wrong. Armenia was not Roman, even though Rome wanted to have some say in the internal politics of that kingdom. The most relevant feature of Armenia was that it was a geopolitically independent state before Parthia’s intervention in 58 AD. After 63 AD it returned to that status.

As they did before this small confrontation, so afterwards Rome and Parthia continued to clash. Reaching a settlement over Armenia did not resolve the natural competition between these two great powers. But the tensions could be reduced by limiting the ability of the rivals, and in particular of the one with imperial aspirations in the region, to expand by maintaining a stable and independent state in between them.

And the maintenance of that zone of separation was predicated on the reputation—the appearance of power—that Rome could generate.

We will be wise to remember this now too. Our reputation has been weakened by Russia’s intervention in Ukraine. To let it slide, hoping to cut costs now, will force us to expend more resources later. A reputation of greatness allows for an economy of force; a weakened reputation is costly.