The Romans built one of the ancient world's largest empires, stretching from Spain eastward into the Middle East abutting Persia, and running from the provinces of North Africa to the forests of Germany and northern Britain. This empire was built on the backs of massive armies. During Hannibal's invasion of Italy during the Second Punic War, the Romans lost tens of thousands of soldiers at the battles of Cannae and Lake Trasimene, respectively, and yet continued to field large armies. Caesar took over 100,000 men with him during his invasion of Gaul. At the battle of Philippi, a Roman vs. Roman affair, both Octavian and Pompey brought armies of nearly 100,000 soldiers to the field of battle. The Consul Crassus led a failed invasion of Parthia that ended with the destruction of his army, a force numbering nearly 50,000 men. Even during the early imperial period, Trajan led armies upward of 150,000 men into Dacia.
If the empire was built by massed legions, however, it was sustained and defended by much smaller forces. During the late imperial period, the Romans suffered a disastrous defeat at Adrianople; their total force numbered between 20,000-30,000 men. The empire's massive borders were porous, and maintaining them required speed, agility, and flexibility, not the sheer volume of men that formed earlier armies of conquest. Germanic and other tribes could coalesce into large bodies of armed soldiers, but Rome's borders faced more threats from smaller raiding parties, local tribesmen living near or inside the empire's borders, and the agile horsemen of the Asian steppes than they did large forces such as those they stared down during the Punic Wars or other major conflicts. The logistical nimbleness and smaller armies trained to deal with the unique threats along the empire's borders allowed Rome to sustain her western empire for hundreds of years after expansion had stopped.
The western world today—the United States and Europe—finds itself in a position similar to that of the late Roman Empire. Despite renewed threats from Russia and an ascendant China, the chances of another great power or world war are small. Technological advances and the realities of a global economy upon which all the great powers depend make such unpalatable, even for the most bellicose. While we ought to be prepared for the possibility of such a conflict, it cannot be the primary focus. Take, for example, Russia's newfound antagonism in Georgia and more recently the Ukraine. Their strategy is not rooted in the overwhelming numbers of men that characterized its armies in the First and Second World Wars, but rather the use of combined technologies to create instability that allows relatively small numbers of soldiers to capitalize on the chaos. Similarly, the so-called War on Terror, now over a decade and a half old, requires the use of intelligence gathering and drones to conduct precise tactical strikes. Tank battalions may have helped keep the peace on the streets of Baghdad, but they can neither roll into the caves of Afghanistan, nor police cities across the United States and Europe. Ours is a world of cyber weapons and special forces, not one of the massive field armies that dueled across Europe and Asia during the 20th century.
The United States, protected by two oceans, only needs to equip large forces only to fight abroad, as they did during the World Wars or as is happening now in Iraq and Afghanistan. But occupation and nation-building efforts have proven ineffective applications of large forces, and a large defensive army for a conflict in Europe or Asia supposes an offense from a foe like Russia or China inconsistent with their respective efforts in Georgia, Ukraine, or the South China Sea. Such considerations must still be made, but they no longer represent the most likely, or most harmful, threat. Though Europe is not afforded the defensive geographic advantage America has, a large enough American force coupled with deterrence should prevent a wholesale invasion of the continent from Russia, but neither a nuclear shield nor an American presences can protect against the offense underway in eastern Ukraine.
As Western nations struggle with military budgets, politicians—particularly in the United States—need to consider what military dominance looks like in the 21st century, and in this regard they can learn from Rome. Valuable pieces of this puzzle have already appeared, describing how NATO's minnows can contribute to its collective defense, and how the United States can adapt to the role of the weaker foe. The bottom line, though, is that Rome sustained hegemony through adaptation, and western powers can too.
Some of these changes are already occurring, but in silos and absent an overarching strategic vision for how to combat the unique threats of the 21st century. The U.S. military, so long designed to conduct two full-scale conflicts in distinct geographic regions, now faces new types of enemies. In the current geopolitical environment, do military planners foresee a prolonged conflict against Russia AND China in the future? Do they envision two wars requiring the full might of the U.S. military, perhaps one in Africa and one in Asia? In fact Chairman of the Joint Chiefs of Staff, General Joseph Dunford’s 4+1 strategic framework imagines the threats from Russia, China, Iran, and North Korea—along with the shifting adversarial form of terrorism in the realms of land, air, sea, space, and cyberspace. Even Europe, fearful of a Russian invasion, is more likely to face the same type of border threats of the late Roman Empire. Russian meddling in Georgia and Ukraine is more akin to the quick and confusing strikes of tribesmen than the invasion of large army. Today’s foes threaten to undermine the global order carefully established and maintained in the aftermath of the Second World War the same way outlying tribes threatened the stability of the Roman world.
Sustaining today's global order requires new forms of fighting. Information has become weaponized. Intelligence gathering—always important—is now paramount as militaries, militias, and non-state actors, are equipped to strike immediately when they see opportunity rather than having to wait for the build-up and deployment of large bodies of soldiers. In many conflicts, members of the military are hundreds or even thousands of miles from the fighting, piloting drones remotely or hacking into electronic databases, meaning, as Albert Palazzo put it, “every nation’s homeland is now militarily in play.” Even when protected by oceans, a society is susceptible to cyberattacks. Evolution of weapons and tactics make it unlikely there will ever be another battle like Kursk, but there will absolutely be many more special forces raids and cyber attacks.
...where are defense initiatives aimed at partnering with private sector companies to protect society from new, chaotic, and unimagined attacks like those espoused in the Gerasimov doctrine?
Western strategists need to understand that maintaining a pro-western status quo does not involve turning back a Russian onslaught. It requires combatting Russian propaganda. Disinformation operations are a bigger threat to the liberal democratic order than tanks, and pending priorities ought to reflect this. With eleven aircraft carriers afloat as compared to two for Russia, is the United States preparing for another Midway? If so, no doubt they'll win. When such a battle fails to materialize, however, one wonders if the money spent to outfit such a fleet might have been better spent on more and better-equipped special forces, or on satellite weaponry to disable communications and weapons system without endangering a single life. In our modern society, with so much personal information available to nefarious actors around the globe, and within the particular context of the Russian cyberattack on the 2016 American election, where are defense initiatives aimed at partnering with private sector companies to protect society from new, chaotic, and unimagined attacks like those espoused in the Gerasimov doctrine?
Rome was able to deploy small, adaptive forces that struck at tribes outside the border, disrupting them militarily, economically, and politically before they became a threat. These troops could cover far larger stretches of the border than could much larger armies due to their speed, training, and a degree of independence from a centralized command structure atop which sat an emperor thousand of miles away from the borders they defended. An army of 80,000, similar to the one Hannibal annihilated at Cannae may have deterred bands of Germanic raiders...from crossing the border at the point it was stationed. But those raiding parties would and could have outpaced it to a weak spot in the line, crossing and wreaking havoc. The Romans understood that protecting their world order required a shift in strategic priorities away from overwhelming use of force to smaller but more tactically adroit units that were equipped to deal with the needs of the time. Will western politicians come to this same realization and pursue military spending that creates responsive forces suited to the needs of a new type of warfare? Or will we continue to maintain the illusion of safety relying on forces best suited for conflicts most likely confined to the past?
Will Staton is the Director of Scholar Support for Democracy Prep Congress Heights in Washington, DC. When he's not traveling the country to deliver professional development to teachers and other education professionals, Will nurses a deep interest in international and domestic politics. He contributes to The Strategy Bridge and other publications about domestic and international politics, and recently published his first novel, Through Fire and Flame, a modern rethinking of Dante's Inferno.
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Header Image: "The Death of Paulus Aemilius" at the Battle of Cannae, by John Trumbull, 1773 (Yale University Art Gallery/Wikimedia)
 For an accessible and wide-ranging history of these battles and Roman warfare in general, see Adrian Goldsworthy, Roman Warfare (New York, NY: Harper Collins, 2005).
Thomas J. Christensen, The China Challenge: Shaping the Choices of a Rising Power (New York, NY: W. W. Norton & Company, 2016), 40-49.
 Adrian Goldsworthy, Roman Warfare (New York, NY: Harper Collins, 2005)..