Comparing the armies of entirely different historical periods or cultures, and trying to work out which would win in some anachronistic clash of arms, is generally a fairly futile pursuit. Military forces develop in response to the specific needs of their day, and rely on the available technology of their era. Nevertheless, this hasn’t stopped people trying to imagine the results, and while some of these fantasy confrontations are more fanciful than others (Vikings vs. Ninjas?), the idea of a battle between Imperial Rome and the knightly warriors of the Middle Ages has long been a recurring topic for internet historians, armchair strategists and wargamers of all sorts.
Putting aside the obvious objections, therefore: if we imagined that a Roman army and an army of Medieval Europe were somehow sucked through a rent in the space-time continuum and compelled to fight a battle, is there any way of guessing who might come off best?
To try and answer the question, we’d first have to decide on some representative forces. The Roman army of the 2nd century BC was very different to that of the 4th AD, just as the armies of the 10th century differed greatly from those of the 15th. But the Roman empire was vast, far larger than any medieval state; a single legion with its auxiliaries could have outnumbered the average force deployed by a king of the earlier middle ages. So we’d need to choose opponents of a similar size, a suitable era, and of which we have a fairly detailed description.
Even so, the match would be difficult. The Roman army was based on the heavy infantry legion, developed to beat opponents who mainly fought on foot. The armies of the medieval era, on the other hand, were centred on the heavily armoured aristocratic knight, usually mounted before the 14th century, and supported by a range of foot soldiers. To make our imaginary clash more equitable, we’d have to choose opponents that had in some way adapted to fighting outside their tactical comfort zone: Romans who went up against a largely mounted enemy, versus knights with some experience of battling largely infantry foes.
For the Romans, then, I’ve selected the force described by Lucius Flavius Arrianus – better known today as Arrian – in his Acies contra Alanos. Arrian was a Roman senator and governor of Cappadocia, of Greek origin, and his Greek account details the composition and tactics of an expeditionary force he led, or intended to lead, against the invading Alanic horse nomads in AD135. Arrian appears to have led two legions, five cavalry units and around ten cohorts of auxiliaries, three of which may have been of double size. On paper his force possibly numbered about 19,000 men, but few units were ever at full strength; 15,000 seems a more likely figure, of which 8000 were legionary infantry and around 2000 cavalry. Eight of his auxiliary cohorts included a mounted component, and at least three also included archers. Crucially, his army also included an artillery section of catapults and ballistae; the late Roman writer Vegetius suggests that each legion may have had 55-65 of these machines.
As a suitable medieval force to oppose the might of Rome, I’ve chosen the Anglo-Welsh army led by King Edward I of England against the Scots in 1298. The English had been beaten the year before by a Scottish army that included large numbers of infantry pikemen fighting in blocks called schiltrons – perhaps the closest medieval battlefield equivalent to an ancient infantry array. Numbers for Edward’s army are harder to establish with any great accuracy, but he probably had around 2500 cavalry – most of them fully armoured knights and men-at-arms. This time, however, he was better prepared to deal with the Scots schiltrons, and his knights were supported by around 12,500 infantry, many of whom were longbowmen from Wales and northern England.
Arrian’s tactics are far more defensive than the usual Roman style of fighting against opponents on foot. He first selects a suitable location with high ground on either side to prevent outflanking moves by the mobile enemy, then draws up his legions in a strong line eight ranks deep, forming a wall of shields with the light troops on the flanks and the archers and artillery at the rear. Even trained cavalry horses will not generally charge against a solid wall of infantry, and Arrian intends to hold his position and break the impetus of the Alanic assault with volleys of javelins, arrows and artillery projectiles. Once the Alans are in disarray, the infantry will open lanes and allow the Roman cavalry to charge through them and drive the enemy from the field.
Medieval tactics of the 13th century were also fairly simple, and relied on the power of the charging mounted knight. Knights were formidable warriors, trained since childhood in combat and accustomed to regular exercise in hunting and the mock battles of the tournament, even when they were not on active campaign. Edward’s horsemen would be dressed from head to foot in mail, with full helmets and plate limb defences, and armed with lances, swords and shields; some were also mounted on armoured horses. But at Falkirk, the most important aspect of the English army was the longbowmen: rather than charge directly against the Scots infantry, Edward ordered his archers to shower them with mass volleys of arrows, only sending in his knights and mounted men-at-arms when the enemy formations had frayed and gaps had opened in their ranks. The combination was deadly – but how well would it have worked against Arrian’s Romans?
Rome had faced large numbers of archers before, and large numbers of mounted cavalry too. The Parthians had beaten a Roman army at Carrhae in 53BC using massed archery to wear down the legionaries, followed by horseback charges, just as Edward did against the Scots. But the Romans had learned from their mistakes, and managed to defeat the Parthians, and later the Persians, several times in open battle. The disciplined ranks of Arrian’s armoured legionaries would perhaps have stood up to archery much better than the Scots levy pikemen at Falkirk. Besides, the Romans had archers too, and every legionary carried one or more heavy javelins as close-range missile weapons. They also had artillery, of course, although with the catapults positioned behind the infantry lines it would have been difficult to use them as sniper weapons, as the Romans sometimes did, and pick off the leaders of the enemy horsemen. Arrian does not mention caltrops (tribuli) – spiked obstacles strewn on the ground to cripple men and horses – perhaps because he intends to send his own cavalry forward through the front lines. If this was not an option, the Romans may have used caltrops as well to break up any advancing enemy.
We don’t know for sure whether the longbows used by Edward’s archers in 1298 were as powerful as those of the following century, but they may have had a draw weight of more than 100lb. These bows would have shot much further and harder than the smaller bows used by the Romans; only Arrian’s artillery could have matched their range. But while the 100 or so Roman ballistae could each release around 3 bolts a minute, Edward’s thousands of archers could shoot an arrow every seven seconds. If the English were supplied with unlimited ammunition, they could feasibly keep on pelting the Romans with arrows until the legionary formation broke, as the Parthians had done at Carrhae. The arrow storm would perhaps not kill too many of the Romans directly, but with the effort of keeping their shields raised against the missiles the Romans would have little strength to do much except defend themselves.
If the Romans could maintain their formation and withstand the withering volleys from the powerful English longbows, they could also hold off any charges from the mounted knights. However, their offensive capability would be gone: if they attempted a charge on foot, they would be cut to pieces, and their cavalry would be of little use: the medieval warhorse was far larger than anything known in the ancient world, and the Roman cavalrymen would stand little chance against the knights in open combat.
However, even with their ranks frayed the Romans would still have presented a formidable obstacle to Edward’s battle-winning knights. Barring a sudden lucky charge, the English horsemen would be unlikely to get close enough to the legionary ranks to force a gap in their line. Any individual knight who managed to brave the storm of missiles, the caltrops and the javelins and break through the wall of shields would be swiftly surrounded, brought down and battered to death with blunt instruments: the Romans’ favoured way of despatching armoured opponents.
On the face of it, the battle looks like a stalemate.
At this point, therefore, we have to consider the skill of the opposing leaders. Edward I was reputedly one of the best military commanders in Europe (even if he said so himself), while we have, unfortunately, little idea of the true martial abilities of Flavius Arrianus. Once battle was joined, maintaining discipline and morale would be as important as tactics. A Roman commander like Julius Caesar, Domitius Corbulo or the Emperor Trajan could well have motivated his troops to withstand a lengthy battle of attrition, and perhaps found a way to take the fight to the enemy. Edward was clearly an exceptional leader of men, and perhaps could have inspired or cajoled his knights into a mass frontal attack against the odds. But with their forces so evenly matched, it would take either luck or a crafty bit of generalship to force anything more than a lengthy and very bloody stand-off.
With this kind of consideration in mind, we can appreciate that warfare of any era is far more than a simple comparison of strengths and tactics. Victory is seldom a matter of calculation, but relies on an unquantifiable balance of skill, morale, discipline and plain luck. It’s worth bearing in mind, too, that while the armies of 2nd century Rome and of 13th century Europe were supremely effective in their day, both evolved to face changing threats and to reflect changing societies. And while a single battle may decide a conflict, to gain a true idea of the military capabilities of a past society, we’d need to look at the larger picture. The true strength of the Roman military lay not so much in its legions, as in the vast supply and logistics network that allowed the legions to keep on functioning during lengthy campaigns. The Romans may have lost battles, but they seldom lost wars.