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John Sloan

  In this essay we hope to provide a short but complete analysis of the battle. Most books and articles on this battle provide excellent context with descriptions of the whole Second Punic War and sometimes of all three of the wars. The best books include much detail on the political context and sometimes the cultural or economic contexts as well. But this essay is focused on the battle itself with only the minimum background necessary. See the main page on Roman history for links to other related essays.  

Lets look at Cannae.

Strategy and strategic objectives

Composition and structure of the Roman and Carthaginian army at Cannae.

Roman command - Paullus was the real commander in chief - he was experienced and a successful general - Varro had not been a general but had been an officer in combat. The previous consul and master of horse were also present and commanding in the battle.

Later Roman historians had to find a scape goat and chose Varro because they were glorifying the gens of Paullus's family.

Carthaginian command - of course Hannibal although under 30 had years of experience - his brother Mago and the other officers also were long service professionals.

Roman army

In 216 the Romans had 17 legions in the field (always remember each legion had a partner allied comparable force). Plus the Romans had at least a legion worth of marines on board the navy at Ostia and the allies had garrisons in several hundred fortified towns.

Typical summary accounts don't provide the detail that Toynbee and German authors do. There are various numbering systems for legions based on their recruitment dates. Now Roman soldiers were peasant farmers with net worth above a specific standard. They were conscripted for annual service - but due to this war were kept on service until killed or wounded. The Allied soldiers were double conscripts - that is they were offered up by their towns and villages or tribes as individual conscripts after the Roman senate sent a conscription notice to the individual town specifying how many conscripts were required.

They were sent in average detachments of 500 or so from about 40 Latin towns and between 135 and 150 independent sovereign tribes and towns. For instance when Hannibal negociated with Capua to change sides the authorities there pointed out that they had a 500 man unit serving the Romans in Sicily and wanted Hannibal to offer up 500 of his Roman prisoners so they could be exchanged (didn't work).

At any rate at Cannae there were some 40,000 of these allied infantry conscripted at the same time as the 40,000 Roman infantry men.

Now lets look at the Romans legion by legion 1 and 2 recruited in 218 for service in Sicily to invade Africa and rushed then to Po valley where they fought and escaped at Trebbia. - In 217 they remained in Gallia and in 216 moved south to form the only really experienced legions at Cannae (with their allied detachments remember) 3 and 4 were recruited in 218 survived Trebbia and were destroyed at Lake Trasimene 5 and 6 were recruited in 218 and sent to Spain with the two elder Scipios where they were destroyed in 210. 7 and 8 were recruited in 217 and replaced 1 and 2 in Sicily and were brought back to Apulia in 214 and destroyed in 211. 9 was recruited in 217 and sent to Sardinia were it remained for the war 10 and 11 were recruited in Roma to defend the city after Trasimene -they were sent north to Gallia in 216 where they were destroyed by the Celts a few days after Cannae. 12 and 13 were recruited in 217 and served with Fabius in the skirmishes and small battles of that year - they were reasonably trained in other words but destroyed at Cannae. 14 and 15 were recruited in 216 for the original consuls and destroyed at Cannae 16 and 17 were recruited in early 216 for the second set of consuls ( Paullus and Varro) and brought with them to Cannae a couple weeks prior to the battle in which they were destroyed. 18 and 19 replaced the previously destroyed legions in the Po Valley 20 and 21 were newly raised to replace 16 and 17 as garrison of Rome So the Roman army at Cannae had 2 experienced legions in service for 2 years - 2 in service for a year and a half - and 4 newly raised legions - Plus of course the longer serving 4 legions had hundreds of replacement recruits to fill up their losses.

Is it any wonder the two consuls planned on a tactical deployment to preserve their troops?

The survivors of Cannae were formed into two legions and exiled to Sicily were they served until they formed to basis of Scipio's new army for the Zama campaign - more about that later - some of them were then sent to Greece to fight Macedon. The Roman senate was an implacable task master - they refused to exchange prisoners with Hannibal - letting him sell the lot into slavery in Greece and Crete - and they exiled the troops who did escape Cannae and other battles.

Roman cavalry

The Roman cavalry was actually horsemen, not real cavalry, composed of wealthy young men aspiring for future careers. 6 or 7 thousand of these guys had already been killed off in 218 and 217. They of course didn't have stirupps and often fought on foot. The allied cavalry were much better, coming from the horse breeding sections of southern Italy - but they too had already lost quite a few of their experienced troopers. When they observed the Carthaginian heavy cavalry coming at their rear they bugged out for home forth with.

Carthaginian army

O'Connell is right in describing these folks as professional killers. The largest contingent - Celts from Po valley had been at war with Rome for generations and seen their fathers and relatives killed at Telamon and in the Po valley - it took the Romans another generation to complete their conquest. The Celt-Iberians were from mountain tribes in modern Spain who continued to fight Rome for over another 100 years.

The Balearic slingers were experts and renowned throughout the Med region and were also the most primitive culturally of the lot - \

The Africans - Lybians were professional mercenaries who had fought for over 10 years under Hannibal's father and brother in law in Spain. Hannibal re-armed these 10,000 or so with captured Roman arms and armor.

The Celtic and Iberian cavalry were also professionals much more heavily armed than the Romans - the Iberians wore armor as well. And the Numidian cavalry were nomads - described as the closest thing to Tatar -Scythian steppe warriors ever found in the west. They simply toyed with the Roman allied cavalry as needed. So all these guys were from cultures that stressed heroic deeds in battle

The Roman army, as already noted, outnumbered the Carthaginians in infantry almost 2 to 1 but the Carthaginians held a 10 to 6 ratio in cavalry, plus their cavalry was recognized as being much the better. The prior Carthaginian successes had come from their superior cavalry outflanking the Roman line and executing envelopments. But at Trebbia and Trasimene a solid core of Roman infantry had managed to break through the Carthaginian infantry line. Now both armies encamped in fortified camps on the north side of the Aufidius River. This was a wide open plain. An experienced general with excellent troops might have wanted to deploy there in a long line and be able to outflank both ends of a thinner Carthaginian line. But the Roman generals were 1 afraid of Hannibal's cavalry and 2 well aware of the inexperience of most of their own infantry. Therefore they on purpose on the day of battle marched south across the river and deployed in a narrow - flat - space between the river on their right side and the ridge on which stood Cannae ruin on their left side.

They on purpose hoped to negate Hannibal's cavalry by deploying their own on their flanks as usual but with orders to assume defensive tactics and only protect the flanks of their massed infantry plus having both flanks secured by terrain..

Hannibal watched this maneuver starting and had to figure out a way to counter it by using his cavalry to best effect anyway plus create a typical ambush in plain sight on a plain. So he deployed his Balaeres across the river first to set up a screen along with some javelin throwers. Then he marched his main forces across in several columns - and posted his best Celtic- Iberian cavalry on his left outnumbering the Romans - and his Nummidian cavalry on the right in numbers almost equal to the Roman allies and with orders to skirmish and simply hold them in place - which unfortunately was exactly all the Roman allied cavalry was tasked to do any way. But the Celtic-Iberian cavalry was tasked to smash the Roman cavalry quickly at the start of the battle - which they did. Behind his Balleric slingers Hannibal deployed his Celt and Iberian infantry - in subunits mixed along the line so the Iberians using the Spanish sword were interspersed with the Celts using their lengthy slashing swords. Right off this would cause the Romans some problem in dealing with the two very different fighting styles.

Then BEHIND the cavalry Hannibal deployed his best - the African professionals now armed with Roman weapons in COLUMNS - one on each side. They were hidden in plain view.

Meanwhile - in the purposely constricted width of the battlefield the Romans deployed at about half width and double depth- thinking they would form a phalanx and crush the Carthaginian center. BUT the narrower the Roman deployment the deeper the Carthaginian deployment could be and was.

Now came the genius part - Hannibal advanced the central sub-units of his main line a significant distance - thus in effect refusing both flanks of his line. The slingers and javelin throwers did their thing knocking out the poorly armed and trained Roman light infantry - both sides then retired behind their main line of battle. But not before the slingers had already put Consul Paullus almost out of action from a hit from a sling stone. No one comments about unknown details - but I suspect that given the ability of these slingers to put a lead bullet into a small circle target at 100 yards or more they were aiming whenever they could at Roman officers. At any rate Hannibal's deployment served its purpose. The 16 semi-independent Roman columns advanced - and as we know from a parade ground it was quite an effort to keep all 16 on line - result only the central Roman legions engaged the center of the Carthaginian line while their wings held their positions- critical for this kind of battle. This delayed the increasing intensity of the fight in the infantry line while Hannibal's elite cavalry killed and drove off the Roman cavalry - Hannibal had his central units fall back gradually thus bringing more of the line into action but also causing the Romans naturally to bunch up a bit toward the center. The Carthaginian line gradually shifted from being convex toward the Romans to straight and then concave as the Roman infantry sensed victory and pushed more and more to make the desired breakthrough. But by now the Carthaginian cavalry from their left flank had ridden clear around the Roman army and approached the allied cavalry on the Roman left from the rear - seeing this the allies bugged out without waiting

But now the Roman legions were deep into the cul de sack Hannibal had created - and those two 5000 man masses of Lybian infantry standing in columns - who knows how many files by how many ranks, were now revealed to be standing patiently outside the right and left flank of this Roman mass -and armed in Roman armor. They might be 50 by 100 or 25 by 200 or whatever. Whatever, they over whelmed the Romans they faced. All they had to do was face right or left and attack a Roman formation that was at most 100 men deep - that is of course wide from the point of view of the Lybians - moreover - on the Roman right they were attacking on the vulnerable - shieldless side and on the Roman left the less reliable allied units. This was a tour de force of economy of force tactics.

At this point or soon after Hasdrubal showing his supremacy as a cavalry commander - let the allied cavalry flee pursued by the Nummidians and instead rallied his troopers, almost 6000 of them remaining - difficult to do with cavalry - and attacked the vulnerable rear of the Roman formation - which was where some15,000 velites - the light infantry - were milling about. The Roman heavy infantry, such as it was, didn't even get a chance to form a resistance line against this cavalry. The Roman mass had to stop - the Celt and Iberian infantry then could shift from defense to offense against the front of this mass. At the same time the slingers could fire over the heads of their infantry associates and hit the Romans throughout the length and breadth of the mass.

So the result was that the Romans did prevent being attacked in the flank by Hannibal's cavalry but instead were attacked in the flank by his best infantry units while part of his cavalry completed an encirclement.


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