Event #7: Battle of Cannae, Roman army massacred by Hannibal

The Senate determined to bring eight legions into the field, which had never been done at Rome before, each legion consisting of five thousand men besides allies. …Most of their wars are decided by one consul and two legions, with their quota of allies; and they rarely employ all four at one time and on one service. But on this occasion, so great was the alarm and terror of what would happen, they resolved to bring not only four but eight legions into the field.

The Battle of Cannae (/ˈkæni/ or /ˈkæneɪ/) is a major battle of the Second Punic War that took place on 2 August 216 BC in Apulia, in southeast Italy. The army of Carthage, under Hannibal, decisively defeated a larger army of the Roman Republic under the consuls Lucius Aemilius Paullus and Gaius Terentius Varro. It is regarded both as one of the greatest tactical feats in military history and as one of the worst defeats in Roman history.

Having recovered from their losses at Trebia (218 BC) and Lake Trasimene (217 BC), the Romans decided to engage Hannibal at Cannae, with roughly 86,000 Roman and allied troops. The Romans massed their heavy infantry in a deeper formation than usual, while Hannibal utilized the double-envelopment tactic. This was so successful that the Roman army was effectively destroyed as a fighting force. Following the defeat, Capua and several other Italian city-states defected from the Roman Republic to Carthage.

In 216 BC, when elections resumed, Gaius Terentius Varro and Lucius Aemilius Paullus were elected as consuls, placed in command of a newly raised army of unprecedented size, and directed to engage Hannibal. Polybius wrote:

The Senate determined to bring eight legions into the field, which had never been done at Rome before, each legion consisting of five thousand men besides allies. … Most of their wars are decided by one consul and two legions, with their quota of allies; and they rarely employ all four at one time and on one service. But on this occasion, so great was the alarm and terror of what would happen, they resolved to bring not only four but eight legions into the field. ~ Polybius, The Histories

Eight legions, some 40,000 Roman soldiers and an estimated 2,400 cavalry, formed the nucleus of this massive new army. As each legion was accompanied by an equal number of allied troops, and allied cavalry numbered around 4,000, the army that faced Hannibal was likely no fewer than 90,000.

Ordinarily, each of the two consuls would command his own portion of the army, but since the two armies were combined into one, Roman law required them to alternate their command on a daily basis. The traditional account puts Varro in command on the day of the battle, and much of the blame for the defeat has been laid on his shoulders.[9] However, his low origins seem to be exaggerated in the sources, and Varro may have been made a scapegoat by the aristocratic establishment.[9] Varro lacked the powerful descendants that Paullus had: descendants who were willing and able to protect his reputation — most notably, Paullus was the grandfather of Scipio Aemilianus, the patron of Polybius. […]

The Romans were enclosed in a pocket with no means of escape. The Carthaginians created a wall and began destroying them. Polybius wrote, “as their outer ranks were continually cut down, and the survivors forced to pull back and huddle together, they were finally all killed where they stood.”

As Livy described, “So many thousands of Romans were dying… Some, whom their wounds, pinched by the morning cold, had roused, as they were rising up, covered with blood, from the midst of the heaps of slain, were overpowered by the enemy. Some were found with their heads plunged into the earth, which they had excavated; having thus, as it appeared, made pits for themselves, and having suffocated themselves.” 22.51 Cowley claims that nearly six hundred legionaries were slaughtered each minute until darkness brought an end to the bloodletting. Only 14,000 Roman troops managed to escape, most of whom had cut their way through to the nearby town of Canusium.

Polybius writes that of the Roman and allied infantry, 70,000 were killed, 10,000 captured, and “perhaps” 3,000 survived. He also reports that of the 6,000 Roman and allied cavalry, only 370 survived.

Livy wrote, “Forty thousand foot, two thousand seven hundred horse, there being an equal number of citizens and allies, are said to have been slain.” 22.49 He also reports that 3,000 Roman and allied infantry and 1,500 Roman and allied cavalry were taken prisoner by the Carthaginians. 22.49.18 Although Livy does not cite his source by name, it is likely to have been Quintus Fabius Pictor, a Roman historian who fought in and wrote on the Second Punic War. It is Pictor whom Livy names when reporting the casualties at the Battle of Trebia. 22.7.2–4 In addition to the consul Paullus, Livy goes on to record that among the dead were 2 quaestors, 29 of the 48 military tribunes (some of consular rank, including the consul of the previous year, Gnaeus Servilius Geminus, and the former Master of the Horse, Marcus Minucius Rufus), and 80 “senators or men who had held offices which would have given them the right to be elected to the Senate”.

Some modern historians, while rejecting Polybius’s figure as flawed, are willing to accept Livy’s figure. Some more recent historians have come up with far lower estimates. Cantalupi proposed Roman losses of 10,500 to 16,000. Samuels also regards Livy’s figure as far too high, on the grounds that the cavalry would have been inadequate to prevent the Roman infantry escaping to the rear. He doubts that Hannibal even wanted a high death toll, as much of the army consisted of Italians whom Hannibal hoped to win as allies.

Never when the city was in safety was there so great a panic and confusion within the walls of Rome. I shall therefore shrink from the task, and not attempt to relate what in describing I must make less than the reality. The consul and his army having been lost at the Trasimenus the year before, it was not one wound upon another which was announced, but a multiplied disaster, the loss of two consular armies, together with the two consuls: and that now there was neither any Roman camp, nor general nor soldiery: that Apulia and Samnium, and now almost the whole of Italy, were in the possession of Hannibal. No other nation surely would not have been overwhelmed by such an accumulation of misfortune. ~  Livy, on the Roman Senate’s reaction to the defeat

For a brief period, the Romans were in complete disarray. Their best armies in the peninsula were destroyed, the few remnants severely demoralized, and the only remaining consul (Varro) completely discredited. As the story goes, Rome declared a national day of mourning as there was not a single person who was not either related to or acquainted with a person who had died. The Romans became so desperate that they resorted to human sacrifice, twice burying people alive at the Forum of Rome and abandoning an oversized baby in the Adriatic Sea (perhaps one of the last instances of human sacrifices by the Romans, apart from public executions of defeated enemies dedicated to Mars).

Lucius Caecilius Metellus, a military tribune, despaired so much of the Roman cause as to suggest that everything was lost, and called the other tribunes to sail overseas and hire themselves into the service of some foreign prince. Afterwards, he was forced by his own example to swear an oath of allegiance to Rome for all time. The survivors of Cannae were reconstituted as two legions and assigned to Sicily for the remainder of the war as punishment for their humiliating desertion of the battlefield. In addition to the physical loss of her army, Rome suffered a symbolic defeat of prestige. A gold ring was a token of membership in the upper classes of Roman society; Hannibal and his men collected more than 200 from the corpses on the battlefield, and sent this collection to Carthage as proof of his victory. The collection was poured on the floor in front of the Punic Senate, and was judged to be “three and a half measures.”

Hannibal had defeated the equivalent of eight consular armies (16 legions plus an equal number of allies). Within just three campaign seasons (20 months), Rome had lost one-fifth (150,000) of the entire population of male citizens over 17 years of age. Furthermore, the morale effect of this victory was such that most of southern Italy joined Hannibal’s cause. After Cannae, the Hellenistic southern provinces of Arpi, Salapia, Herdonia, Uzentum, including the cities of Capua and Tarentum (two of the largest city-states in Italy) revoked their allegiance to Rome and pledged their loyalty to Hannibal. As Livy noted, “How much more serious was the defeat of Cannae than those which preceded it, can be seen by the behavior of Rome’s allies; before that fateful day, their loyalty remained unshaken, now it began to waver for the simple reason that they despaired of Roman power.” In the same year the Greek cities in Sicily were induced to revolt against Roman political control, while the Macedonian king, Philip V, pledged his support to Hannibal, initiating the First Macedonian War against Rome. Hannibal also secured an alliance with the new King Hieronymus of Syracuse, the only independent left in Sicily.

Hannibal’s conduct after the victories at Trasimene (217 BC) and Cannae, and the fact that he first attacked Rome only five years later, in 211 BC, suggests that his strategic aim was not the destruction of his foe but to dishearten the Romans by carnage on the battlefield and to wear them down to a moderate peace agreement by stripping them of their allies.

Immediately after Cannae Hannibal sent a delegation led by Carthalo to negotiate a peace treaty with the Senate on moderate terms. Despite the multiple catastrophes Rome had suffered, the Senate refused to parley. Instead, they redoubled their efforts, declaring full mobilization of the male Roman population, and raised new legions, enlisting landless peasants and even slaves. So firm were these measures that the word “peace” was prohibited, mourning was limited to only 30 days, and public tears were prohibited even to women. (Dodge, Theodore. Hannibal. Cambridge, Massachusetts: Da Capo Press, p.386) For the remainder of the war in Italy, they did not amass such large forces under one command against Hannibal; they utilized several independent armies, still outnumbering the Punic forces in numbers of armies and soldiers. The war still had occasional battles, but was focused on taking strongpoints and constant fighting according to the Fabian strategy. This finally forced Hannibal with his shortage of manpower to retreat to Croton from where he was called to Africa for the battle of Zama, ending the war with a complete Roman victory.

Cannae played a major role in shaping the military structure and tactical organization of the Roman Republican army. At Cannae, the Roman infantry assumed a formation similar to the Greek phalanx. This left them vulnerable to Hannibal’s tactic of double envelopement since their inability to maneuver independently from the mass of the army made it impossible for them to counter the strategic encirclement used by the Carthaginian cavalry. The laws of the Roman state requiring command to alternate between the two consuls restricted strategic consistency.

In the years following Cannae, striking reforms were introduced to address these deficiencies. First, the Romans “articulated the phalanx, then divided it into columns, and finally split it up into a great number of small tactical bodies that were capable, now of closing together in a compact impenetrable union, now of changing the pattern with consummate flexibility, of separating one from the other and turning in this or that direction.” ( Peter Paret, Gordon A. Craig, Felix Gilbert, Makers of Modern Strategy from Machiavelli to the Nuclear Age (Princeton, N.J.: Princeton University Press, 1986), page 337.) For instance, at Ilipa and Zama, the principes were formed up well to the rear of the hastati—a deployment that allowed a greater degree of mobility and maneuverability. The culminating result of this change marked the transition from the traditional manipular system to the cohort under Gaius Marius, as the basic infantry unit of the Roman army.

In addition, a unified command came to be seen as a necessity. After various political experiments, Scipio Africanus was made general-in-chief of the Roman armies in Africa, and was assured this role for the duration of the war. This appointment may have violated the constitutional laws of the Roman Republic but, as Delbrück wrote, it “effected an internal transformation that increased her military potentiality enormously” while foreshadowing the decline of the Republic’s political institutions. Furthermore, the battle exposed the limits of a citizen-militia army. Following Cannae, the Roman army gradually developed into a professional force: the nucleus of Scipio’s army at Zama was composed of veterans who had been fighting the Carthaginians in Hispania for nearly sixteen years, and had been moulded into a superb fighting force.

Apart from being one of the greatest defeats inflicted on Roman arms, Cannae represents the archetypal battle of annihilation, a strategy that has rarely been successfully implemented in modern history. As Dwight D. Eisenhower, the Supreme Commander of the Allied Expeditionary Force in World War II, wrote, “Every ground commander seeks the battle of annihilation; so far as conditions permit, he tries to duplicate in modern war the classic example of Cannae”. Furthermore, the totality of Hannibal’s victory has made the name “Cannae” a byword for military success, and is studied in detail in military academies around the world. The notion that an entire army could be encircled and annihilated within a single stroke led to a fascination among Western generals for centuries (including Frederick the Great and Helmuth von Moltke), who attempted to emulate its tactical paradigm of envelopment and re-create their own “Cannae”. (Cowley, Robert (ed.), Parker, Geoffrey (ed.) The Reader’s Companion to Military History, “Battle of Cannae”. Houghton Mifflin Company, 1996) Delbrück’s seminal study of the battle had a profound influence on German military theorists, in particular the Chief of the German General Staff, Alfred von Schlieffen, whose eponymous “Schlieffen Plan” was inspired by Hannibal’s double envelopment maneuver. Schlieffen taught that the “Cannae model” would continue to be applicable in maneuver warfare throughout the 20th century:

A battle of annihilation can be carried out today according to the same plan devised by Hannibal in long forgotten times. The enemy front is not the goal of the principal attack. The mass of the troops and the reserves should not be concentrated against the enemy front; the essential is that the flanks be crushed. The wings should not be sought at the advanced points of the front but rather along the entire depth and extension of the enemy formation. The annihilation is completed through an attack against the enemy’s rear… To bring about a decisive and annihilating victory requires an attack against the front and against one or both flanks…

Schlieffen later developed his own operational doctrine in a series of articles, many of which were translated and published in a work entitled Cannae.

Sources:

Carlton, James. The Military Quotation Book. New York City, New York: Thomas Dunne Books, 2002.
Daly, Gregory. Cannae: The Experience of Battle in the Second Punic War. London/New York: Routledge.
Delbrück, Hans. Warfare in Antiquity, 1920, ISBN 0-8032-9199-X.
Hoyos, Dexter B. Hannibal: Rome’s Greatest Enemy. Bristol Phoenix Press, 2005.
Church, A. J. and Brodribb, W. J. English translation: Livy, Books 21-25, The Second Punic War, Macmillan 1893. See pp. 103–124.
Livy, Titus Livius and De Selincourt, Aubrey. The War with Hannibal: Books XXI-XXX of the History of Rome from its Foundation. Penguin Classics, Reprint Edition, 1965.
Talbert, Richard J. A. (ed.) Atlas of Classical History. London/New York: Routledge, 1985