Phase 6

The Southern Roman Campaign

  While the Romans were busy raising an army and sorting out political/religious matters, Hannibal had marched in a leisurely manner south from Hartia. His army, rested, restored to health, retrained and re-equipped, cut a path of destruction through central Italy as they collected grain, cattle, provisions and supplies during the march. Hannibal followed the coastal plain before turning west. Near the town of Arpi, the Roman army under Fabius Maximus made contact with the Carthaginian army and camped at Aecae, six miles away from the Carthaginian camp (Lazenby, John Francis, Hannibal's War p68).

Remains of the town of Arpi

  Hannibal drew up his army and offered battle, but Fabius Maximus ignored the offer and the Roman army remained in their camp. Pliny also enumerates that Aecani was among the inland towns of Apulia (iii. 11); but its position is more clearly determined by the Itineraries, which place it on the Appian Way between Equus Tuticus and Herdonia, at a distance of 29 to 31 kilometers (18 to 19 mi) from the latter city (Antoine Itinerary p. 116;).   It was located in south central Italy so by this time Hannibal had passed up Rome to the east while heading south.

Fabius Maximus Cunctator (the Delayer)

   Having ravaged Apulia without provoking Fabius Maximus into battle Hannibal decided to march through Samnium and Campania.

Ancient Map of Samnium and Campania

  Apulia covers an area of about 7,336 miles.  So he was moving from the east coast of Italy to the west coast of Italy. Campania was one of the richest and most fertile regions of Italy, hoping that devastation there would draw Fabius in battle the latter was aware that there were excellent opportunities to trap the Carthaginians on the Campania plain and to force Hannibal to fight in the surrounding mountains or the ground of his own choice.  As the year wore on, Hannibal realized that it would be unwise to winter in the already devastated lowlands of Campania, but Fabius had ensured that all the passes out of Campania were blocked.  The situation led to a diversion at night in which the Carthaginians made good their escape by tricking the Romans into believing they were heading for the heights through the forest above them. The Carthaginians decoyed the Roman’s attention and slipped through the pass undetected with all their baggage train. Fabius was within striking distance but in this case, his caution worked against him. Smelling a stratagem (rightly), he stayed put. 

    For the winter, Hannibal found comfortable quarters in the Apulian plain. What Hannibal achieved in extricating his army was, as Adrian Goldsworthy puts it, "a classic of ancient generalship, finding its way into nearly every historical narrative of the war and being used by later military manuals" (Goldsworthy, Adrian K. The Roman Army at War  100 BCE — AD CE).  This was a severe blow to Fabius' prestige and soon after this, his period of dictatorial power ended.  Apulia is a region of in Southern Italy bordering the Adriatic Sea in the east, the Ionian Sea to the southeast, and the Strait of Òtranto and Gulf of Taranto in the south.  Its southernmost portion, known as Salento peninsula, forms a high heel on the "boot" of Italy. 

  Apulia is one of the richest archaeological regions in Italy. It was first colonized by Mycenaean Greeks (Elizabeth A. Fisher, The Mycenaeans and Apulia). During the 8th century BCE, the Ancient Greeks expanded until reaching the area of Taranto and Salento in Greater Greece. In the 5th and 4th centuries BCE, the Greek settlement at Taras produced a distinctive style of pottery.  Apulia was an important area for the ancient Romans, who conquered it during the course of wars against the Samnites and against Pyrrhus in the 4th and 3rd centuries BCE.  Apulia was an area, which produced grain and olive oil

  Minucius, the Master of Horse under Fabius, who was one of the leading critics in the army against the adaptation of the Fabian strategy as soon as he secured a minor success, by winning a skirmish with the Carthaginians, the Senate promoted Minucius to same imperium (power of command) as Fabius when he was accused of cowardice.  Fabius became unpopular in Rome since his tactics did not lead to a quick  

 Fabius used attrition warfare against Hannibal, cutting off his supply lines and avoiding pitched battles. These tactics proved unpopular with the Romans, who, as they recovered from the shock of Hannibal's victories, began to question the wisdom of the Fabian strategy that had given the Carthaginian army a chance to regroup (Liddell Hart, Basil. Strategy).  Therefore, when Fabius’ term ended, the Senate did not renew his dictatorial powers.   The consuls Gnaeus Servilius Geminus and Marcus Atilius Regulus were appointed to command at first. But in 216 BCE, when elections resumed, Gaius Terentius Varro and Lucius Aemilius Paullus were elected as consuls, and placed in command of a newly raised army of unprecedented size, and directed them to engage Hannibal and end the war. 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 of Polybius ("Internet Ancient History Sourcebook").

  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 less than 90,000 (Cottrell, Leonard. Enemy of Rome). However, some have suggested that the destruction of an army of 90,000 troops would be impossible. They argue that Rome probably had 48,000 troops and 6,000 cavalry against Hannibal's 35,000 troops and 10,000 cavalry (The Cambridge Ancient History VIII: Rome and the Mediterranean 218–133 BCE). Livy quotes one source stating the Romans added only 10,000 men to their usual army (Livy. The History of Rome by Titus Livius: Books 9 

- Twenty-Six, trans. D. Spillan and Cyrus Edmonds).  While no definitive record of the number of Roman troops exists, all sources agree that the Carthaginians faced a considerably larger foe.

  In the spring of 216 BCE, Hannibal took the initiative and seized a large supply depot at Cannae, in the Apulian plain, placing himself between the Romans and their crucial source of supply.

   As Polybius noted, the capture of Cannae "caused great commotion in the Roman army; for it was not only the loss of the place and the stores in it that distressed them, but the fact that it commanded the surrounding district"("Internet Ancient History Sourcebook).   The consuls, resolving to confront Hannibal, marched southward in search of him. After two days' march, they found him on the left bank of the Aufidus River, and encamped six miles (10 km) away.

The Aufidus River Today

There were two Roman bridges that crossed the River, one further upstream and another closer to Hannibal’s position.  The Aufidus River (the modern Ofanto River) cuts the Apulia region in half and its source is in Campania from there it flows into the Adriatic Sea. The River is about 170 miles long.

  Reportedly, a Carthaginian officer named Gisgo commented on how much larger the Roman army was. Hannibal replied, "Another thing that has escaped your notice, Gisgo, is even more amazing—that although there are so many of them, there is not one among them called Gisgo"(Lazenby, J.F. Hannibal's War).

  After the campaigns in 217 BCE, Hannibal had failed to obtain a following by the Italian people who lived near Rome, or the Latin areas, or in southern Italy such as the Campania.  The Roman senate authorized the raising of double-sized armies by the Consuls Gaius Varro and Aemilius Paulus.  By some estimates, the Romans had raised an army possibly as large as 100,000 men, although this figure may not be accurate.

    The Consul Gaius Terentius Varro was considered by contemporary sources as a man of reckless nature and a man of extreme pride, who was determined to defeat Hannibal. While the Romans were approaching Cannae, a small portion of Hannibal's forces ambushed them. Varro successfully repelled the attack and continued on his way to Cannae. This victory, though essentially a mere skirmish with no lasting strategic value, greatly bolstered the confidence of the Roman army, perhaps to overconfidence on Varro's part. Lucius Aemilius Paulus, however, was opposed to the engagement as it was taking shape. Unlike Varro, he was prudent and cautious, and he believed it was foolish to fight on open ground, despite the Romans' numerical strength. This was especially true since Hannibal held the advantage in cavalry (in both quality and quantity).  Despite these misgivings, Lucius Aemilius Paullus thought it unwise to withdraw the army after the initial success, and camped two-thirds of the army east of the Aufidus River, sending the remainder to fortify a position on the opposite side. The purpose of this second camp, was to cover the foraging parties from the main camp and harass those of the enemy (Cottrell, Leonard. Enemy of Rome).

Roman Bridge near Cannae

  The two armies stayed in their respective locations for two days. During the second day (August 1), Hannibal, aware that Varro would be in command the following day, left his camp and offered battle, but Paullus refused. When his ploy did not work, Hannibal, recognizing the importance of the water from the Aufidus to the Roman troops sent his cavalry to the smaller Roman camp to harass water-bearing soldiers outside of the camp fortifications. According to Polybius ("Internet Ancient History Sourcebook").   Hannibal's cavalry boldly rode up to the edge of the Roman encampment, causing havoc and thoroughly disrupting the supply of water to the Roman camp (Caven, B. Punic Wars).

    The Carthaginian army was a combination of warriors from numerous regions. Along with the core of 8,000 Libyans, there were 8,000 Iberians, 16,000 Gauls (8,000 were left at camp the day of battle) and around 5,500 Gaetulian infantry. Hannibal's cavalry also came from diverse backgrounds. He commanded 4,000 Numidian, 2,000 Iberian, 4,000 Gallic and 450 Liby-Phoenician cavalry. Finally, Hannibal had around 8,000 skirmishers consisting of Balearic slingers and mixed nationality spearmen, totaling around 47,950 men. The uniting factor for the Carthaginian army was the personal tie each group had with Hannibal (Daly, Gregory. Cannae: The Experience of Battle in the Second Punic War).

  Rome's forces used typical Roman equipment including pila (heavy javelins) and hastae (thrusting spears) as weapons as well as traditional helmets, shields and body armor.

Roman Heavy Infantry in the Roman Republic

  On the other hand, the Carthaginian army used a variety of equipment. The Iberians fought with swords suited for cutting and thrusting, as well as javelins and various types of spears. For defense, Iberian warriors carried large oval shields and the falcata.

The Iberian Falcata

The Gauls were likely wearing no armor, and the typical Gaulish weapon was usually a long, slashing sword (Polybius, Penguin Classics translation).  The heavy Carthaginian cavalry carried two javelins and a curved slashing sword, with a heavy shield for protection. The Numidian cavalry were very lightly equipped, lacking saddles and bridles for their horses, and used no armor but carried small shields, javelins and possibly a knife or longer blade. Skirmishers acting as light infantry carried either slings or spears. The Balearic slingers, who were famous for their accuracy, carried short, medium and long slings used to cast stones or bullets. They may have carried a small shield or simple leather pelt on their arms, but this is uncertain. Hannibal wore Musculata armor and carried a falcata as well (Daly, Gregory. Cannae: The Experience of Battle in the Second Punic War, pp. 107–108).

Muscle Cuirass (or Musculata) worn by Hannibal

   It has been much debated how the Libyan line infantry was armed. Head has argued in favor of short stabbing spears (Duncan Head, Armies of the Macedonian and Punic Wars). Polybius states that the Libyans fought with equipment taken from previously defeated Romans. It is unclear whether he meant only shields and armor or offensive weapons as well (Daly, Gregory. Cannae: The Experience of Battle in the Second Punic War, p. 89.)  A general reading suggests Polybius meant the whole panoply of arms and armor and even tactical organization. Apart from his description of the battle itself. Polybius later discussing the subject of the Roman legion versus the Greek phalanx, says that: "...against Hannibal, the defeats they suffered had nothing to do with weapons or formations" because, "Hannibal himself...discarded the equipment with which he had started out (and) armed his troops with Roman weapons" (Polybius, Penguin Classics translation, p.509).   Dally is inclined to the view that Libyan infantry would have copied the Iberian use of the sword during their fighting there so was armed similarly to the Romans (Daly, Gregory. Cannae: The Experience of Battle in the Second Punic War, p. 90).

     The conventional deployment for armies of the time was placement of infantry in the center, with the cavalry in two flanking "wings". The Romans followed this convention closely, but chose extra depth rather than breadth for the infantry, hoping to use this to break through the center of Hannibal’s line. Varro knew how the Roman infantry had managed to penetrate Hannibal's center at Trebia, and he planned to recreate this on an even greater scale. 

  The Principes located immediately behind the Hastati, ready to push forward at first contact to ensure the Romans presented a unified front. 

As Polybius wrote, "the maniples were nearer each other, or the intervals were decreased...and the maniples showed more depth than front"(Dodge, Theodore. Hannibal).   Even though they outnumbered the Carthaginians, this depth-oriented deployment meant that the Roman lines had a front of roughly equal size to their numerically inferior opponents.

  The Roman army was organized into three lines: the Hastati, the Principes, and the Triarii.

The Triari were the most experienced of the Roman soldiers

  These soldiers were placed according to their experience, with the youngest soldiers the Hastati making the first engagement. Where resistance was strong, this rank would dissolve back through the Roman line and allow the more experienced soldiers in the Principes to fight. In turn, the Principes could yield to the hardened Triarii if necessary. The latter situation led to the Roman saying "ad triarios redisse", "to fall back on the Triarii", meaning that things had come to a desperate pass.  The maniples in each line generally formed with a one-maniple space between each (soldier) maniple and its neighbours, and the maniples in each of the forward lines covering the gaps in the line behind, so that retreating troops of the forward lines could withdraw without disrupting those behind them. Sources disagree on the numbers involved and in all likelihood they varied considerably but a generally accepted number is 20 maniples of Hastati and 20 of Principes of approximately 120 men each and 20 half strength maniples of "Triarii", for a total of 6,000 men.  The maniple typically consisted of 120 soldiers arrayed in three ranks of 40 men when engaged in battle (Primary sources for early Roman military organization includes the writings of Polybius and Livy). It was a formation to where the Romans could always rotate fresh men to the front to do battle and it was very effective as one of line of men could fall behind a fresh line of soldiers and visa versa.

The Roman Maniple Formation

  To Varro, it seemed that Hannibal had little room to maneuver and no means of retreat as his back was to the Aufidus River. Varro believed that when pressed hard by the Romans' superior numbers, the Carthaginians would fall back to the river and, with no room to maneuver, be destroyed in the panic. Bearing in mind that Hannibal's two previous victories were won by his trickery and ruse, Varro had sought an open battlefield. The field at Cannae was clear, where no hidden troops could be brought to bear in an ambush (Moreman, Douglas. "Cannae – A Deception that Keeps on Deceiving").

  Hannibal, on the other hand, had deployed his forces based on the particular fighting qualities of each unit, taking into consideration both their strengths and weaknesses (Cottrell, Leonard. Enemy of Rome).  He placed his Iberians and Gauls in the middle, alternating the ethnic composition across the front line, with himself at the front and center. Infantry from Punic Africa was on the wings at the very edge of his infantry line. These infantry were battle-hardened, remained cohesive and would attack the Roman flanks.  Hasdrubal led the Iberian and Gaulish cavalry on the left (south near the Aufidus River) of the Carthaginian army. By placing the flank of his army on the Aufidus River, Hannibal prevented this flank from being overlapped by the more numerous Romans. Hasdrubal had about 6,500 cavalry, and Hanno had 3,500 Numidians on the right.  

   Hannibal  intended that his cavalry, comprising mainly medium Hispanic cavalry andNumidian light horse, and positioned on the flanks, would defeat the weaker Roman cavalry and swing around to attack the Roman infantry from the rear as it pressed upon Hannibal's weakened center. His veteran African troops would then press in from the flanks at the crucial moment, and encircle the overextended Romans.

  The Romans were in front of the hill leading to Cannae and hemmed in on their right flank by the Aufidus River, so that their left flank was the only viable means of retreat (Bradford, E. Hannibal). In addition, the Carthaginian forces had maneuvered so that the Romans would face east. Not only would the morning sun shine low into the Romans' eyes, but also the southeasterly winds would blow sand and dust into their faces as they approached the battlefield (Dodge, Theodore. Hannibal). Hannibal's unique deployment of his army, based on his perception of the terrain and understanding of the capabilities of his troops, proved decisive.

   As the armies advanced on one another, Hannibal gradually extended the center of his line.  Polybius describes: "After thus drawing up his whole army in a straight line, he took the central companies of Hispanics and Celts and advanced with them, keeping the rest of them in contact with these companies, but gradually falling off, so as to produce a crescent-shaped formation, the line of the flanking companies growing thinner as it was prolonged, his object being to employ the Africans as a reserve force and to begin the action with the Hispanics and Celts." Polybius described the weak Carthaginian center as deployed in a crescent, curving out toward the Romans in the middle with the African troops on their flanks in echelon formation (“Internet Ancient History Sourcebook”).

The Echelon Formation

  An echelon formation is a military formation in which its units are arranged diagonally. Each unit is stationed behind and to the right (a "right echelon"), or behind and to the left ("left echelon"), of the unit ahead.  Hannibal capitalized on Varro’s egotism and drew him into a trap using an enveloping tactic that eliminated the Roman numerical superiority by shrinking the area where combat would occur.  Hannibal drew up his least reliable infantry in the center of the semicircle with the wings covered by the Gallic and Numidian horse.

  It is thought that the purpose of this formation was to break the forward momentum of the Roman infantry, and delay its advance before other developments allowed Hannibal to deploy his African infantry most effectively (Healy, Mark. Cannae: Hannibal Smashes Rome's Army).  While the majority of historians feel that Hannibal's action was deliberate, some have called this account fanciful. They claim that the actions of the day represent either the natural curvature that occurs when a broad front of infantry marches forward, or the bending back of the Carthaginian center from the shock action of meeting the heavily massed Roman center (Healy, Mark. Cannae: Hannibal Smashes Rome's Army).

The Battle of Cannae

  The Roman legions forced their way through Hannibal’s weak center, but the Libyan mercenaries on the wings swung around their advance menacing their flanks.  The onslaught of Hannibal’s cavalry was irresistible. The cavalry engaged in a fierce exchange on the flanks. Polybius described the Hispanic and Celtic horse dismounting in what he considers a barbarian method of fighting. When the Hispanic and Gauls got the upper hand, they cut down the Roman cavalry without giving quarter ("Internet Ancient History Sourcebook").

On the other flank, the Numidians engaged in a way that merely kept the Roman allied cavalry occupied. When the victorious Hispanic and Gallic cavalry came up, the allied cavalry broke and the Numidians pursued them off the field ("Internet Ancient History Sourcebook”).

  While the Carthaginians were in the process of defeating the cavalry, the mass of infantry on both sides advanced towards each other in the center of the field. The wind from the east blew dust in the Romans' faces and obscured their vision. While the wind was not a major factor, the dust that both armies created would have been potentially debilitating to sight (Dodge, Theodore. Hannibal).  Although it made seeing difficult, troops would still have been able to see others in the vicinity. The dust, however, was not the only psychological factor involved in battle. Because of the somewhat distant battle location, both sides had to fight with little sleep. The Romans faced another disadvantage caused by lack of proper hydration due to Hannibal's attack on the Roman encampment during the previous day. Furthermore, the massive number of troops would have led to an overwhelming amount of background noise. All of these psychological factors made battle especially difficult for the infantrymen (Daly, Gregory. Cannae: The Experience of Battle in the Second Punic War).

  Hannibal stood with his men in the weak center and held them to a controlled retreat. The crescent of Hispanic and Gallic troops buckled inwards as they gradually withdrew. Knowing the superiority of the Roman infantry, Hannibal had instructed his infantry to withdraw deliberately, creating an even tighter semicircle around the attacking Roman forces. By doing so, he had turned the strength of the Roman infantry into a weakness. 

While the front ranks were gradually advancing, the bulk of the Roman troops began to lose their cohesion, as they began crowding themselves into the growing gap. Soon they were compacted together so closely that they had little space to wield their weapons. In pressing so far forward in their desire to destroy the retreating and seemingly collapsing line of Hispanic and Gallic troops, the Romans had ignored (possibly due to the dust) the African troops that stood uncommitted on the projecting ends of this now-reversed crescent (Healy, Mark. Cannae: Hannibal Smashes Rome's Army).   This also gave the Carthaginian cavalry time to drive the Roman cavalry off on both flanks and attack the Roman center in the rear. The Roman infantry, now stripped of protection on both its flanks, formed a wedge that drove deeper and deeper into the Carthaginian semicircle, driving itself into an alley formed by the African infantry on the wings (Cottrell, Leonard. Enemy of Rome).   At this decisive point, Hannibal ordered his African infantry to turn inwards and advance against the Roman flanks, creating encirclement in one of the earliest known examples of a pincer movement.  The pincer movement typically occurs when opposing forces advance towards the center of an army that responds by moving its outside forces to the enemy's flanks to surround it.

Hannibal’s Pincer Movement

  When the Carthaginian cavalry attacked the Romans in the rear and the African flanking echelons assailed them on their right and left, the advance of the Roman infantry came to an abrupt halt. The Romans were now trapped 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” (Healy, Mark. Cannae: Hannibal Smashes Rome's Army).  

The Death of Consul Lucius Aemilius Paullus at Cannae

 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” (Livy. The History of Rome by Titus Livius: Books Nine to Twenty-Six, trans. D. Spillan and Cyrus Edmonds). Cowley claims that nearly six hundred legionaries were slaughtered each minute until darkness ended the bloodletting (Cowley, Robert (ed.), Parker, Geoffrey (ed.) The Reader's Companion to Military History, "Battle of Cannae"). Only 14,000 Roman troops managed to escape, most of whom had cut their way through to the nearby town of Canusium. Canusium (modern Canosa di Puglia) was a town in Apulia in southern Italy, between Bari and Foggia, not far from the position on the Aufidus River (Ofanto River) where the Roman soldiers found refuge after their defeat at the Battle of Cannae.

  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 (Polybius. The Histories, 3.117).  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." He also reports that 3,000 Roman and allied infantry and 1,500 Roman and allied cavalry were taken prisoner by the Carthaginians. 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 Livy names when reporting the casualties at the Battle of Trebia (Livy. The History of Rome by Titus Livius: Books Nine to Twenty-Six, trans. D. Spillan and Cyrus Edmonds). 

  In addition to the Consul Lucius Aemilius Paullus, Livy goes on to record that among the dead were two 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"(Livy. The History of Rome by Titus Livius: Books Nine to Twenty-Six, trans. D. Spillan and Cyrus Edmonds).  Some more recent historians have come up with far lower estimates. Cantalupi proposed Roman losses of 10,500 to 16,000 (Cantalupi, P. "Le Legioni Romane Nella Guerra d'Annibale"), 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 people  whom Hannibal hoped to win as allies (Samuels, M. "The Reality of Cannae”).  Later Roman and Greco-Roman historians largely follow Livy's figures. Appian gave 50,000 killed and "a great many" taken prisoner (Appian. Hannibalic War, 4.25).   Plutarch agreed, "50,000 Romans fell in that battle... 4,000 were taken alive"(Plutarch. Fabius Maximus, 16.8). Quintilian: "60,000 men were slain by Hannibal at Cannae"(Quintilian. Institutio Oratoria, 8.6.26.).  Eutropius: "20 officers of consular and praetorian rank, 30 senators, and 300 others of noble descent, were taken or slain, as well as 40,000 foot-soldiers, and 3,500 horse"(Eutropius. Abridgement of Roman History, 3.10).

  Livy recorded Hannibal's losses at "about 8,000 of his bravest men." (Livy. The History of Rome by Titus Livius: Books 9 to Twenty-Six, trans. D. Spillan and Cyrus Edmonds) Polybius reports 5,700 dead: 4,000 Gauls, 1,500 Spanish and Africans, and 200 cavalry (Polybius. The Histories, 3.117).

  “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 Lake 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 at Cannae (Livy. The History of Rome by Titus Livius: Books Nine to Twenty-Six, trans. D. Spillan and Cyrus Edmonds).

    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 had died that someone was related to or knew. 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 (Palmer, Robert EA (1997). Rome and Carthage at peace).

The two legions that survived Cannae were 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” (Gowen, Hilary. "Hannibal Barca and the Punic Wars).

   Hannibal had defeated the equivalent of eight consular armies (16 legions plus an equal number of allies) (Slip Knox, E.L. "The Punic Wars—Battle of Cannae"). 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 (Cottrell, Leonard. Enemy of Rome). Furthermore, the morale effect of this victory was such that most of southern Italy joined Hannibal's cause.