How did Scipio Africanus recruit his army for Zama?

Question

The story of the Second Punic War doesn't quite add up to me. According to Cottrell [1], after the battles at the Trebia, Trasimene, and Cannae, Hannibal had slaughtered in battle 1/5 of the Roman male population over 17 years of age. And in the ensuing years he spent campaigning in Italy, he didn't stop annihilating entire Roman armies -- he did it again at the Silarius and Herdonia. It's unclear who Cottrell is counting among the Roman population in his estimate, but it seems relevant that after Cannae there were significant defections of Roman cities to the Carthaginians, further shrinking the pool of manpower from which Roman generals could levy armies.

There must be something to say here about the sheer political will it took for Rome to continue resisting Hannibal through such adversity. The explanations given for why Hannibal never besieged the city of Rome really don't add up to me. And it seems incredible that in such conditions it was possible for the Romans under Scipio to launch a counter-invasion of Carthage. But for now I will content myself with a more specific logistical question:

Question: Who were the individuals who fought for the Romans under Scipio Africanus at the Battle of Zama? Where did Scipio find them, and how did he incentivize them to fight for him?

Since the adult male population of Rome was so heavily depleted through battle with Hannibal, I am wondering where Scipio found men to fight in his army (estimated at 36,000 men [2]). Was this a case similar to Germany near the end of World War II, where young boys and old men were being pressed into service?

[1] Cottrell, Leonard. Hannibal: Enemy Of Rome. Da Capo Press, 1992. p. 148

[2] op. cit., p. 235

Answer 1

I think part of the error here is in assuming that such losses would be sufficient to put a dent in Roman yearly recruitment. The spring of Cannae (216 BC) had actually been their best recruitment season of the war to that point, with 45,000 Roman and 45,000 allied troops recruited¹. 215 was obviously going to be a rebuilding year, but with the spur of possible imminent destruction on their doorstep, they still fielded 140,000 men. For the 214 campaign season they did even better, putting 200,000 men in the field (again, half Roman, half allied). About 30% of these troops were fresh recruits, the rest veterans from the previous year. In 213 the number inched even higher to 220,000.

This whole time Hannibal was not receiving much in the way of reinforcements, and being conspicuously bad at sieges of Italian cities. So from this time forward the writing was on the wall. Still even with forces nearly tripled, they couldn't destroy his army.

Clearly manpower for an invasion of North Africa was not going to be wanting, and perhaps limited only by Roman capacity to transport it there and keep it supplied. One would imagine their well-earned respect for Hannibal, who was still marching around their peninsula, also kept the numbers sent abroad down a bit.

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^{1 - I'm getting these numbers from my old copy of Dodge's Hannibal (originally published in 1891), but the numbers ultimately come from quoted sections of (I believe) Polybus.}

Answer 2

Publius Cornelius Scipio, who didn't acquire the Africanus until after the battle at Zama used strategies he had developed over time specifically to fight Hannibal. He took on board his errors and adapted. For example he used the same Numidian cavalry that Hannibal had used successfully for many years. The realty was Hannibal lost the battle well before it commenced.

Specific factors

Logistics As others have said for the Romans manpower nor supplies were an issue, for all intents and purposes it had an inexhaustible supply of both. It wasn't a question of Rome having an army, it was more an army having a wealthy state.

"Polybius, a keen observer of the Roman military at its height, remarked that “the advantages of the Romans lay in inexhaustible supplies of provisions and men.” The_Logistics_of_the_Roman_Army_at_War_(264BC_-_235AD J.P.Roth

Pre battle preparations Scipio took a large portion of Hannibal's troops out of the battle well before it commenced. In 203BC he killed around 40,000 Nubidians as a by product of his unsuccessful of the Siege of Utica, it was a lucky break but as they say some people make their own luck. The strategy Scipio used were classic Hannibalistic. Use of terrain, stealth, night manoeuvres, fierce fires to create panic and confusion.

"Forty thousand men perished either from the fire or the enemy, over 5000 were taken alive, including many Carthaginian nobles of whom eleven were senators; 174 standards were captured, 2700 horses and 6 elephants, 8 others having been killed or burnt to death. An enormous quantity of arms was secured, these the general devoted to Vulcan, and they were all burnt.Livy Book 30 vi

Diplomacy Scipio was a skilful diplomat, he was by all reports charming and gracious. Hannibal not so much. The Carthaginian senate confronted with Scipio, who by now had quite a few victories to his name outside their front door with a well supplied army in well fortified winter camp camp the Carthaginian senate it is reasonable to assume started discussing terms well before the battle behind the back of Hannibal.

"as winter was coming on he constructed an entrenched camp on a tongue of land which projected into the sea and was connected by a narrow isthmus with the mainland. He enclosed the military and naval camps within the same lines. The legions were stationed in the middle of the headland; the ships, which had been beached, and their crews occupied the northern side; the low ground on the south side was allotted to the cavalry. Such were the incidents in the African campaign down to the end of the autumn, Livy Book 29 xxxv

On the day Scipio tactics were brilliant. He used long thin lines perpendicular to Hannibal's elephants. As they charged past they were wounded with sharp lances and javlins. Trumpets and flags caused further confusion, some elephants ran amok among Hannibal's left hand ranks. Scipio used Numidian cavalry, the same one cavalry as Hannibal's and it was suggested this made the difference.

"In attack they charged with fiery £lan, but at once turned on meeting opposition ; not, however, to fly, for they charged again and again, riding up into the very teeth of the foe, but never remaining to fight hand to hand with heavier troops. As a curtain for the army in which they served, and as an element to unsettle the morale of the enemy, they ranked among the best of light horse. They were equally useful on level or broken terrain, and were peculiarly clever in taking advantage of the accidents of the ground for ambush or temporary defense. In pursuit they never tired, and here they were the most dangerous of opponents. Like our own broncos or the Cossack horses, their little nags were wonderful for endurance and activity, and throve on food which would kill a civilized horse. On the other hand, they were cruel, reckless and noted for plundering and rapacity. TA Dodge

"by far the best horsemen in Africa." Livy

the Romans allied with the Numidian king Masinissa who led 6000 horsemen against Hannibal's own in the battle of Zama, where the "Numidian Cavalry turned the scales" Fuller, J.F.C., Julius Caesar: Man, Soldier, and Tyrant. p. 28