In modern times, we think of military service as a temporary thing, a term of service lasting a few years before soldiers return to civilian life. Even in long wars, armies cycle soldiers constantly, replacing old, worn out men with fresh recruits. However, this was not always the case. During the ancient world, armies could spend years on foreign soil, hundreds of miles from home. The most extreme example of permanent military service was the army of the great Carthaginian general Hannibal during the Second Punic War. Hannibal’s army spent 15 years fighting the Roman Republic on Italian soil. The shocking length of Hannibal’s campaign raises all kinds of fascinating possibilities. By the end of the campaign, for instance, it is likely that more of Hannibal’s soldiers were dying from simple old age than from fighting Romans. 

In the winter of 218 BCE, Hannibal and his army marched from their base in Iberia, through the Alps, and into Italy. Historians differ on the size of Hannibal’s initial army. Polybius, our best semi-contemporary source, writes that Hannibal began his march with nearly 100,000 men, but over the course of the difficult journey, two-thirds of the men either died or deserted (including, famously, dozens of elephants). More recent historians, most notably Prussian historian Hans Delbrück, are skeptical of such apocalyptic casualties. Delbrück suggested that Hannibal began his march with about 36,000 men and only lost a couple of thousand on his journey through the Alps. Whichever account you believe, Hannibal arrived in Italy with about 35,000 troops, roughly half of whom were Iberian, and the other half from North Africa. 

Once in Italy, Hannibal recruited large numbers of Gauls from tribes of the Po River Valley, and with their help, defeated the Romans in many large battles. By the time of the climactic Battle of Cannae in 216 BCE (the last time we get a detailed layout of Hannibal’s forces) ancient historians gave Hannibal roughly 50,000 troops, consisting of 20,000 Gauls, 15,000 Iberians, and 15,000 North Africans.

After their crushing defeat at the battle of Cannae, the Romans adopted a strategy of avoiding contact with Hannibal’s army. For the next 13 (!) years, Hannibal and his army rampaged around Italy, unable to get reinforcements or come to grips with the Romans. The long Italian campaign ended in 203 BCE when Hannibal returned to North Africa to oppose a Roman attack on his homeland. Hannibal’s army was destroyed the next year at the Battle of Zama, effectively marking the end of the Second Punic War

The diversity of Hannibal’s army is a fascinating topic in its own right. Each of the three main groups of soldiers  – North Africans, Iberians, and Gauls, would have included many subgroups with different languages and ethnicities. Any one of those three collections of groups would have been a fantastically polyglot army, but the result of combining the three, Hannibal created perhaps the most diverse army the ancient world ever saw. 

Yet one of the most remarkable things about the army would have been the age of its members. Before Hannibal’s long campaign in Italy, his army was likely very diverse in age, and by the end of its decade and a half spent in Italy, Hannibal’s army was likely the most elderly army in world history. 

A Highly Speculative Estimate of the Average Age of Hannibal’s Soldiers

Historians don’t always have reliable information about the age of recruits in Classical Mediterranean armies, but the best source comes from Rome. In the Roman Republic, men between the ages of 16 and 45 were eligible for military service, but in practice most recruits were probably in their late teens or early twenties. Some readers might be surprised to see that the age of military recruitment hasn’t really changed in 2200 years, but there are good reasons for the consistency. Males reach their peak physical strength in their early twenties, and militaries usually prefer to recruit men in the golden zone between being mostly physically developed and not yet responsible for families. Such men are both up to the physical challenges of fighting and socially expendable. 

So if we accept an average age of recruitment of 20 (probably a conservative estimate given that a fair number would have been over 30), then the average birth year for the army’s Gallic recruits would be about 237 BCE, since most enlisted in 217 BCE. It’s more difficult to say when Hannibal’s Iberian soldiers were recruited. The Carthaginians had occupied and colonized parts of Iberia starting in 237 BCE, and would have constantly hired or conscripted Iberians between then and Hannibal’s expedition in 218 BCE. It seems plausible that many would have been raised by Hannibal in anticipation for his invasion of Rome in 218 BCE. Let’s put more weight on the latter number and estimate, once again rather conservatively, that the average Iberian recruit joined Hannibal’s army in 220 BCE, putting the average birth year at about 240 BCE.

Finally, we turn to the the North Africans. These would have been, on average, the oldest soldiers in Hannibal’s army, since they had to be enlist in North Africa, travel to Iberia, then march to Italy with Hannibal. As mentioned above, the first North African army had arrived in Iberia in 237 BCE, under the command of Hannibal’s father, Hamilcar. The ancient historian Diodorus Siculus puts the size of Hamilcar’s army at 20,000, almost all of whom would have been from North Africa. We know that Hannibal invaded Italy with 15,000 North Africans, and left few behind in Iberia, so it seems likely that a not insignificant proportion of Hannibal’s North Africans would be old veterans who have arrived in Iberia in 237 BCE. What’s more, these original North Africans would not have enlisted in 237 BCE, since Hamilcar had used the same army to fight in the Mercenary War, from 241-237 BCE. The sources make it clear that Hamilcar had to hire raw recruits at the start of the war, so we can fairly confidently put the average recruitment year of Hamilcar’s men at 241 BCE, which puts the average birth year at 261 BCE. 

Of course, not all of Hannibal’s North Africans in 218 BCE would have been his father’s veterans from 241. Reinforcements would have arrived and men would have retired in the intervening years. Hannibal’s North Africans, then,  would have ranged from an average birth year of 261 BCE (for Hamilcar’s old troops) to an average of maybe 247 BCE (for all the men arriving between 237 BCE and 218 BCE). If we accept the two groups were about equal in size (a big assumption, but since the Carthaginian Senate in North Africa had very hostile relations with Hannibal’s family in Iberia, and didn’t expect war in 218, there was unlikely to be a big pre-war buildup of North Africans in Hannibal’s army) then the average birth year for Hannibal’s North Africans would have been about 254 BCE, with considerable variance on either end. 

After completing our back-of-the-envelope calculations, we can conclude that Hannibal’s army at Cannae consisted of: 

20,000 Gauls, average birth year 237 BCE, with relatively little variance in age. 

15,000 Iberians, with average birth year 240 BCE, with moderate variance in age. 

15,000 North Africans, average birth year 254 BCE, with extreme variance in age. 

Looking at this figure, it seems clear that Hannibal’s army was not only the most ethnically diverse of the ancient world, it may also have been the most diverse in age. Many of Hannibal’s North Africans would have been fighting in Iberia before many of his Gauls were even born. 

The other remarkable thing about Hannibal’s army was the length of time it spent in the field. Between 217 and 203 BCE, Hannibal’s army stayed in southern Italy, burning the countryside and besieging cities, cut off from new recruits but too strong for the Romans to challenge in battle. Yet the army faced a terror more dangerous than any Roman: age. By the end, men in Hannibal’s army were, on average, probably one of the oldest in any large army in world history. 

Another Highly Speculative Model for Aging in Hannibal’s Army

It is a well known fact that life in the classical world was nasty, brutish, and short. Many estimates but the average lifespan at no more than 25-30 years. However, that number is deceptive because it assesses life expectancy at birth. Infant mortality rate in the ancient world was astronomical, which deflated the average enormously. The general scientific and archaeological consensus is that if a person survived to adulthood in the ancient world, they could expect to live to an average age of 45-55. 

Age and natural causes would have reaped a huge toll on Hannibal’s army in Italy. By 203 BCE, when the army returned to Africa, the average age of Hannibal’s Gauls would have been 34, the average age of his Iberians would be 37, and the average age of his North Africans would have been an incredible 51! If you take the troop ratios and average ages from the calculations above, the average soldier would have been about 40 years old by 203 BCE. The real averages would, of course, have been somewhat lower, because inevitably, many of the older men would have died. 

Given that life expectancy varies by person, and that we’re dealing with variance in Hannibal’s army (as discussed earlier, the birth date of Hannibal’s north Africans would have varied by a span of more than twenty years), these numbers are very rough estimates, but we can construct a model of age-related mortality in Hannibal’s army. 

In addition to knowing the average life expectancy, we have to know the variance of life expectancy. It’s impossible to know the variance of life expectancy among the general population, but studies of famous people in pre-modern times gives a consistent standard deviation of about 15 years, which has remained fairly constant through history even as lifespans have lengthened. This is an imperfect measure, but if we combine it with our average adult life expectancy, we get the following rough estimates. 

13.5% of men who survive to adulthood die between ages 20 and 35

34% die between ages 35 and 50 

34% die between ages 50 and 65

13.5% die between ages 65 and 80

Note: I encourage people to examine Dr. Bruce Frier’s model of life expectancy during the Roman Empire. While his methodology is far more sophisticated than mine, his estimates of male life expectancy are surprisingly similar to the ones outlined above. 

When Hannibal returned to North Africa in 203 BCE, historians guess his army numbered between 10,000 and 15,000 men. Such numbers may seem surprising, given that between 216 and 203 BCE the army had fought in only a handful of small battles, and in many years had no contact with the Romans at all, yet in the same period the army had lost around three-quarters of its strength. Yet the decline in Hannibal’s army makes a great deal more sense when you consider the age of the participants. Perhaps as many as half of Hannibal’s North African soldiers might have died from simple non-combat factors like epidemics, accidents, or even more mundane causes like heart conditions or cancer. Significant numbers of Gauls and Iberians would have suffered similar fates. I know of no other historical example of “waiting for the enemy to die of old age” being an effective (perhaps even war-winning) tactic. 

By the end, Hannibal’s army may well have been among the grayest armies in world history. In the 20th and 21st century, the vast majority of soldiers have ranged from 20-25 years old. If the tombstones and records from Imperial Roman legions are anything to judge by, the same was true for armies in antiquity as well. And while it is certainly not unusual to see older soldiers, particularly officers, I can think of no other example of an army where virtually every man, from cesspit cleaner to general, was over the age of thirty, and many would have been far older. 

The shocking duration of Hannibal’s Italian campaign conjures up many other strange and interesting possibilities. Typically, pre-modern armies contained not only men but a large number of women and children who helped the army operate. It is entirely plausible, then, that a newborn Iberian child who crossed the Alps with his family in 218 BC would have grown up with the army and eventually fought alongside his father in the 202 Battle of Zama. Another fascinating yet unanswerable question is how the language of the army developed. The army was split three ways between Gallic, Iberian, and North African languages and cultures, yet over the course of 15 years, the army must have seen immense linguistic and cultural mixing. It’s not hard to imagine a kind of pidgin language emerging, combining words from the army’s many tongues. 

Another interesting question is how age would have affected the combat ability of Hannibal’s soldiers.  some of the most experienced soldiers the ancient world ever saw. Undoubtedly, Hannibal’s soldiers were some of the most experienced the ancient world ever saw, and they would have enjoyed an unparalleled level of trust in each other and their officers. But other factors may have made Hannibal’s men less effective than one might think. Military researchers have determined that in modern conflicts, the effectiveness of a soldier increases as he or she gains more experience. Once the soldier reaches a certain peak, however, military effectiveness gradually declines. The reasons for this likely have something to do with a soldier’s belief that they’ve “done their bit” and have nothing more to prove. It might also have something to do with the fact that more aggressive and brave soldiers are the most likely to die. Imagine the position of one of Hannibal’s soldiers after ten years in Italy. Would you really feel particularly inclined to risk your life in yet another fight? 

Add in the physical deterioration the men would have felt as they aged (even the youngest Gallic recruit would have been over thirty by the end) and you might reasonably speculate that Hannibal’s veterans were not quite the supersoldiers one might expect. That said, they were clearly still capable – ancient historians make it clear that at the 202 BCE Battle of Zama, Hannibal’s old veterans still put up a hell of a fight. 

Long wars were not uncommon in the ancient world. The First Punic War, for example, lasted from 264 to 241 BCE, a full 23 years. But for most of these conflicts, armies received constant opportunities for both recruitment and retirement. The Second Punic War special because Hannibal’s army was truly alone, far from any friendly population centers. I have to wonder how Hannibal’s men felt about being utterly separated from civilian life for half a lifetime, with no knowledge of the people on whose behalf they were fighting the war. Whatever the emotions of the men were, there can be no doubt that Hannibal’s army was one of the most unique of all antiquity.