Fantastic question, and it'll require a bit of an explanation of the Roman army of that period! The great news is that I was JUST talking about this with a friend of mine and she pointed out that you'd asked this question. Many of our sources discussing the training of the Roman military come from centuries later than this time period, so this is a bit of a trickier question than you might think. Also, well....the Roman army during the Punic Wars wasn't exactly the army which is envisaged when you say "legionary." The better news? I've actually answered a very similar question to this before :) I'll copy and paste for convenience.

THE PUNIC WARS (264 BCE -146 BCE with some intermissions) - For further reading on this era, check out Goldsworthy's "The Fall of Carthage" and O'Connell's "The Ghosts of Cannae". "The Complete Roman Army" has some good stuff as well here.

Many of you reading this know the basic story of the Punic Wars - or at least the second one, where you have Hannibal plowing across the Alps and promptly stomping through back-to-back Roman armies on the Italian peninsula. He was constantly outnumbered, and yet he smashed the Roman armies at Trebia, drowned them in Lake Trasimene, and utterly dominated them at Cannae. He never lost a battle on the Italian peninsula, and the road behind him was scattered with Italian soldiers. A narrative that's also known, albeit a bit less, is that Rome lost significantly more men in the First Punic War than Carthage did, despite winning most of their battles on land and sea - unless bad weather was involved. Even in the Third Punic War, the Romans had an incredibly massive army. That army was also known for its lack of discipline and relatively poor performance. Why?

The Roman army in this era was one of the most dominant armies in the history of the Republic. Interestingly enough, they're also easily ranked among the best militias in the world. The army was a militia force - even when you get to the 80,000 man army used at Cannae - and it was raised on a yearly basis. The Senate would decide how many men were needed and where. Each of the two consuls (chief magistrate - think of them as general-presidents in this context. They were co-commanders-in-chief, but they were expected to actually lead their armies themselves) would be assigned a number of legions depending on Rome's need, and the size of those legions, again, would depend on Rome's need. In a time of relative peace, the legions would number about 4,200 infantry and 300 cavalry each, while when the Republic was in danger (Hannibal), we have records of legions being numbered at about 6,000 infantry each. These legions would be levied from the landholders of Rome. Basically, they were farmers.

Those farmers were expected, when they came of age, to serve proudly in the Roman army when the need required. How long they stayed evolved over the course of the Punic Wars quite drastically - the "Cannae Legions," for example, served longer than any other Romans at that point in history, and I'll get to them in just a bit - but the basic expectation of each man would be that they served 16 campaigns before they were no longer eligible for service. That's basically at least 16 years of warfare, which would suggest that they were far more capable in warfare than most of them were.

The thing is, though, Romans in this period identified extremely closely with Rome herself, and it was considered an extremely high honour to submit to Rome's intense discipline and fight in her honour. Mustering for the army was done on the Campus Martius - the Field of Mars - right outside the City, and those were were selected/drafted would go straight into the army. Politicians were in charge of the army as a whole, but there was no real "boot camp" that was specified for any legion. Up top, you had your consul (or praetor, if it was a small operation that only required one legion), and in charge of each legion, you had your military tribunes (who were also elected officials). So how about the centurions, you ask? Well, you military folks here will have a chuckle at this one. The centurions were elected by the soldiers. While in theory, this would mean that the most experienced men would be officers, experience and ability weren't necessarily the prime qualifications for election.

That leads straight into why the legions facing Hannibal performed so poorly to begin with. While they had the numbers, and while their commanders were certainly relatively experienced men, the men themselves were, although disciplined, extremely poorly trained. As such, they were unable to execute any maneuvers beyond the basics (manipular formation), and were subsequently extremely predictable. There was little to no unit cohesion, and even the more experienced men had not fought as a unit before. That cohesion takes time to build, as Rome later practiced, and, while their discipline (building camps and extremely harsh punishments) kept their men in line, formal training was nonexistent. If a commander wanted to train his men, he could be accused of dallying - an incredibly sharp political attack - or would lose most of his campaign season. Roman magistrates were only supposed to occupy their office for one year, which meant that they just didn't have any time to train their men. They had to take what they had and go, counting on their morale, discipline, and numbers to brute force their way through opposition. Scarily, it worked more often than not.

Then again, there were times where it just didn't. When Hannibal barged in on the Italian Peninsula, he had an army of veterans who had fought for most of their lives in Spain. They were the same men who had fought with each other the entire time, and they were extraordinarily experienced in combat. The ones who survived the crossing of the Alps were the hardest core of THAT force. So just starting off, he had an incredibly strong foundation to work with, and that foundation was responsible for the most infamous defeats in Roman history. Even if weather killed more Romans in the First Punic War than Hannibal did in those three battles. The Romans needed a solution, and badly, though they refused to budge on many of their values. After Cannae, there were about 8-12,000 survivors who were able to get out of Hannibal's trap. Those men were promptly sent to Sicily, effectively being exiled, to fight down there. And fight they did, until they were recruited for Scipio's African campaign over a dozen years later.

Magistrates in this time began to be appointed for years past their "expiration date." They were called "proconsuls" or "propraetors" (effectively the same thing), and were given command in a given province for years at a time. With that expanded time frame, many commanders, such as Scipio Africanus, seized the opportunity to train their men extensively. Starting off, Scipio took command in Spain, where he was able to take over the remnants of his father's army, who had been fighting together for many years previously. Scipio headed over in the early winter, using that time to train his men and plan for his future campaigns. Those few months of training paid off handsomely, as he was able to promptly take New Carthage, giving his troops a huge degree of trust in their young commander. For the next four years, he fought tooth and nail up and down the Spanish peninsula, and that army under his command just became stronger the longer time went on. While they didn't have a conventional "boot camp," they went through a trial by fire, learning their stuff by experience. His centurions were still elected, but he was able to execute incredible maneuvers which caught his opponents completely off guard, and his men were stronger than any other Roman army on the field.

When Scipio headed down to Africa, same deal - except that the African legions had been in service even longer than the Spanish legions. They were forced to head down to Sicily after they survived Cannae - losing their status as "green troops" after that massacre - and they spent the next 12 years fighting up and down the length of the island. Other survivors of lost battles were filtered in to buffer their ranks, and by the time Scipio took control, they were 12,000 of the hardest veterans Rome had ever known, and they wanted revenge on Carthage.

Over time, however, Rome's armies lost their professional sheen. In the next few decades, men became harder and harder to find, and the armies that were mustered essentially rested on the laurels of their forefathers. Defeats followed, and yet the armies continued their downward spiral due to the Romans refusing to learn from Scipio Africanus' policy. Scipio Aemelianus, responsible for the razing of Carthage, came in to command an army which had besieged a disarmed city for 5 years without being able to take it. The army was incredibly undisciplined, demoralized, and lacked all of the positive traits of Africanus' legendary legions.

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Continued in the next post