Hannibal Crosses the Alps
A Route Examined and
a Proposed Alternate Route

Hannibal's Line of March Considerations:
Proposing a Route

By Russ Lockwood

Methodology

After reading multiple books about Hannibal's crossing of the Alps, one aspect comes to the fore: a host of military officers, scholars, and historians cannot agree on the route. The salient points--Rhone crossing, the Island, the Ascent spot, and the Pass--receive a considerable number of words and often cunning interpretations of the ancient histories, but at the core, they do not agree where these places are located.

This leaves two conclusions: since these esteemed authors cannot agree, another route might just be the real one; and, until we find a hundred frozen Carthaginians and pack animals at the bottom of a glacier-filled crevice, all routes must remain in play. With this in mind, I offer a different route, and perhaps a more interesting route than those offered by other authors, and dare I say, perhaps even the "right" route that Hannibal took on his way from Spain to Italy.

I started with Polybius and Livy, mixed in a goodly number of contrasting authors' ideas, and added my own secret ingredients: a dose of Carthaginian intention, examined maps, and spritz of what previous authors ignored, or at least did not examine or explain.

Considerations of a Trek

Guides

Hannibal was a clever commander, but not omniscient. Although he had a general knowledge of terrain, he didn't know the terrain exactly. He needed guides, and trustful ones at that. Foremost was "Magilus and other Celtic chieftains who had come to him from the plains of the Po" [Polybius III, 44]. Indeed, Hannibal and the chiefs gave a speech to his troops after crossing the Rhone, which was reported to encourage the troops with "confidence they could feel in the promises of the Gauls to guide them by a route on which they would be abundantly supplied and which would lead them rapidly and safely to Italy." [Polybius III, 44].

In effect, Hannibal was putting the fate of his Alpine-bound army in the hands of these Gallic guides, who, as Hannibal may have melodramatically noted while pointing at Magilus and friends, "If a small party can cross them, surely an army can." [Livy, XXI, 30]

Hannibal prepared as much as possible for the march, and had "thoroughly informed himself concerning the fertility of the regions at the foot of the Alps and near the River Po, the density of the population, the bravery of its men in war, and above all their hatred of Rome." [Polybius III, 34]. His returning envoys said the passage was difficult but not impossible and the tribes were "ready to cooperate and eager for his arrival." [Polybius III, 34].

So, to Hannibal, the army was ready to march, the tribes ready to let it through, and lots of warriors were ready to join it in Italy.

Navigation, Distance, and Time

Hannibal had a route picked out by his guides, although which one, we don't know any more than the actual one he took. But the original route was likely to be easier than his famous one, and with the idea that Hannibal prepared well, and with certain other clues in Polybius and Livy, it must have been south of his actual one. And, being a competent commander, he must have had a backup plan, too.

The questions become, how fast could Hannibal move an army from Spain to Italy? And what type of surprise could be achieved? His entire march was 8400 stades (1473km) from New Carthage to the Po Valley, of which 2600 stades (456km) was between New Carthage and the Ebro River, leaving 5800 stades (1017km).

But this route distance provided by Polybius includes what amounts to a detour north. The actual distance planned was probably less, and through, if not friendly, then at least neutral, territory. If Hannibal figured he could cover a modest 10km per day, and the original planned route was shorter than the actual one taken Polybius described, then you're looking at about three months time, and perhaps, should Hannibal march at 15km per day through alledgedly friendly territory, about two months.

Now, the distances cited by Polybius are very generic and obviously rounded off to the nearest hundred, yet since he had actually visited the region and the modern day distances reasonably tally, we can be reasonably sure of the accuracy. He puts great store in Roman measurements of the Via Domitia, and therein lies a descrepancy between his straight 8 stades to the mile versus 8.33 as others have claimed.

In any case, without GPS, the actual distances, rates, and other numbers will vary, or in determining them, we figure they might in a straight line "as the crow flies." But that if you're looking for a specific distance, then Polybius' numbers are a reasonable guide in themselves.

Hannibal knew that Massilia was allied to Rome, and this city on the sea was the biggest obstacle to go around in order to reach Italy. Its military forces was not much more than a garrison and would present no problems in the field, so Hannibal could discount a Massiliot army marching forth and blocking the way--scattered groups perhaps, but nothing that would halt or hinder an army. Likewise, he was not going to spend time capturing the place. Saguntum had required eight months to capture and Massilia would probably require additional time--especially since Rome commanded the sea and could easily re-inforce it.

However, scouts from Masssilia could easily detect a Carthaginian army and pass word to Rome, so the route planned would have bypassed the city in a wide arc in the hopes that it would slip by undetected. However, Hannibal understood that word would reach Roman ears sooner or later, and given the number of towns along the route of march between the Ebro River and Massilia, the alarm would have already been given. Yet, it is one thing for Rome to be aware that a war started with an army on the Ebro River, and another to know about a hostile army at Massilia.

To take a step back to 220BC, Hannibal knew, based on a warning previously delivered by Roman envoys, that Rome would go to war over Saguntum. If he sieged Saguntum, he had to figure on how long before word reached Rome and whether they would respond before it fell. At this point, in winter quarters, he did not know about a Roman response, but he learned that the Romans were taking on the Illyrians in a war in 219BC.

Polybius notes that a Roman army under Lucius Aemillius had been sent to Illyria "just before the summer in the first year of the 140th Olympiad," [Polybius III, 16] corresponding to 219BC. Saguntum fell under siege "at the same time" [Polybius III, 17] in the opening of campaigning season 219BC. The timing is uncanny. It also meant the Romans would be occupied elsewhere, leaving Hannibal a free hand. In any case, the city fell to Hannibal after an eight-month siege.

If April or May is the opening of campaign season, then the city fell in November or December, and Hannibal sent his troops into winter quarters. When news reached Rome, the response was immediate: they sent an embassy under Fabius post haste [Polybius III, 20] to Carthage with an ultimatum. Rejected, Fabius and the envoys return with news of war, and Carthage's backing of Hannibal's actions reached Hannibal's ears while he was still in winter quarters, quite possibly as early as March of 218BC, though likely later, just before he set out for Italy.

Which brings in the time of the Pleiades. Take your pick of what day it was:

    Pliny (1st C. AD): Nov. 6.
    Euctemon (5th C. BC): Nov. 7
    Geminus (1st C. AD): Nov. 7
    Callipus (4th C. BC): Nov 8
    Eudoxus (4th C. BC): Nov. 11

Whichever you pick, "nearing the time of the setting of the Pleiades" meant anywhere from mid October to early November. That means five months of marching started in mid May to early June. Working backwards gives you a crossing of the Rhone sometime from mid September to early October. Working backwards again suggests that Hannibal spent three months moving 3200 stades (561km) in between the Ebro River and Rhone River.

So, Hannibal knew the Romans were at war and would dispatch an army. The question then comes round again, where would a Roman army likely be? Two Roman consular armies were being readied: one under Publius Cornelius Scipio for Spain and another under Tiberius Sempronius Longus for Africa. Roman armies armies could march with the speed of the best of them, and they had the additional advantage of naval superiority.

Hannibal probably did not know exactly when a Roman army would set out for Spain, but he had a knowledge of mustering timetables and marching rates. Scipio's army actually sailed for Spain in the summer of 218BC, probably August. Depending on how well Hannibal knew--or guessed--about Roman procedures, the August timeframe, or perhaps even hedging into July, figured into his timetable. In plotting the two armies, much depended on the friendliness of the Celts on the way to Italy. Could he reach Massilia ahead of a blocking Roman army?

If Hannibal left in mid May, and if he figured a two or three month march to Italy, then the answer is yes. Indeed, with this timetable, Hannibal would reach Italy in July, crossing the Alps in summer, and still have a period of time for operations against any Roman army heading towards Spain. A month's delay still might work and he may have figured to squeak just ahead of any Roman army. Any more delays would mean crossing later in the year. And if Rome moved faster than expected, what was "Plan B," his back-up route?

On the Roman side, no doubt the consuls were doing their own calculations about time, distance, and troops. They must have figured that Hannibal could not reach the Rhone until marching through northern Spain to the Pyrenees and then across the mountains through a hostile western half of Gaul. Evidently, the thought of a Carthaginian army marching towards Italy presented no large problem, judging from the cavalier way they offered an ultimatum and then accepted war.

The Romans would send out two consular armies of two legions each, one under Sempronius and the other under Scipio. Sempronius received the Africa appointment and headed south. Scipio received the Spain appointment and headed north. Considering the losses the Romans took from Gallic tribes, the consuls figured that a consular army based around the friendly city of Massilia and maybe an allied tribe or two more would be able to hold off any assault until Sempronius crossed over to Africa and stormed Carthage.

Remember, Scipio, Sempronius, and the Senate had no idea of Hannibal's qualities other than Saguntum took eight months to capture. And if Carthage did create a large army, much of it would be whittled down by the time--and it would take time--it reached the Massilia area.

Hannibal, in thinking about Rome, probably deduced that the Romans would try to advance into Gaul and stop him before he reached Italy. Hence, when he looked at the timetable, he figured he had to be in a certain area at a certain time, for he was going to do an end around. He probably figured it unlikely that a Carthaginian Army could march next to Massilia and into Rome via the coastal road without a battle. To take the war to Italy, he had to be in Italy, and thus he sent for guides for another route--the Way of Hercules through the Alps.

He also knew he had to reach the Alps before they were closed for the winter. And he also knew that an Alps passage would be arduous. He knew that he must not find a fresh Roman army drawn up on the plains awaiting a presumably bedraggled force staggering out of some Alpine pass. And he knew that to fight a Roman army, even if successful, in Gaul would be to delay a crossing into Italy.

Hannibal's timing ultimately worked out, in that a Roman army conveniently moved out of Italy and into Gaul as the Carthaginian army slipped away and crossed the Alps into Italy. Even a few days delay--from battle or withdrawal--would have made an already difficult late-autumn/early winter crossing perhaps impossible. As it was, Hannibal took serious losses without a major battle with the Romans. How many fewer soldiers would have alit into Italy had a battle been fought at the Rhone? From the Rhone to the crossing of the Alps cost Hannibal half his army. Any fewer from a battle against a Roman consular army and there wouldn't have been enough to launch an offensive into Italy.

Marching Rates

How fast can an army march through friendly and hostile country? If you take overall numbers, Hannibal marched 8400 stades (1473km) from New Carthage to the Po Valley in five months, or about 10km per day. A four day march of 600 stades (105km) from the Rhone crossing to the Island works out to 26km per day. Under the protection of Brancus, the army moved 800 stades in 10 days, or 14km per day, over mostly open ground. The crossing of the Alps, 1200 stades (211km) took 15 days, or 14km per day.

One question arises: are these accurate? On the first impression, why not? Polybius recorded it. It must be. But, is it? Ancient historians tend to overstate numbers, in part to convey how difficult the challenge was to defeat such tough and numerous enemies. Yet Polybius' devotion to facts, his interviews with surviving veterans, and efforts at visiting locales argue in favor of accepting his version.

Still, he makes mistakes, or at least vague generalizations, notably the geography of the Rhone River. For example, he says the river runs southwest from the northern face of the Alps beyond the headlands of the Adriatic. Since he believed the Alps to run east and west, you'd think he would have said the river runs west, not southwest (otherwise, the river would run through the Alps). He may have meant in a more southwesterly direction to follow the contours of the Alps, but that's not what he wrote. So, if he careless here, he may be careless elsewhere, say, in distances. We can probably rely on Polybius' numbers, but not with the same accuracy as a GPS unit.

And what about marching distances per day? The entire five-month march averaged about 10km per day. Specific numbers in Polybius note 14km per day. Other places might hit 26km in a day. Hanno and the out flanking force apparently traveled 35km in a day. In another spot, the troops could not move through a defile in an entire night. Just how fast can you move 50,000 troops? And how far can you move them before they lose combat ability?

It should be noted that Delbruck, in his Warfare in Antiquity, contends that Hannibal started on his trek with 36,000 men, losing only 2,000 from the crossing of the Ebro to the descent onto the plains of Italy. He also points out a descrepancy of 8,000 "logchophoroi" ("lance-bearers" or peltasts) may not have been included in Polybius' figures--because tallies of what came over the Alps and what ended up fighting the Romans at Cannae are at loggerheads. Delbruck contends that large losses in Gaul were illusory and the numbers quoted by Polybius overstated.

In any case, much depends on what drives the troops. The 35km per day was for a light strike force whereas the 14km was for the entire army. In concentrated bursts, the army might be able to move faster than the 14km average, perhaps 20km per day. Anything higher and the army runs the risk of straggling, and Hannibal could not afford such attrition in relatively hostile country. If you tend towards the lower amounts, you will not go wrong.

The other point on marching speed concerns the route. A coast road is one thing, but turning at the Rhone towards the interior is another. Small obstructions can create big problems for an army on the march, especially when you're talking about tens of thousands of troops.

The rate an army moves remains open to speculation, but while hand-picked troops might be able to cover considerable distance in a single day, the bulk of the army does not. There is a tendency to overestimate numbers and distances in order to make the enemy seem tougher to defeat, and thus, increase the glory on the side of the underdog winners. Given the rounded numbers and martial favor of the victors' historians, a more conservative outlook is prudent when considering such figures.

Hannibal Crosses the Alps A Route Examined and a Proposed Alternate Route

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