Hannibal in the Alps

There are two ancient texts that give a description of Hannibal's route. The oldest is in the third book of the World History by the Greek historian Polybius of Megalopolis (ca.200-118 BCE). At first sight, this text seems to describe a rather northerly route, because it mentions a Celtic tribe, the Allobroges, which lived on the banks of the river Isère in the second century BCE. The other source is the twenty-first book of the History of Rome from its Foundation, written by Polybius' Roman colleague Titus Livius of Padua, better known to English readers as Livy (59 BCE-17 CE). He suggests a more southerly route. Both texts can be found here.

Livy and Polybius indirectly used the same eyewitness account. This may have been written by one of Hannibal's companions, Sosylus of Lacedaemon, who is known to have written a history of the Second Punic War in seven books. Polybius used the original text; Livy knew it indirectly. His real source cannot be identified, but we can be confident that this intermediary was a careful author, who meticulously copied all the chronological indications he found in the eyewitness report. He also added explanations; that these are correct can not be known, but Livy's chronology is precise:

Another approach of the problem is to look at the passes in the Alps, and to find out which one suits the texts best. From north to south, these passes are:

1. Col du Petit Saint Bernard
• from modern Bourg St Maurice and La Rosière to La Thuile and Aosta (N90 and SS26);
• advocated by Barthold Niebuhr, Theodor Mommsen, Lehmann, Viedebrandt, H. Kiepert and Francis de Conninck.
2. Mont Cenis
• from modern Bramans and Val Cenis to Bar Cenisio and Susa (N6 and SP212);
• advocated by Napoleon Bonaparte, H. Nissen, D. Procter.
3. Col du Clapier
• from modern Bramans and Le Planay to Grange Buttigliera and Susa;
• advocated by Perrin, P. Azan, Collins, Wilkinson, and Serge Lancel.
4. Col du Montgenèvre
• from modern Briançon and Montgenèvre to Cesana Torinese and Oulx (N94 and SS24);
• advocated by Neumann, Fuchs, Gaetano de Sanctis and Peter Connolly.
5. Col de la Croix
• from modern Abriès and l'Echalp to Pra Miraflores and Pinerolo.
6. Col de la Traversette
• from modern Abriès and l'Echalp to Pian del re and Saluzzo;
• advocated by Sir Gavin de Beer, A. Guilleaume, and J. Prevas.

1. The pass has to offer sufficient room to build a camp for at least 20,000 soldiers, 6,000 cavalry and twenty-seven elephants (the number of men that would reach Italy);
2. The defile should begin within 15 to 30 kilometers from the summit, because Hannibal's soldiers started to climb down on the day they left the camp on the summit;
3. The road to Italy must be in a northerly direction: the soldiers encountered snows of the previous year when they were descending;
4. The first part of the descent has to be narrow and steep;
5. After this, the descent has to be less steep for about 50 kilometers, because it took Hannibal's men three days to reach the plain;
6. Italy should be visible from the summit (according to Polybius) or from a point at the beginning of the precipitous descent (according to Livy), because Hannibal was able to show his men the plain during a speech.

Now that we know that Hannibal crossed the Alps between Briançon and Susa, we can try to find the other stations of his march. The enemy town that was taken on the third day, can easily be identified with modern Gap, because it is a three days' march downstream from Briançon (i.e., days four, five and six). The fort captured by Hannibal's men must be the Mont Saint-Mens (ancient Vapincum), immediately south of the modern town. 

It is harder to establish the route during the first days. Livy states that Hannibal started his march on the banks of a river called Druentia; this cannot be the Durance, because it is too southerly. The Drôme and Isère are possible, and the first one should be preferred because in that case the distance to Gap can be covered in two or three days. The pass which Hannibal took during the second night, can be identified with the Col de Cabre.

(The argument that Hannibal encountered the Allobroges and consequently must have passed along the Isère is not conclusive, because Celtic tribes were not very sedentary. The fact that the Allobroges lived on the banks of the Isère in the second century BCE does not prove that this was their home in the third century.)

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