Little certainty exists on the route of Hannibal's march through the mountains, and precisely which valleys and passes he used remains contested by historians.
The events recorded in ancient accounts and their relationship to the Alpine geography has been a matter of historiographical dispute since the decades following the Second Punic War.
Identification of the pass - the highest point of Hannibal's route and the beginning of his descent - that Hannibal took through the Alpine range determines which route his army followed.

Proposals have been made for the following passes: 
Little St Bernard Pass
Col de Clapier
Col de la Traversette
Col de Montgenèvre
The pass near Mont Cenis
Theodore Ayrault Dodge, writing in the late nineteenth century, argued that Hannibal used the Little St Bernard Pass, but modern historian John Francis Lazenby concluded that Col de Clapier was the pass used by Hannibal.
More recently, W. C. Mahaney has argued Col de la Traversette closest fits the records of ancient authors.
Biostratigraphic archaeological data has reinforced the case for Col de la Traversette; analysis of peat bogs near watercourses on both sides of the pass's summit showed that the ground was heavily disturbed "by thousands, perhaps tens of thousands, of animals and humans" and that the soil bore traces of unique levels of Clostridia bacteria associated with the digestive tract of horses and mules.
Radiocarbon dating secured dates of 2168BP or c.218BC, the year of Hannibal's march.
Mahaney et al.
have concluded that this and other evidence strongly supports the Col de la Traversette as being the 'Hannibalic Route' as had been argued by Gavin de Beer in 1974.
De Beer was one of only three interpreters - the others being John Lazenby and Jakob Seibert de. -
to have visited all the Alpine high passes and presented a view on which was most plausible.
Both De Beer and Siebert had selected the Col de la Traversette as the one most closely matching the ancient descriptions.
Polybius wrote that Hannibal had crossed the highest of the Alpine passes: Col de la Traversette, between the upper Guil valley and the upper Po river is the highest pass.
It is moreover the most southerly, as Varro in his De re rustica relates, agreeing that Hannibal's Pass was the highest in Western Alps and the most southerly.
Mahaney et al.
argue that factors used by De Beer to support Col de la Traversette including "gauging ancient place names against modern, close scrutiny of times of flood in major rivers and distant viewing of the Po plains" taken together with "massive radiocarbon and microbiological and parasitical evidence" from the alluvial sediments either side of the pass furnish "supporting evidence, proof if you will" that Hannibal's invasion went that way.

According to historian Theodore Ayrault Dodge, Hannibal marched in the direction of Mt. Du Chat towards the village of Aquste and from there to Chevelu, to the pass by Mt. Du Chat.
There he found that the passes were fortified by the Allobroges.
He sent out spies to ascertain if there was any weakness in their disposition.
These spies found that the barbarians only maintained their position at the camp during the day, and left their fortified position at night.
In order to make the Allobroges believe that he did not deem a night assault prudent, he ordered that as many camp-fires be lit as possible, in order to induce them into believing that he was settling down before their encampment along the mountains.
However, once they left their fortifications, he led his best troops up to their fortifications and seized control of the pass.

Hiding his men in the mountain brush on a cliff that arose immediately above and to the right off Hannibal's route of march, about 100 feet or so above the path, Hannibal stationed his slingers and archers there.
This overhang was an excellent place from which to attack an enemy while it was marching in column through the pass.
The descent from this pass was steep, and the Carthaginians were having a hard time marching down this side of the pass, especially the bagg
Little certainty exists on the route of Hannibal's march through the mountains, and precisely which valleys and passes he used remains contested by historians. The events recorded in ancient accounts and their relationship to the Alpine geography has been a matter of historiographical dispute since the decades following the Second Punic War. Identification of the pass - the highest point of Hannibal's route and the beginning of his descent - that Hannibal took through the Alpine range determines which route his army followed.
Proposals have been made for the following passes: 
Little St Bernard Pass
Col de Clapier
Col de la Traversette
Col de Montgenèvre
The pass near Mont Cenis
Theodore Ayrault Dodge, writing in the late nineteenth century, argued that Hannibal used the Little St Bernard Pass, but modern historian John Francis Lazenby concluded that Col de Clapier was the pass used by Hannibal. More recently, W. C. Mahaney has argued Col de la Traversette closest fits the records of ancient authors. Biostratigraphic archaeological data has reinforced the case for Col de la Traversette; analysis of peat bogs near watercourses on both sides of the pass's summit showed that the ground was heavily disturbed "by thousands, perhaps tens of thousands, of animals and humans" and that the soil bore traces of unique levels of Clostridia bacteria associated with the digestive tract of horses and mules. Radiocarbon dating secured dates of 2168BP or c.218BC, the year of Hannibal's march. Mahaney et al. have concluded that this and other evidence strongly supports the Col de la Traversette as being the 'Hannibalic Route' as had been argued by Gavin de Beer in 1974. De Beer was one of only three interpreters - the others being John Lazenby and Jakob Seibert de. - to have visited all the Alpine high passes and presented a view on which was most plausible. Both De Beer and Siebert had selected the Col de la Traversette as the one most closely matching the ancient descriptions. Polybius wrote that Hannibal had crossed the highest of the Alpine passes: Col de la Traversette, between the upper Guil valley and the upper Po river is the highest pass. It is moreover the most southerly, as Varro in his De re rustica relates, agreeing that Hannibal's Pass was the highest in Western Alps and the most southerly. Mahaney et al. argue that factors used by De Beer to support Col de la Traversette including "gauging ancient place names against modern, close scrutiny of times of flood in major rivers and distant viewing of the Po plains" taken together with "massive radiocarbon and microbiological and parasitical evidence" from the alluvial sediments either side of the pass furnish "supporting evidence, proof if you will" that Hannibal's invasion went that way.
According to historian Theodore Ayrault Dodge, Hannibal marched in the direction of Mt. Du Chat towards the village of Aquste and from there to Chevelu, to the pass by Mt. Du Chat. There he found that the passes were fortified by the Allobroges. He sent out spies to ascertain if there was any weakness in their disposition. These spies found that the barbarians only maintained their position at the camp during the day, and left their fortified position at night. In order to make the Allobroges believe that he did not deem a night assault prudent, he ordered that as many camp-fires be lit as possible, in order to induce them into believing that he was settling down before their encampment along the mountains. However, once they left their fortifications, he led his best troops up to their fortifications and seized control of the pass.
Hiding his men in the mountain brush on a cliff that arose immediately above and to the right off Hannibal's route of march, about 100 feet or so above the path, Hannibal stationed his slingers and archers there. This overhang was an excellent place from which to attack an enemy while it was marching in column through the pass. The descent from this pass was steep, and the Carthaginians were having a hard time marching down this side of the pass, especially the bagg
Hannibal's crossing of the Alps