Two connected accounts of the crossing survive. Polybius wrote within about seventy years of it. He says he questioned men who had been present and had gone over the Alps himself to see the ground (3.48.12), and he took the army's numbers from the bronze inscription Hannibal set up at Cape Lacinium (3.33.17-18, 3.56.4). Livy wrote two centuries after the event. His Alpine chapters follow Polybius closely in their sequence of incidents and are generally held to draw on the same Greek tradition, through the Roman annalist Coelius Antipater, whose own source for the march was Silenus, a Greek who travelled with Hannibal. Everything else, from Strabo's list of passes to Ammianus, is a summary of these two or a one-line aside. So the two accounts are one tradition and do not count as independent witnesses to the route. Where Livy has a name that Polybius lacks, the name may come from Coelius, from Livy's own geography, or from a mistake.
The march to the foot of the Alps
Polybius gives the distances twice. In the geographical summary of the march he counts 1,600 stades from Emporion to the Rhône crossing, then:
ἀπὸ δὲ τῆς διαβάσεως τοῦ Ῥοδανοῦ πορευομένοις παρ᾽ αὐτὸν τὸν ποταμὸν ὡς ἐπὶ τὰς πηγὰς ἕως πρὸς τὴν ἀναβολὴν τῶν Ἄλπεων τὴν εἰς Ἰταλίαν χίλιοι τετρακόσιοι. λοιπαὶ δ᾽ αἱ τῶν Ἄλπεων ὑπερβολαί, περὶ χιλίους διακοσίους.From the crossing of the Rhône, for those going along the river itself towards its sources, as far as the ascent of the Alps towards Italy, 1,400 stades. There remain the passes of the Alps, about 1,200.Polybius 3.39.9-10 (Büttner-Wobst). The preceding clause, which says the road to the Rhône had "now" been measured and marked every eight stades by the Romans, refers to the milestones of the Via Domitia (after 118 BC) and shows this passage was written or revised late in Polybius's life.
The narrative then supplies the pieces. After the crossing Hannibal marched "along the river, away from the sea, as if towards the east, as if making for the interior of Europe" (3.47.1). Four days from the crossing he reached the Island:
Ἀννίβας δὲ ποιησάμενος ἑξῆς ἐπὶ τέτταρας ἡμέρας τὴν πορείαν ἀπὸ τῆς διαβάσεως ἧκε πρὸς τὴν καλουμένην Νῆσον, χώραν πολύοχλον καὶ σιτοφόρον ... ᾗ μὲν γὰρ ὁ Ῥοδανός, ᾗ δ᾽ Ἰσάρας προσαγορευόμενος, ῥέοντες παρ᾽ ἑκατέραν τὴν πλευράν, ἀποκορυφοῦσιν αὐτῆς τὸ σχῆμα κατὰ τὴν πρὸς ἀλλήλους σύμπτωσιν. ἔστι δὲ παραπλησία τῷ μεγέθει καὶ τῷ σχήματι τῷ κατ᾽ Αἴγυπτον καλουμένῳ Δέλτα ...Hannibal, marching for four days in succession from the crossing, came to the place called the Island, a populous and corn-growing district ... for the Rhône on one side and the river called the Isère on the other, flowing along each flank, bring its shape to a point where they meet. In size and shape it resembles the Egyptian Delta ...Polybius 3.49.5-7. "Isère" (Ἰσάρας) stands in no manuscript. Most manuscripts read Σκάρας and the Munich manuscript Σκώρας (Schweighäuser 1789, vol. V, pp. 594-595); Casaubon printed Ἄραρος from Livy's vulgate; Ἰσάρας is Cluverius's conjecture of 1624 (Italia Antiqua I.33), explained by Holstenius as a copyist's misreading of ΟΙΣΑΡΑΣ, and every edition since Schweighäuser prints it without an apparatus note. Walters and Conway, editing Livy, cite the Polybian reading and propose the Sorgue instead, following Spenser Wilkinson (1911), who put the Island at L'Isle-sur-la-Sorgue.
The Island's elder prince, whom Hannibal had restored to power, re-equipped the army with weapons, clothing and boots "for the crossing of the mountains". And, "most important of all", he escorted it with his own force until it neared the ascent of the Alps, because the Carthaginians were uneasy about "the march through the Gauls called Allobroges" (3.49.11-13). Then:
Ἀννίβας δ᾽ ἐν ἡμέραις δέκα πορευθεὶς παρὰ τὸν ποταμὸν εἰς ὀκτακοσίους σταδίους ἤρξατο τῆς πρὸς τὰς Ἄλπεις ἀναβολῆς ... ἕως μὲν γὰρ ἐν τοῖς ἐπιπέδοις ἦσαν, ἀπείχοντο πάντες αὐτῶν οἱ κατὰ μέρος ἡγεμόνες τῶν Ἀλλοβρίγων ...Hannibal, having marched in ten days along the river for 800 stades, began the ascent towards the Alps ... For as long as they were in the flat country, the several chieftains of the Allobroges kept away from them ...Polybius 3.50.1-2. The Greek says "the river" and does not say which one; no manuscript varies. Paton's Loeb prints "along the bank of the Isère" and Shuckburgh "along the river bank"; the name is Paton's addition, and a reader who relies on his translation is given the Isère route with it. Schweighäuser's argument for the Isère was arithmetic: 1,400 stades to the ascent less 800 leaves 600 for the four days to the Island, about 28 km a day, which fits a crossing near Roquemaure and an Island at Valence, and does not fit any confluence nearer the sea.
Livy's version of the same stretch is the one passage in either author that names peoples between the Rhône and the Alps:
Quartis castris ad Insulam pervenit. Ibi Isara Rhodanusque amnes diversis ex Alpibus decurrentes agri aliquantum amplexi confluunt in unum; mediis campis Insulae nomen inditum. Incolunt prope Allobroges ... Sedatis Hannibal certaminibus Allobrogum cum iam Alpes peteret, non recta regione iter instituit sed ad laevam in Tricastinos flexit; inde per extremam oram Vocontiorum agri tendit in Tricorios, haud usquam impedita via priusquam ad Druentiam flumen pervenit.At the fourth camp he reached the Island. There the rivers Isère and Rhône, running down from different parts of the Alps and enclosing a fair extent of land, join into one; the plain between them is called the Island. The Allobroges live near by ... When the quarrels of the Allobroges had been settled and Hannibal was now making for the Alps, he did not go straight on but turned left into the Tricastini; from there he held along the outer edge of the Vocontii's land into the Tricorii, the road nowhere obstructed until he reached the river Druentia.Livy 21.31.4-9 (Foster's Loeb text as printed on la.wikisource). The Puteanus manuscript is lost for this stretch. The other manuscripts read sarar (M), bisarar (D) and arar (C, A, N): the Arar is the Saône, which is impossible here, and Silius Italicus 3.452 already read it. Isara is again Cluverius's conjecture, printed by Weissenborn and Müller, Riemann and Benoist, and Foster; Walters and Conway obelise †Sarar† in the Oxford text, remark that "the reckoning of days excludes these rivers", and prefer Conway's Sorgas. The manuscripts also give the singular amnis; the Oxford text prints Trigorios where later editors print Tricorios from Ammianus. The Druentia is the Durance. The Tricastini lived around Saint-Paul-Trois-Châteaux, south of the Isère; the Vocontii held the Drôme and the Baronnies; the Tricorii are placed in the upper Drac or the Trièves. A march from an Island at the Isère that goes "left" into the Tricastini goes back downstream.
Livy then has Hannibal cross the Durance "in flood" and reach the Alps from the Durance "by a mostly level route, with the good will of the Gauls who lived there" (21.32.6: ab Druentia campestri maxime itinere ad Alpes cum bona pace incolentium ea loca Gallorum pervenit). That sentence is the Livian counterpart of Polybius's ten days in flat country, and it sits oddly with the Durance, whose valley above Sisteron is not level.
The ascent
The first fight is with the Allobroges, at a defile where the tribesmen hold the heights by day and go home at night to a town close by. Hannibal seizes the heights after dark, the column is mauled in the pass the next day, and he takes the town, which feeds the army for two or three days (Polybius 3.50.3-3.51.13; Livy 21.32.8-33.11 calls the town a castellum quod caput eius regionis erat, "the fort that was the chief place of that district"). He rests a day and marches on. On the fourth day "those living around the pass" meet him with branches and wreaths. Guided by them for two days, he is attacked in "a difficult and precipitous gorge" where rocks are rolled down from above, and spends a night with half the army "at a certain strong white rock" (περί τι λευκόπετρον ὀχυρόν, 3.53.5; Livy 21.34.9 has the night without cavalry and baggage but no rock). Next day the enemy withdraw and he "advanced towards the highest passes of the Alps" (3.53.6). Wherever the elephants are in the column, the tribesmen keep off (3.53.8; Livy 21.35.3).
ἐναταῖος δὲ διανύσας εἰς τὰς ὑπερβολὰς αὐτοῦ κατεστρατοπέδευσε καὶ δύ᾽ ἡμέρας προσέμεινε ... τῆς δὲ χιόνος ἤδη περὶ τοὺς ἄκρους ἁθροιζομένης διὰ τὸ συνάπτειν τὴν τῆς Πλειάδος δύσιν ...On the ninth day he reached the summit of the pass, camped there and stayed two days ... The snow was already gathering on the heights, because the setting of the Pleiades was near ...Polybius 3.53.9-3.54.1. Livy 21.35.4-6: nono die in iugum Alpium perventum est per invia pleraque et errores ... biduum in iugo stativa habita ... nivis etiam casus occidente iam sidere Vergiliarum: "on the ninth day they reached the ridge of the Alps, mostly through trackless ground and by wanderings" caused by treacherous or guessing guides; two days' halt on the ridge; a fall of snow "with the constellation of the Pleiades now setting".
The view from the top
ἐπειρᾶτο συναθροίσας παρακαλεῖν, μίαν ἔχων ἀφορμὴν εἰς τοῦτο τὴν τῆς Ἰταλίας ἐνάργειαν· οὕτως γὰρ ὑποπεπτώκει τοῖς προειρημένοις ὄρεσιν ὥστε συνθεωρουμένων ἀμφοῖν ἀκροπόλεως φαίνεσθαι διάθεσιν ἔχειν τὰς Ἄλπεις τῆς ὅλης Ἰταλίας. διόπερ ἐνδεικνύμενος αὐτοῖς τὰ περὶ τὸν Πάδον πεδία ... ἅμα δὲ καὶ τὸν τῆς Ῥώμης αὐτῆς τόπον ὑποδεικνύων ...He gathered them and tried to encourage them, having one resource for it: the visible presence of Italy. For it lies so close under these mountains that when both are seen together the Alps appear to stand to the whole of Italy as a citadel to a city. So, pointing out to them the plains of the Po ... and at the same time indicating the direction of Rome itself ...Polybius 3.54.2-3. The Teubner of 1882 printed ἐνέργειαν ("the reality of Italy") and that of 1905 returned to ἐνάργειαν ("the clear sight of Italy"); the next clause, "pointing out to them the plains of the Po", settles the sense either way. Livy 21.35.8 moves the scene a day later and off the col: praegressus signa Hannibal in promunturio quodam, unde longe ac late prospectus erat, consistere iussis militibus Italiam ostentat subiectosque Alpinis montibus circumpadanos campos, "Hannibal, going ahead of the standards to a certain promontory from which there was a far and wide view, halted the soldiers and showed them Italy and the plains around the Po lying beneath the Alps."
The descent
οὔσης γὰρ στενῆς καὶ κατωφεροῦς τῆς καταβάσεως ... ἅμα δὲ τῷ παραγενέσθαι πρὸς τοιοῦτον τόπον, ὃν οὔτε τοῖς θηρίοις οὔτε τοῖς ὑποζυγίοις δυνατὸν ἦν παρελθεῖν διὰ τὴν στενότητα, σχεδὸν ἐπὶ τρί᾽ ἡμιστάδια τῆς ἀπορρῶγος καὶ πρὸ τοῦ μὲν οὔσης, τότε δὲ καὶ μᾶλλον ἔτι προσφάτως ἀπερρωγυίας ...The descent being narrow and steep ... when they came to a place that neither the elephants nor the pack animals could pass because of its narrowness, the cliff-path having broken away for about three half-stades, before this already and now recently still more ...Polybius 3.54.5-7. Three half-stades is about 270-280 m. Livy 21.36.2 gives a figure as a height: natura locus iam ante praeceps recenti lapsu terrae in pedum mille admodum altitudinem abruptus erat, "the place, already steep by nature, had been broken away by a recent landslip to a depth of fully a thousand feet." The words in pedum mille are a Renaissance restoration by Valla and a later hand in one manuscript of the corrupt reading impeditus dum ille; they are accepted by the Oxford editors but are not a manuscript datum. The manuscript of Polybius reads τῆς γῆς ἀπερρωγυίας, "of the broken-away ground", where the Teubner prints τῆς ἀπορρῶγος; the "three half-stades" are secure.
ἐπὶ γὰρ τὴν προϋπάρχουσαν χιόνα καὶ διαμεμενηκυῖαν ἐκ τοῦ πρότερον χειμῶνος ἄρτι τῆς ἐπ᾽ ἔτους πεπτωκυίας ...For on top of the old snow that had remained from the previous winter the snow of this year had just fallen ...Polybius 3.55.1; Livy 21.36.5 super veterem nivem intactam nova modicae altitudinis. The old snow is met on the descent, below the col, where the broken path was.
Hannibal camped "on the ridge" (περὶ τὴν ῥάχιν, 3.55.6) after clearing the snow, and set the men to build up the cliff-path. One day's work let the horses and mules through to snow-free pasture; three more days, with the Numidians working in relays, brought the elephants over, "in a wretched state from hunger" (3.55.7-8). Livy adds the story of the rock split with fire and vinegar (21.37.2-3), which Polybius does not have. Then "on the third day from the cliffs" the whole army reached the flat country (3.56.1; Livy 21.37.6 triduo inde ad planum descensum). The crossing of the Alps took fifteen days and the march from New Carthage five months (3.56.3; Livy 21.38.1).
Where he came down
κατῆρε τολμηρῶς εἰς τὰ περὶ τὸν Πάδον πεδία καὶ τὸ τῶν Ἰνσόμβρων ἔθνος ... [3.60.8] τῶν Ταυρίνων, οἳ τυγχάνουσι πρὸς τῇ παρωρείᾳ κατοικοῦντες, στασιαζόντων μὲν πρὸς τοὺς Ἴνσομβρας ...He came down boldly into the plains of the Po and the nation of the Insubres ... [3.60.8] the Taurini, who live at the foot of the mountains, being at feud with the Insubres ...Polybius 3.56.3 and 3.60.8-9. The first army action in Italy is the three-day siege of the Taurini's chief town (Turin). Livy 21.38.5: Taurini Galli proxima gens erat in Italiam degresso, "the Taurini were the nearest people to him when he came down into Italy."
Livy then gives the only ancient discussion of the pass itself:
Id cum inter omnes constet, eo magis miror ambigi, quanam Alpes transierit, et volgo credere Poenino — atque inde nomen ei iugo Alpium inditum — transgressum, Coelium per Cremonis iugum dicere transisse; qui ambo saltus eum non in Taurinos sed per Salassos Montanos ad Libuos Gallos deduxissent. Nec veri simile est ea tum ad Galliam patuisse itinera; utique quae ad Poeninum ferunt obsaepta gentibus Semigermanis fuissent.Since everyone agrees on that, I wonder the more that there is doubt about where he crossed the Alps, and that the common belief is that he crossed by the Poeninus, from which that ridge of the Alps got its name, while Coelius says he crossed by the Cremonis iugum; both those passes would have brought him not to the Taurini but through the Salassi Montani to the Libui Galli. Nor is it likely that those routes were open towards Gaul at that time; those leading to the Poeninus at least would have been blocked by half-German tribes.Livy 21.38.6-8. The Poeninus is the Grand St Bernard, whose name Livy goes on to derive from the god worshipped on its summit. Coelius's Cremonis iugum is usually taken as the Petit St Bernard, from the name of Mont Cramont above Courmayeur; the identification is old and unproved. Livy's objection stands on its own: any pass into the Aosta valley lands the army among the Salassi, and the sources agree it landed among the Taurini.