Battle of Alesia
Caesar engaged in the Gallic Wars (58–50 BC), which led to his conquest of Gaul beyond Gallia Narbonensis. When the Helvetii, a federation of tribes from what is now Switzerland, planned a migration to the Atlantic coast through Gaul, Caesar went to Geneva and forbade the Helvetii to move into Gaul. While he went to Gallia Cisalpina to collect three other legions, the Helvetii attacked the territories of the Aedui, Ambarri, and Allobroges, three Gallic tribes, which called for Caesar’s help. Caesar and his Gallic allies defeated the Helvetii. The Gallic tribes then asked for Caesar to intervene against an invasion by the Suebi, a Germanic tribe. Caesar defeated the Suebi. In 57 BC he intervened in intra-Gallic conflicts and marched on the Belgae of northern Gaul. From then on he conquered the Gallic peoples one by one. His successes in Gaul brought Caesar political prestige in Rome and great wealth through the spoils of wars and the sale of war captives as slaves.
Great St Bernard Pass
The pass had entered history with the Gallic invasion of 390 BC. The last Gallic invasion over it occurred in May, 1800, under the direction of the 30-year-old First Consul of the French Republic, Napoleon Bonaparte. An Austrian army of 140,000 men had laid siege to French-occupied Genoa on the west coast of northern Italy. Napoleon traversed the pass with 40,000 men and ⅓ of their heavy artillery sending another 20,000 over three other passes as a diversion, intending to strike the Austrian rear. The panicked Austrians were unable to assemble fast enough to meet the French en masse but rather in a piecemeal way in June 1800, and so were defeated first at the Battle of Montebello and then at the Battle of Marengo.