Andrew Roberts summarizes (in Napoleon: A Life), Napoleon’s first few months in power:
In less than fifteen weeks Napoleon had effectively ended the French Revolution, seen off the Abbé Sieyès, given France a new constitution, established her finances on a sound footing, muzzled the opposition press, started to end both rural brigandage and the long-running war in the Vendée, set up a Senate, Tribunate, Legislative Body and Conseil d’État, appointed a talented government regardless of past political affiliations, rebuffed the Bourbons, made spurned peace offers to Britain and Austria, won a plebiscite by a landslide (even accounting for the fraud), reorganized French local government and inaugurated the Banque de France.
‘Today I’m a sort of mannequin figure that’s lost its liberty and happiness,’ Napoleon wrote to Moreau, the commander-in-chief of the Army of the Rhine, on March 16 as France prepared to re-engage Austrian forces. ‘Grandeur is all very well, but only in retrospect and in the imagination. I envy your happy lot; you are going to accomplish grand things with your gallant men. I would willingly exchange my consular purple for the epaulette of a brigadier under your orders… I strongly hope that the circumstances may allow me to come and give you a helping hand.’ Three weeks later circumstances would allow just that, when the Austrian General Michael von Melas defeated General Nicolas Soult at the battle of Cadibona, pushing him back towards Savona and forcing Masséna into Genoa, which was subsequently besieged. It was time to return to the battlefield.
He had ordered the covert formation of a 30,000-strong Army of the Reserve based at Dijon on January 7, 1800:
He was counting on an element of surprise: no one had taken an army over the Alps since Charlemagne, and before him Hannibal. Although Napoleon wouldn’t be travelling with elephants, he did have Gribeauval 8-pounder and 4-pounder cannon, whose barrels weighed over a quarter of a ton, to heave over the mountain range. Snow was still thick on the ground in early May, when the advance began, so Marmont devised sledges for the barrels made out of hollowed-out tree-trunks, which one hundred men at a time hauled up the Alps and then down again, to drumbeats. (Since the Italian side is much steeper than the French, they found it harder going down than up.)
Money and supplies were sent ahead to the monasteries and hostelries along the route, and local guides were hired and sworn to secrecy.
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‘An army can pass always, and at all seasons,’ Napoleon told a sceptical General Dumas, ‘wherever two men can set their feet’.
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In the strategy meeting he allegedly asked Bourrienne where he thought the decisive battle would be fought. ‘How the devil should I know?’ answered his Brienne-educated private secretary. ‘Why, look here, you fool,’ said Napoleon, pointing to the plains of the River Scrivia at San Giuliano Vecchio, explaining how he thought Melas would manoeuvre once the French had crossed the Alps. It was precisely there that the battle of Marengo was fought three months later.
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In all 51,400 men crossed the Alps, with 10,000 horses and 750 mules. They went by single file in some places, and had to start at dawn every day to reduce the risk of avalanches once the sun had risen.
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Napoleon rode a horse for almost the whole journey over the Alps, and a mule (as it was more sure of foot) for the iciest stretch around Saint-Pierre.
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It was at this stage of the campaign that the sheer ruthlessness that helped make Napoleon so formidable a commander revealed itself once again. Instead of marching south to relieve starving Genoa, as his troops and even his senior commanders assumed he would do, he wheeled eastwards towards Milan to seize the huge supply depot there and cut off Melas’s line of retreat towards the Mincio river and Mantua. Ordering Masséna to hold out for as long as possible so that he would tie down Ott’s besieging force, Napoleon outfoxed Melas, who had taken it for granted that Napoleon would try to save Genoa. He had therefore left Nice and marched back from Turin to Alessandria to try to head Napoleon off.
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At 6.30 p.m. that same day Napoleon entered Milan by the Verceil Gate in the pouring rain and installed himself at the archducal palace, staying up until 2 a.m. dictating letters, receiving Francesco Melzi d’Eril, who had run the Cisalpine Republic, setting up a new city government and releasing political prisoners interned by the Austrians, who had used Milan as their regional headquarters. He also read Melas’s captured despatches from Vienna, which told him the enemy’s strengths, dispositions and state of morale.
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Genoa surrendered on June 4, by which time around 30,000 of its 160,000 inhabitants had died of starvation and of diseases associated with malnutrition, as had 4,000 French soldiers. Another 4,000 soldiers who were fit enough to march out were allowed to return to France with the honours of war, and a further 4,000 sick and wounded were transported to France in Royal Navy ships under Admiral Lord Keith, who had blockaded the port but saw the advantage of evacuating so many French away from the theatre of war.
Masséna’s health was broken, not least because he had insisted on only eating what his troops did. He never wholly forgave Napoleon for not rescuing him. Equally, Napoleon – who was never besieged in the whole of his career – criticized Masséna for not having held out for ten days longer, recalling when in exile on St Helena, ‘A few old men and some women might have died of hunger, but then he would not have surrendered Genoa. If one thinks always of humanity – only of humanity – one should give up going to war. I don’t know how war is to be conducted on the rosewater plan.’
The idea that only Hannibal and Charlemagne had crossed the Alps with armies before is ludicrous. Multiple French armies crossed the Alps into Italy on their way to be trounced by the Spaniards in the 16th century. Before Charlemagne, a ton of Frankish warlords did the crossing to fight the Lombards and/or the Byzantines. Under the Roman Empire, crossing the Alps on the way to fight a civil war was routine.
The eras of the Roman expansion and the High Middle Ages were relatively warm, and many of the passes through the Alps were ice-free. Napoleon, however, fought his wars during the Little Ice Age, and many Alpine passes might have had substantial ice barriers.