The French troops were divided into three attacking columns and their movements began at about 16:30 pm.

The forces involved amounted to 32 French battalions against 13 allied. So, the decision was taken to attack immediately. French intelligence discovered that the allied forces were fortifying the pass, while the main Austrian army had left the siege of Genoa to reach the Alps. Having predicted that the French would move through it, the King Charles Emmanuel III of Savoy had fortified the area with an entrenched camp garrisoned with 7,000 men of 13 infantry battalions: 9 Sardinian, and 4 Austrian. An army of about 20,000 soldiers under the command of Louis Charles Armand Fouquet de Belle-Isle (called the Chevalier de Belle-Isle, the younger brother of the Marshal de Belle-Isle) was divided into two corps: one went down the Moncenisio towards Exilles, while the other advanced towards the Chisone Valley, in order to reach the Assietta ridge from the south side. The strategic goal of the French offensive was the siege and the capture of the Fort of Exilles, a fortress in the Susa Valley on the road from Briançon to Turin. The battle occurred 19 June 1747, and was the bloodiest single day battle not only of the War of Austrian Succession (1740-1748) in Italy, but also of the whole military history of the Alps, and of mountain warfare in general. 'You have to die in Piedmont!' An old folk song, still played in the western Alps, speaks about the French regiments that were incoming from the Mongeneve Pass in order to attack a combined Austro-Sardinian force entrenched on the Assietta Plateau at 2,500 meters (about 8,200 ft) of elevation in the Cottian Alps, which controls two main roads from France to the Kingdom of Sardinia's capital, Turin.

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