Charmaix Valley communicated with Italy via the Fréjus, Roue and Vallée-Etroite passes; each pass was defended by an infantry outpost and field positions.
In the rear, two imposing artillery works, Lavoir and Pas-du-Roc, blocked the strategic passages and could support the outposts with their guns and mortars.
Sapey artillery work provided general support for the sector.
Major Simian was responsible for the defense of the valley, with 1,300 men from 81 Fortress Alpine Battalion (BAF), 1st Company, 71BAF, scout-skiersplatoon, 28Alpine Infantry Battalion (BCA), one company of 281Infantry Regiment (RI), two companies of 343Infantry Regiment and three batteries of 164Position Artillery Regiment.
Modane was the main objective of the Italians of the Superga division and the Alpini Val Dora battalion, that is to say 4000 men. They were supported by a large artillery force positioned around Bardonecchia.
On 21 June, supported by artillery, the Italian infantry launched an attack. French artillery pinned down the attackers. The outposts resisted all attacks.
On 22, 23 and 24 June, all Italian attempts failed in the face of the deluge of French fire.
The French artillery fired 19,000 shells in four days.
French losses were one killed and a few slightly wounded. The Italians lost 33 killed, 121 wounded and 430 frostbitten.