Codenamed Operation Izard, the attack on the Mont Cenis pass began on the 5 April. It was carried out by the 3,000 men of the 7th Half-brigade of Chasseurs Alpins belonging to the 27th Alpine Division, led by Colonel Alain Le Ray, reinforced by two batteries of heavy artillery from the 1st Free French Division. The position was defended by a battalion of the 5th Gebirgsjäger Division and another battalion from the Paratroop Regiment Folgore supported by German artillery, in all some 1,500 men.