At 06:41, 2,200 guns opened fire, many targeting the valley road along which reserves were advancing to plug the gap. At 08:00 two large mines were detonated under strong points on the heights bordering the valley and the infantry attacked. Soon they penetrated the almost undefended Italian fortifications in the valley, breaching the defensive line of the Italian Second Army between the IV and XXVII Corps. To protect the attackers' flanks, Alpine Troops infiltrated the strong points and batteries along the crests of the adjoining ridges, Matajur and Kolovrat, laying out their telephone lines as they advanced to maintain contact with their artillery. Specially-trained and equipped stormtrooper units led attacks, making good use of the new German model 08/15 Maxim light machine gun, light trench mortars, mountain guns, flamethrowers and hand grenades.