Complex sentence: The Arditi approached enemy trenches while these were being shelled by Italian artillery, and just as the barrage was lifted they jumped inside the trench while the enemy was huddling down and used their dagger in close quarter to suppress enemy resistance.
Split into simpler sentences: The Arditi approached enemy trenches while they were being shelled by Italian artillery. Just as the barrage was lifted they would jump inside the trench while the enemy was huddling down, and use their daggers at close quarters to suppress enemy resistance.