The line formation provided the best front for volley fire. However the line could not change direction easily and was open to attack by cavalry. Frederick the Great used the line formation, or “march by lines” as a part of his oblique order to fix this problem. The other part of the oblique order was the “attack in echelon” (change to column formation and angle slightly towards the enemy). This way his line of soldiers, usually two ranks deep, could easily change the direction they faced.