A notable change to divisional structures during the war was completion of the shift from square divisions (composed of two brigades each with two regiments) to triangular divisions (composed of three regiments with no brigade level) that many European armies had started using in World War I. This was done to increase flexibility and to pare down chain-of-command overhead. The triangular division structure allowed the tactic of "two forward, one back", where two of the division's regiments could engage the enemy with one regiment in reserve.