In an attack each unit must have sufficient driving power in itself to carry it through to its objective and enable it to hold its ground when it gets there. When a number of trenches have to be carried, considerable depth will be required, and the frontage must be reduced. A brigade usually has a front in attack of 250 to 350 yards, but this may be increased to 1,000 or 1,200 yards. A battalion should have a front of 250 to 350 yards. The battalion must be organized in depth in a series of waves. Two companies are usually put abreast in the first line and the others in the second line. Each company in both lines attacks in column of platoons at about 50 yards' distance, with intervals of three to five paces between men, so there would be eight lines of waves, of two platoons each. The 8th and 16th platoons, the two in rear forming the eighth wave, are usually not employed in the attack, but are left behind as a nucleus to form on in case of heavy casualties. The front line must not be less than 200 yards from the enemy's front line. The leading two or three waves are likely to meet machine gun fire, and generally move in extended order. Not more than two waves can be accommodated in one trench. Subsequent waves will move in line or in line of section columns in single file. Russian saps must be run out as far as possible across "No Man's Land" to be opened up immediately after the assault, as approach trenches. Ladders or steps are necessary to assist the leading waves in leaving the trenches, as they must move in lines. Provision must be made for bridges over the first line trenches for the rear waves. In the original assault line will be more suitable for both leading and rear waves. In later stages it is better for the rear waves to move in small and handy columns. In the original assault the distance between waves may be 75 to 100 yards; in later stages they may follow each other at 50 yards. In the original assault, zero, or the time for the assault to begin, may be fixed for the moment at which our barrage lifts from the enemy front trench, the infantry timing their advance so as to be close under our barrage before it lifts. In the later stages zero must be the moment at which our barrage commences, and this commencement will be the signal for the infantry to leave their trenches. Each wave is assigned its own objective. All watches must be synchronized in order that all units may start off at the appointed time.