Superiority of fire can only be gained by the close { 39} co-operation of the artillery and infantry at every stage of the battle, and unless infantry co-operate, the artillery is not likely to produce any decisive effect. Long-range machine-gun fire is an important auxiliary to the artillery in covering and supporting the advance of attacking infantry. Enfilade fire, the most telling of all, is more easily brought to bear than of old owing to the increase in the effective range and in the rate of fire. Supports and local reserves will usually co-operate most effectively with forward troops by bringing fire to bear upon the flank of such bodies of the enemy as are holding up a movement by frontal fire. During the counter-attack for the recapture of _The Bluff_, in the Ypres Salient (March 2, 1916) by troops of the 3rd and 17th Divisions, the right and centre gained their objectives. The left attacking party, at the first attempt, failed to reach the German trenches, but those who had penetrated to the German line on the right realised the situation and brought a Lewis gun to bear on the enemy's line of resistance, completely enfilading his trenches, and thus enabling the left company to reach its goal.
MOVEMENT.--The influence of movement is inseparable from that of fire, as it enables fire to be opened and is a means of escaping the full effects of fire; while it is often possible to move one unit only in conjunction with the fire of another. It can also be used to relieve one unit from the effects of fire concentrated upon it by moving another unit against the enemy. A steady and rapid advance of troops has the twofold effect of closing to a range from which an ascendency in the fire-fight can be secured, and also of reducing the losses of the advancing force, for if the troops remained stationary in the open under heavy fire, at a known range, the losses would clearly be greater than if they advanced, and would be suffered without gaining ground towards the objective, while the closer the { 40} assaulting line gets to the objective, and the steadier its advance, the less confidence will the enemy have in their power to stem the advance, and the fewer casualties will be suffered in consequence. No "sealed pattern" is laid down as to the movement and formation of infantry under fire, but certain definite principles are put forward in the text-books. Where security is the first need, as in the case of protecting forces (advanced, flank, or rear guards), movement should be effected by bounds from one tactical position to another under covering fire from supporting troops; where the objective is the primary consideration, security must be subordinated to the need of reaching the objective. Against artillery fire, or long-range infantry fire, the formation recommended by the text-books is small shallow columns, each on a narrow front, such as platoons in fours or sections in file, arranged on an irregular front, so that the range from the enemy's guns to each is different. Troops coming suddenly under such fire will avoid casualties more easily by moving forward and outwards in this way rather than by remaining under such cover as may be improvised in a position the exact range of which is obviously known to the enemy. Against effective machine-gun or rifle fire deployment into line, or into "arrowhead" formation with the flanks thrown well back, is preferable to a single line extended at so many paces interval, as it is scarcely more vulnerable and is infinitely easier to control.