(ii) Sweeping Fire ([Fig. 48]).—Fire distributed laterally is called sweeping fire. Such fire is to be preferred for neutralizing an enemy’s fire along any portion of his front.
(iii) Searching Fire[22] ([Fig. 7]).—Fire distributed in depth is called searching fire. Such fire gives greater assurance that some portion of the fire will be effective when the target has not been located definitely, or when serious errors in sighting are to be expected.
10. Oblique and Enfilade Fire ([Fig. 48]).—Both oblique and enfilade fire have greater moral and material effect than frontal fire, for they usually come from an unexpected direction, and the targets presented to them are generally more vulnerable than those presented to frontal fire. In defence, opportunities for the employment of enfilade fire may be created by careful pre-arrangement between the commanders of adjoining units.
11. Converging Fire ([Fig. 48]).—Converging fire is fire directed at a target from two or more different points simultaneously. The moral and material effect of converging fire may be very great, as it may combine the effects of frontal, oblique, and enfilade fire at one and the same time (Demonstration No. 3, p. 222).
12. Mutual Support ([Fig. 48]).—(i) The various portions of the firing-line will also on occasions be able to afford each other mutual support by fire, and all commanders must be on the alert to assist units on their flanks in this manner when the situation requires. Covering fire in mutual support should consist of heavy bursts of rapid fire, sustained during the forward movement, and directed at the enemy to the front of the advancing unit, as well as to the front of the unit firing (Practice No. 1, p. 226).
(ii) Mutual support in the firing-line will as a rule, however, be more automatic than deliberately arranged, and in no case must its employment be allowed to induce hesitation in the advance. The paramount duty of all leaders in the firing-line is to get their troops forward, and if every leader is imbued with a determination to close with the enemy, he will be unconsciously assisting his neighbour also, for as a rule the best method of supporting a neighbouring unit is to advance.
13. Covering Fire ([Fig. 48]).—(i) When the ground permits, it is generally necessary to detail special detachments of infantry to provide covering fire for the leading troops. These detachments will usually be detailed by battalion commanders from local reserves in the original distribution for the attack, but any commander, at any stage of the fight, may detail troops from those under his command to assist his advance. No fire-unit commander, however, is justified, on his own initiative, in withdrawing from the advance or ceasing to seek an opportunity to advance in order to constitute his command a detachment for providing covering fire (Demonstration No. 6, p. 223).
(ii) In undulating or mountainous country it may be possible for detachments employed to provide covering fire to cover the advance from positions in rear, but in flat country it may be dangerous or impossible for infantry or machine-guns to fire over the heads of their own troops, and opportunities for providing covering fire should be sought on the flanks.
(iii) Troops detailed to provide covering fire for the advance must take care to select as targets those bodies of the enemy whose fire is chiefly checking the advance. Great difficulty will often be experienced in discovering which these bodies are, and all ranks must be on the alert to notice any indication which may help to discover them.
(iv) As soon as their fire ceases to be effective in aiding the advance of the firing-line, it is the duty of troops detailed to provide covering fire at once to join in the advance, unless definite orders to the contrary have been received.