=9. Duties of Observers.=--Men trained as observers will be employed, as necessary, to assist fire-unit commanders in observation of fire, in watching the enemy and neighbouring troops, and in keeping up communication between platoons. Observers will also be trained in the duties of ranging and control of fire, so that they can carry them out if fire-unit commanders are incapacitated. Section =43=.--Effect of Fire at Different Ranges on Various Formations and Objectives. =1. Effect of Fire at Various Ranges=--(i) =Close Range=.[21]--Owing to the flatness of the trajectory, it should be possible to obtain the maximum effect from rifle fire at targets within close range--given a good field of fire and the absence of dead ground and other conditions unfavourable to fire effect at all ranges--_provided that fire discipline is good and that individual soldiers select their targets and fire carefully, making due allowance for elevation by aiming down when necessary_. (ii) =Effective Ranges.=--Between 600 and 1,400 yards, carefully controlled collective fire produces better results than the uncontrolled fire of individual men, which ceases to be sufficiently effective beyond ranges of about 600 yards to counterbalance the expenditure of ammunition involved. At effective ranges troops advancing steadily and rapidly suffer less than when they remain lying down, even under moderately good cover. This is due to the moral effect on the enemy and to the constant alteration of the range. (iii) =Long and Distant Ranges.=--Beyond 1,400 yards the fire of even large and well-controlled units of infantry has seldom much effect upon the decision of the struggle for superiority of fire. Exceptional circumstances, such as the appearance of considerable bodies of the enemy in vulnerable formations, may, however, justify the use of long-range fire, especially in the defence. =2. Effect of Rifle Fire on Various Formations and Objectives=--(i) =Infantry.=--On open ground swept by effective rifle fire an extended line is the least vulnerable formation for infantry, and on such ground it will usually be advisable to extend before it becomes necessary for the advancing troops to open fire. The greater the extension of a line, the fewer will be the casualties, but the less will be its fire effect [see Preface, para. 8 (i)].