(iv) =Oblique Winds.=--Oblique winds, or winds blowing from any intermediate direction between a right angle and a front or rear wind, have the same effect in varying degree as side winds. Oblique winds, in addition, affect the bullet to some extent in the same way as head and rear winds. =4. Allowance for Head and Rear Winds.=--No fixed rules can be laid down regarding the degree to which elevation should be increased or decreased at different ranges for head and rear winds. For practical purposes, the effect of these winds may be disregarded at ranges under 1,000 yards. At longer ranges, fire-unit commanders will use their judgment in directing fire, whether they will allow for strong head and rear winds by increasing or decreasing elevation, and to what extent. =5. Allowance for Side and Oblique Winds= (see also Sec. 20, _Aiming-Off_).--(i) No fixed rules can be laid down as to the degree of allowance to be made by aiming-off for side and oblique winds of varying direction and velocity. Owing to the increased time during which the bullet is exposed to the effect of wind, and owing to the height attained in its flight, the allowance for wind at long ranges must be out of all proportion greater to that necessary at close range. (ii) At close range, whether fire is distributed along the dense line of an infantry attack or concentrated on narrow-fronted attacking columns, the effect of side wind will cause little, if any, loss of fire effect. Individual soldiers, however, in taking the deliberate aim necessary for fire effect, should aim off for side winds of different velocity (see Sec. 20, para. 3). (iii) In directing fire beyond close range, fire-unit commanders must use their judgment in allowing for deflection due to side and oblique winds by including directions for aiming-off in fire orders. The extent of the allowance will in every case depend upon a variety of factors, including the direction and velocity of the wind and the distance of the target. Neglect to make due allowance for strong winds at longer ranges may lead to loss of fire effect, more particularly in the case of concentrated fire aimed at narrow-fronted targets, such as a machine-gun. =6. Effect of Light.=--In bad light, the foresight is less distinctly seen than in good light, and more of it is unconsciously taken into the line of sight. For practical purposes, the effect of light may be disregarded in firing at all ranges. Section =11=.--Need for Collective Fire. =1.= (i) Only exceptional targets and very favourable atmospheric conditions will justify soldiers in opening individual fire at distances beyond about 600 yards. Collective fire is necessary to give reasonable assurance of fire effect beyond about 600 yards up to about 1,400 yards, which is usually the limit of effective rifle fire. _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._