=665.= To create a correct appreciation of the requirements of fire discipline, men are taught that the rate of fire, having constantly in view the available ammunition supply, should be as rapid as is consistent with accurate aiming; that the rate will depend upon the visibility, proximity, and size of the target; and that the proper rate will ordinarily suggest itself to each trained man usually rendering cautions or commands unnecessary. =666.= In attack, ammunition must be used with extreme caution in order that the highest rate of fire may be employed at the halt preceding the assault and in pursuing fire. =667.= In defense, when the target disappears behind cover, platoon leaders suspend fire, prepare their platoons to fire upon the point where it is expected to reappear, and greet its reappearance instantly with a vigorous burst of fire. In defense the available ammunition supply is not ordinarily so limited as in the attack. =668.= For communication between the firing line and the reserve or commander in rear certain signals are prescribed (par. 997). In transmission their concealment from the enemy's view should be insured. In the absence of signal flags the headdress or other substitute may be used. RANGES. =669.= For convenience of reference, ranges are classified as follows: 0 to 600 yards, close range. 600 to 1,200 yards, effective range. 1,200 to 2,000 yards, long range. Over 2,000 yards, distant range. The distance to the target must be determined as accurately as possible and the sights set accordingly. Aside from training and morale, this is the most important single factor in securing effective fire at the longer ranges. Except in a deliberately prepared defensive position, the most accurate and only practicable method of determining the range, in absence of a suitable mechanical range finder, will generally be to take the mean of several estimates made independently. _Estimation of ranges._--Five or six officers and men, selected from the most accurate estimators in the troop and designated as _range estimators_, should be specially trained in estimating distances. Whenever necessary and practicable, the captain assembles the range estimators, points out the target to them, and adopts the mean of their estimates. The range estimators then take their customary posts. When a range is announced, the men at once set their sights to correspond, and whenever practicable an examination of the pieces is made in order to verify the sight setting. (_C. C. D. R., No. 1, Apr. 26, 1917._)