Instructions For the Rifleman in the Trenches
The following is taken from the Manuel du Chef de Section d'Infanterie ("The Manual of the Infantry Section Leader") dated January 1918.
General Rules and Limits:
Above all, fire discipline is stressed for the isolated soldier. In principle, the rifleman fires only in the following circumstances:
If a soldier has orders to fire on targets of opportunity when they should appear (especially when on sentry or look-out duty) -- which is generally the case in the trenches -- he must estimate the distance (for more info, see below). Moreover, the rifleman must be governed by the guideline of not firing when:
The point to aim at is the lower edge of the visible portion of the target. If the target is moving across the rifleman's field of vision, aim at the edge toward the direction which the target is moving. If there is a cross-wind, aim at the edge of the target toward the wind. The chances are very small of hitting an individual at more than 250 meters distant moving across the field of view or standing in a strong cross-wind. On account of the flatness of trajectory, there is as much a chance of success at hitting the target at short ranges with the battle sight as with a more exact setting. The following simple rule applies to firing:
The observance of fire discipline and of the limits of employment of individual fire must be particularly strict when the necessity of not revealing one's presence and of maintaing the element of surprise is paramount. If the isolated rifleman must shoot, it is often advantageous to wait until the target approaches closer before opening fire. Under no circumstances should riflemen open fire on aircraft without orders from an officer (for more details, see below).
Firing When In Combat Operations:
When Under Attack or When Alarm Has Been Given.
During the daytime, the usual fire for riflemen is feu ŕ volonté ("fire-at-will"). Often, however, feu par salves ("volley fire") is also used as it achieves a greater control of fire and has a great effect on both the morale of the enemy and of the men firing. During the night, feu par salves is the rule.
When Attacking an Objective in the Open.
Generally speaking, the riflemen fire as little as possible when engaged in an offensive action, so as to reach the objective as quickly as possible. When firing is done, it is done by a group, ideally by a half-section or section. The half-section or section should fire only for the purpose of protecting the advance of an adjacent formation or to prepare for its own advance. No matter how favorable the opportunities may be, there is no reason for firing if at the same moment advance is possible. It may happen, however, that the advance is impeded by local resistances concentrated at various points (groups of enemy riflemen, machine-guns, etc.). The resistances must be broken as quickly as possible through the effects of group firing, which must be opened without delay.
Special Cases -- Firing on Aircraft:
Soldiers may only open fire on aircraft under the following circumstances:
Detached men or troops who already have an objective to attain (which must not be deviated from) are not permitted to fire on aircraft. If this is not the case and if above requirements have been met, action should be immediately taken, with firing being coordinated by sections.
As the aircraft is flying towards the riflemen, set the sight at 2,400 meters. Face the approaching aircraft and commence firing as soon as it appears at an angle of 45 degrees. Aim straight at it and continue to fire until the aircraft passes vertically overhead. At this point, the riflemen face to the rear toward the departing aircraft and lay down the sights. As the aircraft departs, set the sight at 250 meters, first aiming 10 lengths in advance for approximately 30 seconds. Then aim directly at the aircraft and continue to do so until it reaches an angle of 45 degrees.
The application of these rules assures that the aircraft crosses the cone of fire dispersion once during the approach and twice during the departure. It is useless to fire on an airplane if the spread of its wings are 8 mm, which indicates a distance out of range of rifle fire. It is fire upon landing aircraft.
One way to estimate the distance to a target or objective is by counting paces. Each man must know how many strides he takes to cover a distance of 100 meters. Error is less likely in counting off strides (i.e. counting each time the left foot strikes the ground) than the single pace. Having counted the number of strides which cover 100 meters (normally, 62), make a mark on a piece of paper or place a pebble in your pocket. Then begin counting strides again. To translate the excess over the last 100 strides into meters, it is only necessary to add half that number to the total.
6 pebbles 36 strides = 600 36 18 = 654 meters
This method is also used for sketching.
Through personal observation it is understood that the human face is not visible at 400 meters but the arms can still be seen. At 600 meters, files of men can still be distinguished and that at 1,000 meters, a horse can be distinguished from the cart. Such factors as light, background, dust or terrain features can affect such determinations. Therefore, this method is not very certain but can be improved by allowing several good observers to make their estimations and then averaging these.
Sound travels at 333 meters per second (or 1 km in 3 seconds). Each man should learn to reckon time by mental calculation. If in keeping such time, one starts counting as soon as the flash of a gun discharge is seen, the number reached at the moment of the report will be equal to the number of meters to the gun when multiplied by 333.
4 seconds (between gun flash and gun report) = 1,332 meters