=4. Object of Overlapping the Sectors.=--The overlapping of sectors insures that the entire front is kept under close observation, and that no part of it remains unswept by fire should occasion arise for delivering fire at a target in any part. It also prevents waste of ammunition and loss of fire effect through units firing at objectives outside their own sectors unless this is necessary for the purpose of mutual support.
=5. Example of Field of Fire divided into Sectors.=--(i) Fig. 47 shows a field of fire divided into overlapping sectors by the use of description points. The sketch illustrates the arrangements made, as the result of a hasty preliminary reconnaissance, by a company commander for fire action by the four sections or normal fire-units of his command on deployment in the early stage of attack. In defensive positions similar arrangements may be made for indicating sectors allotted to each locality. Defensive positions will usually include a number of localities of special tactical importance. From these localities either direct or flanking fire, or both, is brought to bear on all ground over which the enemy may advance. As long as this is done the intervening ground between localities need not be held in a continuous line.
(ii) In defence, the arrangements for fire action will include the various measures described in Chapter VIII of _Field Entrenchments_ of this series, such as clearing the foreground of features which would afford cover to the enemy and assist his advance, and clearing it of features to improve the defenders field of fire, together with the construction of different obstacles to impede and check the enemy’s advance or cause him to select lines of approach along avenues commanded by the fire of the defenders.
=6. Direction and Control of Fire.=--Fire is said to be _directed_ by the commander, who defines the objective against which it is to be used, and to be _controlled_ by the fire-unit commanders, who give the necessary executive words of command. In attack occasions will frequently arise when fire-unit commanders must both direct and control the fire of their units, while at close ranges, or when men are widely extended, it may happen that the transmission of any fire-order is impossible, and that each individual man must control his own fire.