periority is essential. To gain this, two things are necessary: A
heavy fire and a fire well-directed and controlled. Both of these are
best obtained when the firing line is as dense as practicable, while
leaving the men room for the free use of their rifles.

If the men are too widely separated, direction and control are very
difficult, often impossible, and the intensity of fire is slight in
proportion to the front occupied. (432)

=447. Density of 1 man per yard; occupation of only sections of long
lines.= In an attack or stubborn defense the firing line should have a
density of one man per yard of front occupied.

Where the tactical situation demands the holding of a line too long to
be occupied throughout at this density, it is generally better to
deploy companies or platoons at one man per yard, leaving gaps in the
line between them, than to distribute the men uniformly at increased
intervals. (433)

=448. Use of thin firing line.= A relatively thin firing line may be
employed when merely covering the movements of other forces; when on
the defensive against poor troops; when the final action to be taken
has not yet been determined; and, in general, when fire superiority is
not necessary. (434)

=449. Length of firing line employed by whole force; strength of
supports and reserves; density of charging line.= The length of the
firing line that the whole force may employ depends upon the density
of the line and the strength in rear required by the situation.

Supports and reserves constitute the strength in rear.

In a decisive attack they should be at least strong enough to replace
a heavy loss in the original firing line and to increase the charging
line to a density of at least one and one-half men per yard and still
have troops in rear for protection and for the other purposes
mentioned above. (435)

=450. Strength of reserve; troops deployed varying from 1 to 10 men
per yard.= In the original deployment the strength of the reserve held
out by each commander comprises from one-sixth to two-thirds of his
unit, depending upon the nature of the service expected of the
reserve.

A small force in a covering or delaying action requires very little
strength in rear, while a large force fighting a decisive battle
requires much. Therefore, depending upon circumstances, the original
deployment, including the strength in rear, may vary from 1 to 10 men
per yard. Against an enemy poorly disciplined and trained, or