It keeps down the fire of the hostile artillery and seeks to
neutralize the hostile infantry by inflicting losses upon it,
destroying its morale, driving it to cover, and preventing it from
using its weapons effectively.

In defense, it ignores the hostile artillery when the enemy's attack
reaches a decisive stage and assists in checking the attack, joining
its fire power to that of the defending infantry.

422. Troops should be accustomed to being fired over by friendly
artillery and impressed with the fact that the artillery should
continue firing upon the enemy until the last possible moment. The
few casualties resulting from shrapnel bursting short are trifling
compared with those that would result from the increased effectiveness
of the enemy's infantry fire were the friendly artillery to cease
firing.

Casualties inflicted by supporting artillery are not probable until
the opposing infantry lines are less than 200 yards apart.

423. When the distance between the hostile infantry lines becomes so
short as to render further use of friendly artillery inadvisable, the
commander of the infantry firing line, using a preconcerted signal,[3]
informs the artillery commander. The latter usually increases the
range in order to impede the strengthening of the enemy's foremost
line.

[Footnote 3: With a 4-foot white and red regimental signal flag.]

_Fire of Position._

424. Infantry is said to execute fire of position when it is posted so
as to assist an attack by firing over the heads, or off the flank, of
the attacking troops and is not itself to engage in the advance; or
when, in defense, it is similarly posted to augment the fire of the
main firing line.

Machine guns serve a like purpose.

In a decisive action, fire of position should be employed whenever the
terrain permits and reserve infantry is available.

DEPLOYMENT.

425. Troops are massed preparatory to deployment when the nature of
their deployment can not be foreseen or it is desirable to shorten the
column or to clear the road. Otherwise, in the deployment of large
commands, whether in march column, in bivouac, or massed, and whether
forming for attack or for defense, they are ordinarily first formed
into a line of columns to facilitate the extension of the front prior
to deploying.

The rough line or lines of columns thus formed enable troops to take
advantage of the terrain in advancing and shorten the time occupied in
forming the f