ll be of great value in assisting their own
advance, or in checking the advance of the enemy, and will have
considerable time to operate before hostile artillery fire can silence
them.

Care must be taken not to leave them too long in action. (539)

=554. Use of machine guns with rear guard.= They are valuable to a
rear guard which seeks to check a vigorous pursuit or to gain time.
(540)

=555. Machine guns in attack; fire of position.= In attack, if fire of
position is practicable, they are of great value. In this case fire
should not be opened by the machine guns until the attack is well
advanced. At a critical period in the attack, such fire, if suddenly
and unexpectedly opened, will greatly assist the advancing line. The
fire must be as heavy as possible and must be continued until masked
by friendly troops or until the hostile artillery finds the machine
guns. (541)

=556. Machine guns in defense.= In the defense, machine guns should be
used in the same general manner as described above for the attack.
Concealment and patient waiting for critical moments and exceptional
opportunities are the special characteristics of the machine-gun
service in decisive actions. (542)

=557. Machine guns as part of reserve; use in covering withdrawal.= As
part of the reserve, machine guns have special importance. If they are
with the troops told off to protect the flanks, and if they are well
placed, they will often produce decisive results against a hostile
turning movement. They are especially qualified to cover a withdrawal
or make a captured position secure. (543)

=558. Machine guns not to form part of firing line of attack.= Machine
guns should not be assigned to the firing line of an attack. They
should be so placed that fire directed upon them is not likely to fall
upon the firing line. (544)

=559. Effectiveness of machine guns against skirmish line, except when
lying down or crawling.= A skirmish line can not advance by walking or
running when hostile machine guns have the correct range and are ready
to fire. Machine-gun fire is not specially effective against troops
lying on the ground or crawling. (545)

=560. Silencing of machine guns by infantry.= When opposed by machine
guns without artillery to destroy them, infantry itself must silence
them before it can advance.

An infantry command that must depend upon itself for protection
against machine guns should concentrate a large number of rifles on
each gun