[509.] If a night attack or close approach by the enemy is expected, troops in a prepared position should strengthen the outguards and firing line and construct as numerous and effective obstacles as possible. Supports and local reserves should move close to the firing line and should, with the firing line, keep bayonets fixed. If practicable, the front should be illuminated, preferably from the flanks of the section.
[510.] Only short range fire is of any value in resisting night attacks. The bayonet is the chief reliance. (See [Night Operations].)
COUNTERATTACK.
[511.] The passive defense should be assumed only when circumstances force it. Only the offensive wins.
[512.] An active defense seeks a favorable decision. A favorable decision can not be expected without counterattack.
[513.] A passive defense in a position whose flanks are not protected by natural obstacles is generally out of the question.
[514.] Where the defense is assumed with a view to making a counterattack, the troops for the counterattack should be held in reserve until the time arrives for such attack. The defensive line should be held by as few troops as possible in order that the force for the offensive may be as large as possible.
The force for the counterattack should be held echeloned in rear of the flank which offers it the greatest advantage for the proposed attack.
[515.] The counterattack should be made vigorously and at the proper time. It will usually be made:
By launching the reserve against the enemy's flank when his attack is in full progress. This is the most effective form of counterattack.