The weakness of most defensive positions lies in the danger of a sudden attack being directed against a flank. The assailant will endeavor to avoid making an attack against the front of a position prepared for defense, when such an attack has small chances of succeeding, and seek the decision by attacking a flank, where conditions are, to a certain extent at least, equalized. The danger of a flank attack increases with the length of the defensive line. It is by no means a good move to prolong the threatened wing (French VIth Army Corps at St. Privat) for the purpose of warding off an envelopment. The power of extension is bound to reach a limit sooner or later, and the wing attacked will then be so weak and attenuated that it will not be capable of offering serious resistance.
To ward off an employment by refusing a flank likewise promises little success. The enemy's superiority of fire will make itself felt, first of all, at the salient thus formed (see p. 357 supra), and his convergent artillery and infantry fire, which may even enfilade parts of the line, will paralyze all tactical movements of the defender at this point.
By prolonging the line and by refusing a flank, we only postpone the decision a little while, but cannot effectively cope with an envelopment. This must be accomplished in a different manner.
The best scheme would be to flank the enemy's enveloping force by posting an echelon in a suitable position, or to bring about a decision by employing the reserve offensively. However, for carrying out these measures, more time is required than for merely refusing a flank. Time may be gained by making an extensive reconnaissance on the flanks with strong detachments, and by occupying supporting points lying on the flanks, which the enemy would have to take before he could think of attacking the main position.
In employing machine guns in defense, it should be borne in mind that they are unsuited for carrying on protracted fire
