The best way for artillery to protect itself against annoyance from hostile infantry fire is to push forward an infantry screen, even if only a weak one. In the days when batteries had no shields, this screen enabled artillery to devote its entire attention to the principal target without regard to hostile infantry. At the present time, especially in positions in rear of a crest and in long artillery lines, the principal object of such a screen is to prevent hostile patrols from molesting the artillery. Small detachments posted at wide intervals are sufficient for this purpose. The flanks and rear are now as in the past the vulnerable points and are most exposed to daring, sudden attacks, even if only made by weak hostile detachments. (Par. 448 German I. D. R.). At the battle of =Vionville=,[326] about 5 P. M., four horse and seven field batteries of the IIIrd Army Corps were engaged near =Flavigny= with ten French batteries. After this artillery duel had lasted half an hour, French Guard Infantry advanced to the attack. This was repulsed by artillery fire at a range of 800 m., but the fire of the artillery was diverted from its proper objective by the advance of this infantry. Similarly, at =St. Privat=, two batteries of the Guard Artillery had to direct their fire on French skirmishers. [326] _Gen St. W._, I, p. 557. IX. THE ATTACK. The defense may repulse the enemy, but only the attack can annihilate him. The decision as to whether the force is to attack or stand on the defensive depends upon the tactical situation and the will of the commander, and not upon numerical superiority, of which one is not aware, as a rule, until after the battle.[327] Determined attacks, again and again repeated, in spite of all failures, are the surest means of gaining victory and of preventing the enemy from becoming aware of his superiority. Only pressing reasons (marked hostile superiority, necessity for awaiting approaching reinforcements, or the failure of an attack), and never favorable terrain conditions, should determine a commander to stand on the defensive. In defense the eventual assumption of the offensive is kept constantly in view. A commander who voluntarily stands on the defensive for the purpose of letting the opponent attack, and then attacks him in turn, reaps only the disadvantages and never the advantages of both the offensive and the defensive. [327] See _Taktik_, V, p. 121, et seq.