It will frequently be necessary to send forward a thin skirmish line in order to induce the enemy to open fire and reveal his position.
394. It will frequently be impossible to obtain satisfactory information until after the action has begun. The delay that may be warranted for the purpose of reconnaissance depends upon the nature of the attack and the necessity for promptness. For example, in a meeting engagement, and sometimes in a holding attack, the reconnaissance may have to be hasty and superficial, whereas in an attack against an enemy carefully prepared for defense there will generally be both time and necessity for thorough reconnaissance.
395. In defense, reconnaissance must be kept up to determine the enemy's line of advance, to ascertain his dispositions, to prevent his reconnaissance, etc.
Patrols or parties posted to prevent hostile reconnaissance should relieve the main body of the necessity of betraying its position by firing on small bodies of the enemy.
396. Reconnaissance continues throughout the action.
A firing or skirmish line can take care of its front, but its flanks are especially vulnerable to modern firearms. The moral effect of flanking fire is as great as the physical effect. Hence, combat patrols to give warning or covering detachments to give security are indispensable on exposed flanks. This is equally true in attack or defense.
397. The fact that cavalry patrols are known to be posted in a certain direction does not relieve infantry commanders of the responsibility for reconnaissance and security.
To be surprised by an enemy at short range is an unpardonable offense.
398. The commander of a battalion on a flank of a general line invariably provides for the necessary reconnaissance and security on that flank unless higher authority has specifically ordered it. In any event, he sends out combat patrols as needed.
Where his battalion is on a flank of one section of the line and a considerable interval lies between his battalion and the next section, he makes similar provision.
399. Battalion commanders in the first line establish patrols to observe and report the progress or conduct of adjoining troops when these can not be seen.
400. In a decisive battle success depends on gaining and maintaining fire superiority. Every effort must be made to gain it early and then to keep it.