The value of the negative corpus

“There are no two ways about it—patrols are the eyes of the small infantry unit. Sometimes these patrols will discover just where the enemy is and just what he is doing. This, of course, is information of the highest value. But more often than not, they will bring in only negative information; they will report that the enemy is not in such-and-such a place and is not doing this, that, or the other thing. To the intelligent leader, information of this type is frequently of the greatest importance and he will impress that fact on his patrols. As for the leader himself, he must never lose sight of the value of patrols nor allow this important duty to degenerate into a routine, slipshod, you-do-it-sergeant affair. Since the success of a battalion, a regiment, or even a division, will frequently depend on the conduct of one small patrol, patrols must be hand-picked, carefully instructed, and given a clear, definite mission. These three things play a vital part in the borderland between success and failure.” – George C. Marshall, Infantry in Battle