Use the reserve only when needed or when a favorable opportunity for its use presents itself. Keep some reserve as long as practicable, but every man that can be used to advantage must participate in the decisive stage of the combat. Flanks must be protected either by reserves, fortifications, or the terrain. Flank protection is the duty of the commanders of all flank units down to the lowest, whether specifically enjoined in orders or not. This applies to units on both sides of gaps that may exist in the combat lines.
Reconnaissance continues throughout the action.
The purely passive defense is justified where the sole object is to gain time, or to hold certain positions pending the issue of events in other parts of the field. Its results, when it accomplishes its mission, can never be other than negative. The basic principles of the combat tactics of the different arms are set forth in the drill regulations of those arms for units as high as brigades. It is the function of higher troop leading to so combine and coordinate the combat tactics of all the arms as to develop in the combined forces the teamwork essential to success. While the fundamental principles of war are neither very numerous nor complex, their application may be difficult and must not be limited by set rules.