THE COMMANDER'S INFLUENCE is shown, first in his orders for the operations, and later by the method in which he employs the forces retained in his hand for the decisive blow. Personal control, by the commander, of troops committed to battle, is not only impossible but should be unnecessary, as such control and leading is the function of his subordinates, who should be fully acquainted with his intentions and must be trusted to carry them into execution. Other, and more important, duties have to be undertaken by the commander, and it is essential that he should not allow his attention to be diverted from his main object by local incidents, which are matters for his subordinates to deal with. "A sound system of command is based upon three facts: an army cannot be effectively controlled by direct orders from headquarters; the man on the spot is the best judge of the situation; intelligent co-operation is of infinitely more value than mechanical obedience" ("The Science of War"). A campaign resolves itself into a struggle between human intelligences. Each commander will endeavour to defeat his adversary in battle, and his principal weapon is his General Reserve. If he can exhaust the reserve power of his adversary, while maintaining his own intact, he can proceed to victory at his own time, and he will endeavour to exhaust the hostile reserves by causing {34} them to be thrown in piecemeal, in ignorance of the spot where the decisive blow is to fall. During the campaign on the Western Front in 1918 the Allies were able to conserve their strength throughout the attacks from March 21 to July 15, and when they passed from the guard to the thrust they extended their front of attack from day to day, calculating correctly that this gradual extension would mislead the enemy as to where the main blow would fall, and would cause him to throw in his reserves piecemeal.