Spirit

The means by which the commanding general wages warfare is his soldiers; the means by which the soldiers engage in combat is their ch'i (spirit). The means by which ch'i proves victorious is the beating of the war drums. Since the drums are capable of inciting the ch'i of the officers and troops, they should not be incessantly employed. If employed too many times, the soldiers' ch'i will easily decline. Similarly, they cannot be employed when too far away from the enemy. If too far, the soldier's strength will easily be exhausted. You must estimate when the enemy will be within sixty or seventy paces and then beat the drums to signal the officers and troops to advance into combat. If the enemy's ch'i abates while yours surges, their defeat will be certain. A tactical principle from the Wei Liao-tzu states: "When their ch'i is substantial they will fight; when their ch'i has been snatched away they will run off."