Employing our whole force at one time in order to gain advantage over the enemy, we may not have time enough to gain our object. If we push on with a portion of the force only, the transport is lost. Discarding helmet and armour; stopping neither day nor night; marching double distance; doing double work; and finally contending with the enemy at a distance of a hundred leagues: results in the loss of the general. Since the strong men arrive first, and the tired drop in rear, only one-tenth of the forces is available. A forced march of fifty leagues to secure an advantage may result in failure to the leader of the vanguard, for only half his men will arrive. After a forced march of thirty leagues to secure an advantage, only two-thirds of the army will be available. Further, a lack of ammunition, of supplies, or of stores, may lead to disaster. The ruler who is ignorant of the designs of neighbouring princes, cannot treat with them. He who is ignorant of mountain and forest, defile and marsh, cannot lead an army. He who does not employ a guide, cannot gain advantage from the ground. Disguise your movements; await a favourable opportunity; divide or unite according to circumstance. Let your attack be swift as the wind; your march calm like the forest;[12] your occupation devastating as fire. In defence, as a mountain rest firm; like darkness impenetrable to the enemy. Let your movements be swift as the lightning. Let as many as possible take part in the plunder: distribute the profit from the captured territory. So he who understands the crooked and the straight way conquers. These are the methods of Battle Tactics. According to the ancient books on war, the drum and bell are used, because the voice does not carry; the flag is used to assist the sight. The use of bell, drum, banner and flag is to attract the united attention of eye and ear. When all are united, the strong are not left to go forward alone, the cowardly are not free to retreat unrestricted. In this way can a multitude be used. Therefore in night fighting, beacons and drums are largely used; in day fighting, a great number of banners and flags and the enemy's eyes and ears are confounded. We thus awe his army, and defeat his general's ambition. In the morning the spirits are keen; at midday there is a laziness; in the evening a desire to return. Wherefore, he who uses his soldiers well, avoids the time when the spirits are keen; but attacks the enemy when he is languid or seeking his camp. Thus should the nature of energy be turned to account. To oppose confusion with order, clamour with quiet, is to have the heart under control. To await an enemy from a distance, to oppose hunger with satiety, rest with fatigue, is the way to husband strength. Do not attack where lines of banners wave, nor the serried ranks of battle spread, but patiently await your time.