Tao te Ching

31 Weapons of war are instruments of disaster. They are rejected by all beings. Thus a person of Tao will not dwell upon them. According to the ancient custom of Ying and Yang, A man of virtue values the left which is represented by Yang. And a man of war values the right which is represented by Ying. Weapons are instruments of evil, and are not valued by a man of virtue. They are only used as the last resort to attain peach when all else have failed. If their use is necessary, it is best to employ with calmness and tranquility. Even it if means victory, it is not something pleasant. Those who rejoice over the victory, enjoy killing. He who delights in killing will not be favored by the people and shall not bring harmony to the world. It is the ancient custom to favor happy events to the left as represented by yang. While on sad occasions, it is favored to the right as represented by Ying. When this rite is applied in the army, The lieutenant general takes the place of the left, And the commander-in-chief takes the place of the right. This indicates that war is treated as if it is a funeral service; For many lives had been killed and hence should be mourned with sorrow. Therefore, although a victory was won, It is treated like funeral rite.