The Art of War by active 6th century B.C. Sunzi

2. Having collected an army and concentrated his forces, he must blend

and harmonise the different elements thereof before pitching his camp. ["Chang Yu says: "the establishment of harmony and confidence between the higher and lower ranks before venturing into the field;" and he quotes a saying of Wu Tzŭ (chap. 1 ad init.): "Without harmony in the State, no military expedition can be undertaken; without harmony in the army, no battle array can be formed." In an historical romance Sun Tzŭ is represented as saying to Wu Yuan: "As a general rule, those who are waging war should get rid of all the domestic troubles before proceeding to attack the external foe."]