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

30. Asked if an army can be made to imitate the _shuai-jan_,

[That is, as Mei Yao-ch’en says, "Is it possible to make the front and rear of an army each swiftly responsive to attack on the other, just as though they were part of a single living body?"] I should answer, Yes. For the men of Wu and the men of Yüeh are enemies; [Cf. VI. § 21.] yet if they are crossing a river in the same boat and are caught by a storm, they will come to each other’s assistance just as the left hand helps the right. [The meaning is: If two enemies will help each other in a time of common peril, how much more should two parts of the same army, bound together as they are by every tie of interest and fellow-feeling. Yet it is notorious that many a campaign has been ruined through lack of cooperation, especially in the case of allied armies.]