The original meaning of bing 兵 is "weapon." From this it comes to mean soldier, army, war and, most generally, the military.
A well-known passage from the Zuozhuan, dating traditionally to 578 B.C., reads: "The great matters of the state lie in sacrifice and arms (rong 戎)(Duke Ch'eng, year 13, cf. James Legge, The Confucian Classics , vol. 5, The Ch'un Ts'ew with the Tso Chuen [Taiwan reprint, n.d.], p. 382). What is the relationship of these two passages? Is the Sunzi rewriting the Zuozhuan text? Are the passages quite independent? This kind of question rarely has a simple answer with Warring States period texts. Although the writing of the Zuozhuan is a late fourth-century enterprise, it unquestionably preserves (and rewrites) much earlier materials. (For the earliest version of this argument, see Bernard Karlgren, "On the Authenticity and Nature of the Tso Chuan ," Goteborgs Hogskolas Aorsskrift 32 [1926]. For a case study, see Kidder Smith, " Zhouyi Divination from Accounts in the Zuozhuan ," Harvard Journal of Asiatic Studies 49.2 [1989], pp. 421-63, especially "Using the Zuozhuan Evidence," pp. 455-59.) The Sunzi that we possess today was probably edited about the same time as the Zuo, yet it also certainly preserves earlier traditions. Who is borrowing from whom?
It would be attractive to argue that the Sunzi is deliberately altering a famous text, eliminating the sacrificial function and preserving only the military (bing 兵) as the essential matter (or service, shi 事) of the state. In abbreviated form this reflects the historical development set out in Mark Edward Lewis's important book, Sanctioned Violence in Early China (Albany: State University of New York Press, 1990). Yet the relationship between military force and the state is a central question in most societies, and one that was felt keenly by all Warring States thinkers. For example, the Guanzi offers a parallel statement, saying, "That which the enlightened king . . . gives weight to is government in conjunction with the army" (zheng yu jun 正與軍, in "Bayan" 霸言 [Conversations of the Lord Protector], section 23, Guanzi [Shanghai: Shanghai guji, 1989], p. 87b; cf. Allyn Rickett, tr., Guanzi , vol. 1 [Princeton: Princeton University Press, 1985], p. 358). Thus while the Sunzi editor may well be deliberately playing on an ancient phrase from the Zuozhuan, it is essential to acknowledge the widespread sharing of common terms and concerns within the Warring States oral and literate traditions. For this reason a weaker, non-causal connection between these texts is equally plausible.