17. 軍旁有險阻蔣潢井生葭葦小林蘙薈必謹覆索之此伏姦之所藏處也
If in the neighbourhood of your camp
The original text has 軍行, but 旁 has been generally adopted as yielding much better sense.
there should be any hilly country,
險阻 is 邱阜之地, according to Chang Yü.
ponds surrounded by aquatic grass, hollow basins filled with reeds,
The original text omits 蔣 and 生, so that 潢 and 井 join to make a pair: “ponds and basins.” This is plausible enough at first sight, but there are several objections to the reading: (1) 蔣 is unlikely to have got into the text as a gloss on 潢; (2) it is easy to suppose, on the other hand, that 蔣 and afterwards 生 (to restore the balance of the sentence) were omitted by a copyist who jumped to the conclusion that 潢 and 井 must go together; (3) the sense, when one comes to consider it, actually requires 蔣, for it is absurd to talk of pools and ponds as in themselves suitable places for an ambush; (4) Li Ching (571–649 A. D.) in his 兵法 “Art of War” has the words: 蔣潢蘙薈則必索其伏. This is evidently a reminiscence of Sun Tzŭ, so there can be little doubt that 蔣 stood in the text at this early date. It may be added that the T‘ung Tien and Yü Lan both have 蔣, and the latter also reads 并 for 井.
or woods with thick undergrowth,
I read 小林 with the Yü Lan in preference to 山林, given in the original text, which is accepted by the commentators without question. The text of the T‘u Shu up to this point runs as follows: 潢井蒹葭林木蘙薈者.
they must be carefully routed out and searched; for these are places where men in ambush or insidious spies are likely to be lurking.