鄉間 is the emended reading of Chia Lin and the _T‘u Shu_ for the
unintelligible 因間, here and in § 7, of the standard text, which
nevertheless reads 鄉間 in § 22.
means employing the services of the inhabitants of a district.
Tu Mu says: “In the enemy’s country, win people over by kind
treatment, and use them as spies.”