27. Hence it is only the enlightened ruler and the wise general who will use the highest intelligence of the army for purposes of spying and thereby they achieve great results.
[Tu Mu closes with a note of warning: "Just as water, which carries a boat from bank to bank, may also be the means of sinking it, so reliance on spies, while production of great results, is oft-times the cause of utter destruction.">[
Spies are a most important element in war, because on them depends an army’s ability to move.
[Chia Lin says that an army without spies is like a man without ears or eyes.]
[1] "Aids to Scouting," p. 2.
[2] "Marshal Turenne," p. 311.