“The onrush of a conquering force is like the bursting of pent-up waters into a chasm a thousand fathoms deep.”
Accumulated advantage, released at once, is overwhelming; hoard then strike, do not dribble.
Chapter 4’s final image: the onrush of a conquering force is like the bursting of pent-up waters into a chasm a thousand fathoms deep. The verse answers the natural objection to the whole chapter — all this hiding and securing sounds passive. Sun Tzu’s reply is hydraulic: the same water that trickles harmlessly becomes irresistible when released at once, and the depth of the fall is the height of the restraint.
A legal team spends six months in quiet, unglamorous discovery — depositions, documents, expert reports — while the opponent tries the case in the press, leaking daily. The drip-drip wins the news cycle for a season. Then the motion lands: forty exhibits at once, filed together, and the case settles in three weeks. The press strategy had spent itself in dribbles; the waters were banking the entire time.
Pent-up is not held-back-forever — the image is of bursting, not hoarding, and the release must actually come. Teams that accumulate endlessly "until we’re ready" are Chapter 2’s prolonged war wearing Chapter 4’s clothes. The discipline is the pairing: restraint with a defined trigger for release.