When torrential water tosses boulders, it is because of its momentum. When the strike of a hawk breaks the body of its prey, it is because of timing.

This saying is commonly presented in modern English as a line from Sun Tzu’s *The Art of War*, in the section that discusses “force” and the effective use of energy—often translated as the strategic deployment of momentum (勢, *shi*) and the exploitation of timing and opportunity. In that context, Sun Tzu uses vivid natural analogies (rushing water, a hawk’s strike) to explain how a commander can make decisive outcomes seem effortless by arranging conditions so that power is released at the right moment. However, the exact English wording given here varies across editions and may reflect a paraphrase rather than a fixed canonical translation.

The quote contrasts raw strength with the intelligent orchestration of conditions. Torrential water can move boulders not because it “tries harder,” but because accumulated momentum makes the result inevitable; likewise, a hawk’s kill depends on striking at the precise instant when speed, angle, and vulnerability align. Strategically, Sun Tzu is emphasizing that decisive victory comes from shaping circumstances—positioning, tempo, and psychological advantage—so that force is applied when it will have maximum effect. The deeper implication is that excellence in conflict (or competition) lies in preparation and timing: power is most effective when it is the natural consequence of an arranged situation.