“All armies prefer high ground to low and sunny places to dark.”
Everyone wants the high, lit ground; conceding it hands the opponent the default edge.
Chapter 9 generalizes its terrain rules into preference: all armies prefer high ground to low and sunny places to dark. The verse sounds like it is stating the obvious — and that is its method. Universal preferences define default value. If everyone wants the high sunny ground, then occupying it requires no genius, only refusal to give it away; and conceding it requires no villainy, only casualness.
A company casually cedes the "ground everyone wants" in its market — the flagship conference slot it declines as too expensive, the standard it stops attending because the work was tedious, the search position it drifts from by neglecting docs. None of these feel like surrenders. Three years later a competitor holds all of them, and the market’s default gravity — the preference Sun Tzu named — routes demand to the occupant.
Universal preference is not universal obligation — sometimes the low ground is your strategy (cost position, counter-positioning against the heights), and Chapter 6 blessed flowing around strength. The verse condemns unclaimed-value leakage: ground you wanted, that everyone wanted, conceded through inattention rather than choice. Decide the concession or reverse it; drifting is the only unforgivable option.