Themes
Water shapes its course according to the nature of the ground over which it flows; the soldier works out his victory in relation to the foe whom he is facing.
— Sun Tzu · The Art of War

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The passage compares a soldier's response to an opponent with water following the shape of the ground. Both images emphasise adjustment to particular conditions. Victory is presented as relational, worked out against the foe actually faced, rather than treated as independent of the situation.
Context reviewed