Water and Changing Form
Change with the situation
Published July 8, 2026 · By Oriens
夫兵形象水，水之形避高而趋下，兵之形避实而击虚；水因地而制流，兵因敌而制胜；故兵无成势，无恒形，能因敌变化而取胜者，谓之神。
Military disposition resembles water. Water avoids high ground and moves toward low ground; military disposition avoids the full and strikes the empty. Water's flow is shaped by the ground; victory in war is shaped by the enemy. Thus military forces have no fixed configuration and no constant form. One who can change with the enemy and take victory is called skillful beyond measure.
— Sunzi Bingfa · 虚实 (Chapter 6), 夫兵形象水，水之形避高而趨下，兵之形避實而擊虛；水因地而制流，兵因敵而制勝；故兵無成勢，無恒形，能因敵變化而取勝者，謂之神。
The water image makes a conditional point: a method must respond to ground and to the situation. Flexibility is not passivity and not a promise that every change will work. In modern settings, revise a method when evidence changes while keeping obligations and safety constraints visible.
Military disposition resembles water. Water avoids high ground and moves toward low ground; military disposition avoids the full and strikes the empty.
This passage from Xushi (虚实, “Weak Points and Strong”) compares strategic movement to water responding to terrain. It then states that military forces have no fixed configuration or constant form, and that success requires changing with the opponent. The complete displayed range matters: “avoid the full and strike the empty” and “no constant form” are adjacent claims, not interchangeable fragments.
Water is the text’s central image because it combines direction with responsiveness. It does not choose its path at random. Gravity and ground determine where it flows. Sun Tzu applies this to the disposition of forces: shape must follow the contours of the situation, not impose a predetermined pattern upon it. The “skillful beyond measure” commander is one who reads those contours accurately and adapts accordingly.
The original setting is warfare. A modern reader can take from it a discipline of revising methods in response to evidence, but not a license to evade responsibility, treat people as targets, or treat flexibility as moral exemption.
The durable distinction is between purpose and method. A sound purpose may remain steady while the path toward it changes; when circumstances change, the relevant question is not whether to be formless, but which form now fits the situation without hiding harm.