If you know the enemy and know yourself, you need not fear the result of a hundred battles. If you know yourself but not the enemy, for every victory gained you will also suffer a defeat. If you know neither the enemy nor yourself, you will succumb in every battle.

This maxim is attributed to Sun Tzu’s ancient Chinese military treatise The Art of War, traditionally dated to the late Spring and Autumn period (often placed around the 5th century BCE), though the text’s compilation history is complex. The line appears in the chapter commonly translated as “Laying Plans” (or “Initial Estimations”), where Sun Tzu argues that victory is largely determined before fighting begins—through intelligence, assessment, and strategic calculation. In this setting, “knowing” refers not only to spying on an opponent but also to soberly appraising one’s own capabilities, morale, logistics, leadership, and constraints. The passage reflects a broader emphasis in the work on foreknowledge, deception, and avoiding avoidable battles.

The quote frames success as a function of comparative understanding: accurate self-knowledge and accurate knowledge of the opponent. “Know yourself” implies recognizing strengths, weaknesses, resources, and limits; “know the enemy” implies intelligence about the adversary’s intentions, capacities, and vulnerabilities. The middle case—self-knowledge without enemy knowledge—warns that internal competence cannot compensate for strategic blindness: one may win some engagements yet be surprised into losses. The final case describes total ignorance as systemic failure. Beyond warfare, the passage has been widely applied to politics, business, and personal decision-making as an argument for disciplined assessment and information-gathering before committing to high-stakes action.