Art of War — 知己知彼

“Know the enemy and know yourself, and you will not be imperiled in a hundred battles” is among the most enduring lines from the *Art of War*, appearing in its third chapter, “Planning Attacks.” It does not promise invincibility, but rather states a condition for sustained safety in conflict: thorough mutual assessment. The passage immediately contrasts this ideal with two lesser conditions—knowing oneself but not the enemy (leading to mixed outcomes), and knowing neither (guaranteeing peril). Classical commentators clarify that “knowing” means concrete, comparative appraisal: weighing political order, leadership quality, troop strength, supply capacity, and terrain on both sides. As Du Mu explains, it is about measuring one’s own situation against the enemy’s across these five dimensions—so that strengths, weaknesses, advantages, and risks become visible before any action begins. Meng Shi adds that such scrutiny reveals the true shape of advantage and danger; Wang Xi defines “dai” (peril) precisely as danger—and stresses that only when both sides are fully understood can victory be anticipated with confidence. Zhang Yu notes this knowledge governs both attack and defense: knowing the enemy enables effective offense; knowing oneself enables sound defense. The line thus anchors a disciplined method—not intuition or willpower, but systematic comparison—as the foundation for resilient decision-making in the *Art of War*.