Hence the saying: 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.
Note
A great military strategist and thinker in ancient China, who lived in the late Spring and Autumn Period. He authored The Art of War, the world’s earliest and most influential military classic. His strategic thoughts have been widely applied in military, politics and management worldwide.
Know the enemy and know yourself
The most famous maxim of The Art of War. It emphasizes intelligence gathering and self-assessment.
Avoid danger in battles
It means taking proper actions based on full understanding to defeat risks.
Intelligence awareness
A basic requirement for commanders and decision-makers in ancient wars and diplomacy.
The Battle of Changshao: A Masterclass in “Know the Enemy, Know Yourself”
The Battle of Changshao (684 BC), fought between the states of Qi (larger, stronger) and Lu (smaller, weaker) during the Spring and Autumn period, is a perfect historical illustration of Sun Tzu’s principle. This battle is famously recorded in the Zuo Zhuan (Commentary of Zuo).
Here is an analysis of how Cao Gui, the advisor to the Duke of Lu, applied the logic of Chapter 3.6 to secure a victory against a numerically superior foe.
Knowing the Enemy: Exploiting the Psychology of the Opponent
The State of Qi launched a large-scale invasion of Lu. The Duke of Lu prepared to mobilize his troops immediately. However, Cao Gui intervened, instructing the Duke to wait.
The Principle: “If you know the enemy and know yourself, you need not fear the result of a hundred battles.”
Cao Gui understood the psychology of the Qi army. He knew that:
- The Qi soldiers were overconfident due to their superior numbers and the reputation of their state.
- Their morale (“Qi”) would be high at the beginning (“First the morale is high”) but would wane if the attack was delayed.
Cao Gui ordered the Lu troops to stay behind their fortifications and refuse battle during the first two Qi assaults. He was waiting for the enemy’s momentum to peak and then collapse.
Knowing Yourself: Understanding Your Limitations
The Duke of Lu was eager to fight, but Cao Gui recognized the reality of their situation.
The Principle: Self-assessment.
Cao Gui knew that the Lu army, while brave, could not match the Qi army in a head-on clash during the enemy’s peak morale. Instead of relying on brute force, he leveraged the strength of defense and the terrain.
By holding the line and absorbing the enemy’s attacks without breaking, the Lu army conserved its energy while the enemy exhausted theirs.
The Decisive Moment: “One Victory, One Defeat” vs. “No Danger”
When the Qi army launched its third assault, it was disorganized and tired. Cao Gui saw that the “time” was right.
The Principle: “If you know yourself but not the enemy, for every victory gained you will also suffer a defeat.”
A lesser general might have fought earlier (risking a 50/50 chance), but Cao Gui waited for a moment of near-certainty.
Cao Gui ordered a counter-attack. The fresh Lu troops smashed into the weary Qi forces, routing them completely. Furthermore, Cao Gui stopped the Duke from pursuing immediately, fearing an ambush. He inspected the enemy’s wheel tracks and observed their flags to confirm they were truly retreating in panic before ordering a pursuit.
Conclusion
The Battle of Changshao is a textbook example of Sun Tzu’s teaching in action. Cao Gui demonstrated perfect “intelligence awareness” by predicting the enemy’s psychological trajectory (their morale rising and falling like a tide). He combined this with “self-assessment,” recognizing his army’s need to fight defensively first.
By adhering to the rule – knowing both the enemy and himself – Cao Gui achieved a decisive victory without “danger”, turning a seemingly defensive situation into a total rout of a stronger enemy. This battle proves that information and timing are more powerful than numbers alone.
故曰：知彼知己，百戰不殆；不知彼而知己，一勝一負；不知彼，不知己，每戰必敗。
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