Strategy classic
Know your enemy and know yourself: what Sun Tzu meant, and how to use it
"Know the enemy and know yourself" is Sun Tzu's rule that safety in a contest comes from knowing both sides, not one. In business you use it as a two-sided assessment: compare your company and one named competitor on the same factors, mark what you don't know, then choose where to compete, where to stay away, and what to find out first.
Short answer
- The line: know both sides and a hundred battles hold no danger; know only yourself and you win one, lose one; know neither and every battle is dangerous (our rendering).
- The point people miss: it promises safety, not victory, and it counts self-knowledge as half the work.
- How to use it: a side-by-side table on the book's five factors, with sources and unknowns, ending in engage, avoid, or learn first.
What the line actually says
The line closes chapter 3 of the Art of War (孫子兵法), the chapter on planning an attack. The original reads:
知彼知己，百戰不殆；不知彼而知己，一勝一負；不知彼不知己，每戰必殆。
Our rendering: know the other side and know yourself, and a hundred battles hold no danger. Know yourself but not the other side, and you win one and lose one. Know neither, and every battle puts you in danger.
Two details matter. First, 殆 means danger or peril. Popular versions turn the first case into "you will win every battle", which the text doesn't say. Knowing both sides keeps you out of fights you misjudged, and sometimes that means not fighting. Second, there are three cases, not one. The middle case is the common one in companies: a team that knows its own product well and guesses about the rival gets a coin flip. The worst case is more common than people admit. Many teams can list a rival's features but can't say why their own customers leave.
The ideas around it
The line is the end of an argument the book builds from its first chapter. Three passages turn it into something you can run.
| Passage | What it says (our summary) | Business reading |
|---|---|---|
| Five factors (道・天・地・將・法), chapter 1 | Weigh the Way (whether people share the leader's aim), heaven (seasons and conditions), ground (distance, ease, width of terrain, and ground where an army lives or dies), the general (wisdom, trust, care, courage, strictness), and method (organization, roles, supplies) | Purpose, timing, terrain, leadership, and how the company runs |
| Seven comparisons, chapter 1 | Whose ruler has the Way, whose general is abler, who holds heaven and ground, whose rules are followed, whose forces are stronger, whose troops better trained, whose rewards and punishments clearer | A scorecard of seven questions, each answered Us, Them, Even, or Unknown |
| Solid and empty, chapter 6 | An army is like water: it avoids high ground and runs to low ground, avoiding what is solid and striking what is empty | Compete where the rival is weak and you are strong; go around their strengths |
Chapter 3 also lists five ways to know who will win. In our rendering: knowing when to fight and when not to, knowing how to use a large or small force, top and bottom wanting the same thing, being prepared against an unprepared opponent, and an able general not overruled by the ruler. These work as a final test of any plan to compete.
Who should use it
Founders, product leads, and marketers facing one rival that keeps showing up in deals, reviews, or customer conversations. It also helps before entering a segment where someone is already established, or before a price or launch decision a rival will answer.
It's the wrong tool for judging whether a whole industry is worth entering; that's Porter's five forces. It's also more than a sales battlecard: a card tells reps what to say on a call, while this assessment decides where the company competes at all.
How to run the assessment
- Name the contest and the decision. Write which customers both sides compete for and what this work will decide, in one sentence each.
- Collect facts on both sides with sources. Tag each fact by where it came from (their site, reviews, your win-loss notes, internal data) and date it. Gather the same kinds of facts about yourself as about them.
- Fill the five factors side by side. For purpose, timing, terrain, leadership, and method, write what you know about each side and who has the edge. Write "unknown" where you don't know.
- Answer the seven comparisons. Rewrite each question for your market, such as "whose team ships more reliably", and mark Us, Them, Even, or Unknown with a source.
- Grade your knowledge. Count the unknowns on each side and say which of the three cases you're in: you know both sides, only yourself, or neither.
- Map their solid and empty points. List the rival's proven strengths and its gaps. Pair each gap with a strength of yours that has evidence; drop gaps you can't fill.
- Decide engage, avoid, or learn first. Engage where their gap meets your strength. Avoid their strong ground. Mark openings that rest on unknowns as learn first, then test the plan against the five conditions for victory.
- Write the learning plan. List the top unknowns that would change the decision, how to find each out, an owner, and a date, plus a date to review the decision.
A worked mini example
An illustration, not a real company. Pantry Ledger sells inventory software to independent cafés for $29 a month. Its rival, StockStack, charges $49 and offers supplier ordering, which Pantry Ledger lacks. Pantry Ledger won 7 of 9 deals against StockStack at single-site cafés and lost 4 of 5 at three-site cafés, each time over supplier ordering. Six of StockStack's last 20 reviews complain about slow support. Pantry Ledger has 6 staff and 18 months of runway; StockStack has about 40 staff.
The table shows the edge split by terrain: single-site cafés are Pantry Ledger's ground, three-site cafés are StockStack's. Supplier ordering is StockStack's solid point; price and support speed look empty. The grading step shows a surprise: Pantry Ledger doesn't know why its own customers churn, so it is closer to "knows neither" than it thought. The decision: don't build supplier ordering this quarter, compete on price and support at single-site cafés, and call the last 8 churned customers before the next review.
Common mistakes
- Studying only the rival. Half the table is about you, and it's usually the half with more unknowns.
- Treating the line as a promise of victory. The text promises you won't be caught out. Choosing not to fight is a valid result.
- Filling gaps with impressions. "They're probably slow" goes in as unknown, with a way to check it.
- Attacking the most visible strength. The feature everyone talks about is often the rival's high ground.
If the team is reacting to a rival's announcement rather than planning, step back first with a wide-view situational review. To check how your strengths hold up on their own, see SWOT and TOWS.
Where it comes from
The Art of War is traditionally attributed to Sun Wu, Master Sun, a general of the late Spring and Autumn period (traditional dates 544–496 BCE); a Ritsumeikan University scholar dates the ideas it reflects to about the 5th century BCE. Scholars disagree on its date and author. Many place the text in the Warring States period, and the same scholar describes it as the work of a school centered on Sun. The Chinese text is public domain. Every English rendering on this page is our own, made from the original, and this page is an independent summary, not a translation of any edition.
Questions
What does "know your enemy and know yourself" mean?
It's from chapter 3 of Sun Tzu's Art of War. If you know both the other side and yourself, you won't be put in danger however many times you fight; know only yourself and your odds are even; know neither and every fight is dangerous.
Does Sun Tzu say you will win every battle?
No. The original says 不殆, "no danger", not "victory". The point is that you won't stumble into a fight you misjudged, and that includes knowing when not to fight.
How do you apply it to business competition?
Compare your company and one named rival on the same factors, with a source for every fact and the gaps marked unknown. Then engage where their weak point meets your strength, avoid their strong points, and learn the unknowns that would change the decision.
Free AI skill
Use this as an AI skill
The Know the enemy and yourself skill turns this method into steps your AI follows. Compares you and one named competitor on Sun Tzu's five factors and seven comparisons, marks every unknown, then picks where to engage, where to avoid, and what to learn first.
Works in Claude, ChatGPT, and coding agents. In a pod, everyone on your team runs the same version.
Sources
- 孫子兵法, original Chinese text (Wikisource) — chapters 1, 3 and 6: the five factors, seven comparisons, five conditions for victory, the know-the-enemy line, strong and weak points (read 2026-11-04)
- Ritsumeikan University, College of Letters: column by Ishii Mamiko on the Sunzi — attributed to a school around Master Sun; reflects late Spring and Autumn thought (about the 5th century BCE) (read 2026-11-04)
- The Art of War, Literary Themes for Students (Gale), on Encyclopedia.com — Sun Wu's traditional dates (544–496 BCE); authorship debate; most scholars place the text in the Warring States period (read 2026-11-04)