“Attack him where he is unprepared, appear where you are not expected.”
The advantage goes to whoever chooses the time and place of the contest. Act where the other side is unprepared and where they do not expect you — and you force them to fight on your terms.
The final line of Chapter 1’s stratagem catalogue — 攻其无备，出其不意 — and the bridge into everything that follows. Having listed the deceits and the baits, Sun Tzu states their shared purpose: arrive unopposed because you arrived unlooked-for. The whole chapter about calculation ends on the operational payoff of all that preparation: you, not the enemy, hold the pen that writes when and where.
An indie author cannot win the bookstore endcap, so she does not contest it. She launches where publishers are structurally absent — a niche community whose podcast ad slots cost less than one endcap poster — and arrives there with a book written for that audience specifically. The publisher’s sales team never sees the attack; the category’s numbers simply rearrange themselves one quarter.
Being unexpected is not the same as being sneaky toward customers — the surprise belongs to competitors, not to the people you serve. And the trick decays with use: the second author in that podcast is now expected, and the advantage is gone. Sun Tzu’s phrase implies motion — you keep choosing fresh ground, because yesterday’s surprise is today’s battlefield.