“All warfare is based on deception.”
Strategy depends partly on managing what an opponent believes about intentions, strength, timing, and position rather than revealing every fact directly.
Source details
The Art of War, Chapter I 'Laying Plans,' section 18, Lionel Giles translation (1910), original scan leaf 62. 'All warfare is based on deception' begins Giles's section 18 before the examples of seeming unable, inactive, near or far. This remains translation-mediated ancient military strategy, not generic business, relationship or current operational advice.