This passage introduces four ways to probe enemy intelligence: analyzing schemes, provoking movements, feigning deployments and small skirmishes. The supreme stratagem is invisible troop formations, hiding all plans and flexibly adapting tactics to endless shifting battlefield conditions.
This part presents Sun Tzu’s famous maxim. Knowing both the enemy and yourself guarantees safety in all battles. Knowing only yourself leads to mixed results, while ignorance of both sides will bring certain defeat in every fight.