“If we know that the enemy is open to attack, and also know that our men are in condition, but are unaware that the ground makes fighting impracticable, we have still gone only halfway.”
Even with both sides known, ignoring the terrain leaves you at half; the ground is the third leg.
Chapter 10 completes its knowledge triangle: knowing the enemy is open and our men ready, but unaware that the ground makes fighting impracticable — still only halfway. The third leg is terrain, and the verse’s example is deliberate: everything about the two armies was favorable, and the ground alone vetoed the victory. Sun Tzu’s completed model is a triad — force, counterforce, and the field they meet on.
Two companies read each other perfectly — the acquirer knew the target was ready to sell, the target knew the acquirer was ready to buy. Both missed the ground: the regulatory calendar that would stretch approval past both companies’ financing windows. The deal died not on price, readiness, or even intent, but on the terrain neither side had mapped. Every element was green; the field was red.
The triad is complete at three — there is no hidden fourth knowledge that completes victory further. The temptation after learning the triad is to add variables until analysis paralyzes; Sun Tzu adds exactly one term to the classic pair and stops. Self, enemy, ground: enough to decide, and small enough to actually verify.