The Army on the March — The Art of War

Chapter 9 is Sun Tzu's field manual. It covers two things with precision: how to move through different terrain, and how to read what an enemy is doing from observable signs.

Part one: terrain rules. Each environment demands a different approach:

1. Mountains , keep to valleys, stay close to slopes with vegetation, camp on high ground but never try to hold the heights by ascending to meet an enemy already above you. 2. Rivers , after crossing, get far away from the water immediately. If the enemy is crossing toward you, don't meet them in the water , wait until they're halfway across, then strike. 3. Marshes and wetlands , cross quickly and without hesitation. Do not encamp in salt marshes. If forced to fight there, stay close to water and grass. 4. Open flat ground , take positions with easy access, keep high ground to your right and rear. This puts natural advantage behind you.

Part two: reading signals. Sun Tzu catalogues the observable signs that betray enemy intentions , a complete intelligence system built on observation:

- Dust rising high in columns may mean chariots advancing - Dust low and spreading wide may mean infantry on the move - Dust rising in scattered patches may mean soldiers gathering firewood - Birds suddenly rising from a spot may mean troops hidden beneath - Beasts startled and fleeing may mean the enemy is advancing under cover - Tame words from a position of strength may mean the enemy is preparing to advance - Humble words with increased preparations may mean attack is imminent - Violent language followed by apparent retreat may mean a feint, not a withdrawal - Peace proposals without a sworn covenant may mean a plot is underway - Soldiers leaning on their weapons may mean they are hungry - Those who draw water and drink first before carrying it back may mean they are thirsty - Men seen whispering together in small groups may mean discontent in the ranks

The principle: every behaviour is a signal. Most people ignore what they can see because they're listening to what they're told.

The chapter closes with a lesson on discipline that cuts against purely authoritarian leadership: 'If soldiers are punished before they have grown attached to you, they will not prove submissive.' You cannot demand obedience from people who don't yet trust you. Relationship comes first , then authority. But once trust is established, inconsistent discipline breeds contempt. The general who is too soft after winning loyalty is just as dangerous as the one who punishes before earning it.