Book 13 Chapter III Paragraph 5

When the enemy is desirous of taking possession of the territory of the conqueror's friend, then the conqueror may, under the pretence of compliance, supply the enemy with army. Then having entered into a secret concert with the friend, the conqueror may pretend to be under troubles and allow himself to be attacked by the enemy combined with the neglected friend. Then, hemmed from two sides, the enemy may be killed or captured alive to distribute his territory among the conqueror and his friend.