The friendship of Guan and Bao
In his youth Guan Zhong went into trade with Bao Shuya, and always took the larger share of the profit — Bao Shuya said it was because his household was poor, not because he was greedy. Guan Zhong had once served Prince Jiu against Duke Huan, and even shot Huan through the belt-hook with an arrow. When Huan took the throne and wanted to kill him, Bao Shuya urged strongly: "If you would be hegemon, none but Guan Yiwu will do." Huan set aside the grudge of that arrow and made him chancellor. In old age Guan Zhong sighed, "My parents gave me birth; Bao knew me."
The stratagem against Hengshan
When Qi wished to attack the state of Hengshan, Guan Zhong sent not a single soldier: first he bought up, at high prices, the weapons that were Hengshan’s specialty; other states followed suit, and all Hengshan abandoned farming to forge arms; then Qi bought grain at high prices, driving up its price everywhere. When the moment came, Qi stopped buying and sealed the passes — Hengshan, without grain or preparation, surrendered without a fight. This is one of the earliest cases of economic warfare in the histories, and it still looks familiar more than two thousand years later.