From 《
史记·
孙子吴起列传》 (Records of the Grand Historian). The general Tian Ji of Qi was losing horse races to the king. Strategist Sun Bin advised: race your worst horse against his best (lose), your best against his middle (win), your middle against his worst (win). Net result: 2-1 victory. Now used for any 'allocate your strong assets where they win' tactic.