《孙子兵法·九地篇》
根据不同地区采取不同的行动方针，要及时应变，能屈能伸，进退得宜，掌握士卒在不同情况下的心理状态。这些，都是将帅不能不认真考察和仔细研究的。
九地之变，屈伸之利，人情之理，不可不察。
<5>. Take different courses of action according to different regions, respond timely, be able to bend and stretch, advance and retreat properly, and grasp the psychological state of soldiers in different situations. These are all things that generals cannot but seriously consider and study.