前禦與邊備
Forward Defense and Border Security
諸去大軍為前御之備者,邊縣列候,相去三、五里。聞大軍為前御之備,戰則皆禁行,所以安內也。
All units that leave the main army to serve as forward defensive positions shall be stationed along the border counties as observation posts, spaced three to five li apart. When it is known that the main army is establishing forward defenses, all civilian movement is prohibited during the campaign. This is the means of securing the interior.
Notes
列候 (lie hou, 'observation posts') were the Warring States equivalent of early warning stations, positioned along the frontier at intervals of 3-5 li (approximately 1.2-2 km). This spacing ensured visual and signal contact between posts. The automatic civilian lockdown upon mobilization connects back to the 分塞 (sector control) doctrine of Chapter 15.
