《明史·列传·卷七十一》
精锐军队全都集中到西部，老弱士卒才留在北边，万一北边出现战情，而在西边的军队一下又离不开，首尾脱节，远近都被困住，这合算吗？
精锐既尽乎西，老弱乃留于北。万一北或有警，而西未可离，首尾衡决，远近坐困，其可为得计哉？
The best troops are all concentrated in the west, leaving only the old and weak soldiers in the north. If there is an emergency in the north and the troops in the west are unable to leave, it will result in a severed connection between the front and rear and both will be trapped, far and near. Will this pay off?