用兵有言，吾不敢為主；而為客。不敢進寸；而退尺。是謂行無行；攘無臂；扔無敵；執無兵。
1. A master of the art of war has said, 'I do not dare to be the host (to commence the war); I prefer to be the guest (to act on the defensive). I do not dare to advance an inch; I prefer to retire a foot.' This is called marshalling the ranks where there are no ranks; baring the arms (to fight) where there are no arms to bare; grasping the weapon where there is no weapon to grasp; advancing against the enemy where there is no enemy.
禍莫大於輕敵。輕敵幾喪吾寶。故抗兵相加，哀者勝矣。
2. There is no calamity greater than lightly engaging in war. To do that is near losing (the gentleness) which is so precious. Thus it is that when opposing weapons are (actually) crossed, he who deplores (the situation) conquers.
Legge's Comments
玄用, 'The Use of the Mysterious (Dào).' Such seems to be the meaning of the title. The chapter teaches that, if war were carried on, or rather avoided, according to the Dào, the result would be success. Lǎozǐ's own statements appear as so many paradoxes. They are examples of the procedure of the Dào by 'contraries,' or opposites.
We do not know who the master of the military art referred to was. Perhaps the author only adopted the style of quotation to express his own sentiments.