形 is a very comprehensive and somewhat vague term. Literally,
“form,” “body,” it comes to mean “appearance,” “attitude” or
“disposition;” and here it is best taken as something between, or
perhaps combining, “tactics” and “disposition of troops.” Ts‘ao
Kung explains it as 軍之形也，我動彼應兩敵相察情也 “marching and
counter-marching on the part of the two armies with a view to
discovering each other’s condition.” Tu Mu says: “It is through
the 形 dispositions of an army that its condition may be
discovered. Conceal your dispositions (無形), and your condition
will remain secret, which leads to victory; show your
dispositions, and your condition will become patent, which leads
to defeat.” Wang Hsi remarks that the good general can
變化其形因敵以制勝 “secure success by modifying his tactics to meet
those of the enemy.” In the modern text, the title of the chapter
appears as 軍形, which Capt. Calthrop incorrectly translates “the
order of battle.”