Combat is too complex to be described in a single, simple aphorism.
From Understanding War (1987):
This is amply demonstrated by the preceding [verities]. All writers on military affairs (including this one) need periodically to remind themselves of this. In military analysis it is often necessary to focus on some particular aspect of combat. However, the results of such closely focused analyses must the be evaluated in the context of the brutal, multifarious, overlapping realities of war.
Trevor Dupuy was sometimes accused of attempting to reduce war to a mathematical equation. A casual reading of his writings might give that impression, but anyone who honestly engages with his ideas quickly finds this to be an erroneous conclusion. Yet, Dupuy believed the temptation to simplify and abstract combat and warfare to be common enough that he he embedded a warning against doing so into his basic theory on the subject. He firmly believed that human behavior comprises the most important aspect of combat, yet it is all too easy to miss the human experience of war figuring who lost or won and why, and counts of weapons, people, and casualties. As a military historian, he was keenly aware that the human stories behind the numbers—however imperfectly recorded and told—tell us more about the reality of war than mere numbers on their own ever will.