Economy of force is one of the nine Principles of War, based upon Carl von Clausewitz's approach to warfare.
It is the judicious employment and distribution of forces towards the primary objective of any person's conflict.
The allocation of available combat power to such tasks, like limited attacks, defense, delays, deception or even retrograde operations is measured, in order to achieve mass at decisive points elsewhere on the battlefield.
The current doctrinal manual for army operations is FM 3–0 Operations, which defines, and describes, economy of force as follows: "Allocate minimum essential combat power to secondary efforts.
It requires accepting prudent risk in selected areas to achieve superiority—overwhelming effects—in the decisive operation.