Selecting a unit to carry out a particular mission is currently a highly manual process that typically involves assessing and then comparing the perceived strength of friendly and enemy forces. A unit is then chosen based on whether it meets or exceeds specified force-strength requirements. For example, to carry out a deterrent mission, sound military practice suggests that the ratio of friendly to enemy force strength be greater than or equal to two. For attack missions, the ratio should be greater than or equal to three. A unit's strength is based on the combined assessments of different characteristics that include:
Friendly as well as enemy unit forces have an associated ``base-strength" value which, in some sense, represents the power of a unit given no deficiencies with respect to its characteristics. If a unit has its full complement of troops, armament, equipment, and so forth, then the unit can be said to be at its designed level of strength (i.e., power). Intuitively, deficiencies in one or more characteristics should be reflected in terms of a reduction in a unit's overall power. Expressing deficiencies is traditionally done in terms of a ``force multiplier" (FM) that is associated with each characteristic.
The overall power of a unit should decrease as a unit becomes increasingly deficient in one or more characteristics. One commonly used method involves multiplying the FMs and the unit's base-strength value. The ration of the power of friendly force units to the power of enemy force units should meet or exceed the mission force-strength ratio requirements. For the case where multiple units meet or exceed such requirements, choosing any of these alternatives is said to be equally valid. If units far exceed a force-strength ratio requirement, it may be wasteful to select such a unit if alternative units are available which meet or exceed the requirements.