Although the other contributors to military capability assessed in this study are important, quality and quantity of weaponry cannot be ignored. In 2013, for example, the U.S. Defense Department spent 31 percent of its budget developing and acquiring new weapon systems. Even if one regarded this proportion as excessive, few would argue that developing and acquiring new weapon systems was completely unjustified.

The challenge is to develop a methodology for assessing the quality of a military's weaponry in aggregate. One approach would be to simply total the numbers of each type of major weapon system a military possesses. The disadvantage of such an approach would be that it would not account for qualitative differences between different of weapon systems. Using this system, a 1950s-era main battle tank would be regarded as equivalent to late-twentieth-century main battle tank.

During the Cold War, the U.S. Army developed a system called Weapon Effectiveness Index/Weighted Unit Value (WEI/WUV). This system calculated an overall Weapon Effectiveness Index (WEI) for each weapon based on its technical characteristics (rate of fire, maximum effective range, thickness of its armor, road speed, ground pressure, etc.). For each unit, an aggregate value, called the Weighted Unit Value (WUV), could then be calculated by multiplying the WEIs of each type of weapon the unit possessed by the number of that type of weapon the unit possessed and computing a sum weighted according to the category of each weapon (small arms, tanks, antitank missiles, artillery, armed helicopters, etc.). This approach had several drawbacks, including the apparent subjectivity involved in assigning the weights for different technical characteristics of a weapon system as well as to different categories of weapons, and the fact that it only applied to ground forces, not air forces or naval forces. In any case the U.S. government does not appear to have released WEI/WUV scores since 1979, before many of the weapon systems in use in the PLA in 2000 and later entered service.

The approach taken in this chapter falls between simply counting numbers of each type of major weapon system and the WEI/WUV system in its complexity. Each major category of weapon (e.g., main battle tanks) is subdivided into a small number of subcategories that can be regarded as qualitatively different from each other.