It appears that discussion of the meaning of lethality, as related to the use of the term in the 2018 U.S. National Defense Strategy document, has sparked up again. It was kicked off by an interesting piece by Olivia Gerard in The Strategy Bridge last autumn, “Lethality: An Inquiry.”
Gerard credited Trevor Dupuy and his colleagues at the Historical Evaluation Research Organization (HERO) with codifying “the military appropriation of the concept” of lethality, which was defined as: “the inherent capability of a given weapon to kill personnel or make materiel ineffective in a given period, where capability includes the factors of weapon range, rate of fire, accuracy, radius of effects, and battlefield mobility.”
It is gratifying for Gerard to attribute this to Dupuy and HERO, but some clarification is needed. The definition she quoted was, in fact, one provided to HERO for the purposes of a study sponsored by the Advanced Tactics Project (AVTAC) of the U.S. Army Combat Developments Command. The 1964 study report, Historical Trends Related to Weapon Lethality, provided the starting point for Dupuy’s subsequent theorizing about combat.
In his own works, Dupuy used a simpler definition of lethality:
- “…lethality, or destructive power, of weapons…” [Numbers, Predictions and War: Using History to Evaluate Combat Factors and Predict the Outcome of Battles (Indianapolis; New York: The Bobbs-Merrill Co., 1979), p. 6]
- “Lethality—the ability to injure and if possible to kill people.” [The Evolution of Weapons and Warfare (Indianapolis, IN: The Bobbs-Merrill Company, Inc., 1980), p. 286]
- “All weapons have at least one common characteristic: lethality. This is the ability to injure and, if possible, to kill people.” [Attrition: Forecasting Battle Casualties and Equipment Losses in Modern War (Falls Church, VA: NOVA Publications, 1995), p. 25, which was drawn from earlier HERO reports].
He also used the terms lethality and firepower interchangeably in his writings. The wording of the original 1964 AVTAC definition tracks closely with the lethality scoring methodology Dupuy and his HERO colleagues developed for the study, known as the Theoretical Lethality Index/Operational Lethality Index (TLI/OLI). The original purpose of this construct was to permit some measurement of lethality by which weapons could be compared to each other (TLI), and to each other through history (OLI). It worked well enough that he incorporated it into his combat models, the Quantified Judgement Model (QJM) and Tactical Numerical Deterministic Model (TNDM).