According to Trevor Dupuy, “Suppression is perhaps the most obvious and most extensive manifestation of the impact of fear on the battlefield.” As he detailed in Understanding War: History and Theory of Combat (1987),
There is probably no obscurity of combat requiring clarification and understanding more urgently than that of suppression… Suppression usually is defined as the effect of fire (primarily artillery fire) upon the behavior of hostile personnel, reducing, limiting, or inhibiting their performance of combat duties. Suppression lasts as long as the fires continue and for some brief, indeterminate period thereafter. Suppression is the most important effect of artillery fire, contributing directly to the ability of the supported maneuver units to accomplish their missions while preventing the enemy units from accomplishing theirs. (p. 251)
Official US Army field artillery doctrine makes a distinction between “suppression” and “neutralization.” Suppression is defined to be instantaneous and fleeting; neutralization, while also temporary, is relatively longer-lasting. Neutralization, the doctrine says, results when suppressive effects are so severe and long-lasting that a target is put out of action for a period of time after the suppressive fire is halted. Neutralization combines the psychological effects of suppressive gunfire with a certain amount of damage. The general concept of neutralization, as distinct from the more fleeting suppression, is a reasonable one. (p. 252)
Despite widespread acknowledgement of the existence of suppression and neutralization, the lack of interest in analyzing its effects was a source of professional frustration for Dupuy. As he commented in 1989,
The British did some interesting but inconclusive work on suppression in their battlefield operations research in World War II. In the United States I am aware of considerable talk about suppression, but very little accomplishment, over the past 20 years. In the light of the significance of suppression, our failure to come to grips with the issue is really quite disgraceful.
This lack of interest is curious, given that suppression and neutralization remain embedded in U.S. Army combat doctrine to this day. The current Army definitions are:
Suppression – In the context of the computed effects of field artillery fires, renders a target ineffective for a short period of time producing at least 3-percent casualties or materiel damage. [Army Doctrine Reference Publication (ADRP) 1-02, Terms and Military Symbols, December 2015, p. 1-87]
Neutralization – In the context of the computed effects of field artillery fires renders a target ineffective for a short period of time, producing 10-percent casualties or materiel damage. [ADRP 1-02, p. 1-65]
A particular source for Dupuy’s irritation was the fact that these definitions were likely empirically wrong. As he argued in Understanding War,
This is almost certainly the wrong way to approach quantification of neutralization. Not only is there no historical evidence that 10% casualties are enough to achieve this effect, there is no evidence that any level of losses is required to achieve the psycho-physiological effects of suppression or neutralization. Furthermore, the time period in which casualties are incurred is probably more important than any arbitrary percentage of loss, and the replacement of casualties and repair of damage are probably irrelevant. (p. 252)
Thirty years after Dupuy pointed this problem out, the construct remains enshrined in U.S. doctrine, unquestioned and unsubstantiated. Dupuy himself was convinced that suppression probably had little, if anything, to do with personnel loss rates.
I believe now that suppression is related to and probably a component of disruption caused by combat processes other than surprise, such as a communications failure. Further research may reveal, however, that suppression is a very distinct form of disruption that can be measured or estimated quite independently of disruption caused by any other phenomenon. (Understanding War, p. 251)
He had developed a hypothesis for measuring the effects of suppression, but was unable to interest anyone in the U.S. government or military in sponsoring a study on it. Suppression as a combat phenomenon remains only vaguely understood.