A leaked RAND report on the counterinsurgency effort in Afghanistan includes this little tidbit, according to the Guardian UK:
Its sources complain of commanders who have slipped into relying on “the fallacy of body counts”, discredited after the war in Vietnam as a measure of success.
…An anonymous source quoted in the report stated that “operational commanders” continued to “indulge in the fallacy of body counts, and a month in which more Taliban are killed than in the previous month” was seen as progress. He added: “This is actually more likely to reflect the fact that there are more enemy on the battlefield than there were before.”
A January 2009 TomDispatch article explained the historical significance of body counts:
It was in the context of defeat and then frustration in Korea that the counting of enemy bodies began. Once Chinese communist armies had entered that war in massive numbers in late 1950 and inflicted a terrible series of defeats on American forces but could not sweep them off the peninsula, that conflict settled into a “meatgrinder” of a stalemate in which the hope of taking significant territory faded; yet some measure of success was needed as public frustration mounted in the United States: thus began the infamous body count of enemy dead.
The body count reappeared quite early in the Vietnam War, again as a shorthand way of measuring success in a conflict in which the taking of territory was almost meaningless, the countryside a hostile place, the enemy hard to distinguish from the general population, and our own in-country allies weak and largely unable to strengthen themselves. Those tallies of dead bodies, announced daily by military spokesmen to increasingly dubious reporters in Saigon, were the public face of American “success” in the Vietnam era. Each body was to be further evidence of what General William Westmoreland called “the light at the end of the tunnel.” When those dead bodies and any sense of success began to part ways, however, when, in the terminology of the times, a “credibility gap” opened between the metrics of victory and reality, the body count morphed into a symbol of barbarism as well as of defeat. It helped stoke an antiwar movement.