This week, a Pentagon official anonymously told USA Today that the U.S.-led air campaign against ISIS had killed 20,000 of the group’s fighters in just over a year. That figure was up from July, when “military and intelligence estimates” suggested that 15,000 members of the Islamic State had been killed…

Somehow, though, ISIS’s “overall force” is the same size as it was when the U.S. air campaign expanded into Syria over a year ago, per the same official who gave USA Today the updated casualty figures this week. ISIS is famously adept at recruiting foreign fighters, but Long War Journal’s Thomas Joscelyn was skeptical that recruitment could account for those numbers…

One reason to tally the number of enemy fighters killed is to know what the U.S. military and its allies are up against. Early on in the Iraq War, the U.S. military maintained that it wasn’t keeping track at all—“American officers have learned,” The Times reported at the time, “that no figures are vastly better than bad figures.” But the practice started creeping back in Iraq 10 years ago, in what The Washington Post called “an ad hoc process … with authority to issue death tolls pushed out to the field and down to the level of division staffs,” usually after major operations.