A U.S. fighter jet flies over northern Iraq after conducting airstrikes in Syria against Islamic State group targets in Syria. (Senior Airman Matthew Bruch/Associated Press)

Rachel E. VanLandingham, a retired Air Force lieutenant colonel and judge advocate, is an associate law professor at Southwestern Law School and vice president of the National Institute of Military Justice. Geoffrey S. Corn, a retired Army lieutenant colonel and formerly the Army’s top law of war adviser, is a professor at Houston College of Law.

During the Vietnam War, U.S. military leaders infamously used the number of enemy killed — body counts — as the measure of U.S. battlefield accomplishment. Even if accurate, these numbers were a spectacular failure as a touchstone of success.

It was ironic that Vietnam War opponents used a similar but opposite body count to undermine the war effort — that of civilians killed. The iconic image of protesters chanting, “Hey, hey, LBJ, how many babies did you kill today?” foreshadowed a paradigm shift in how the U.S. military approaches the issue of civilian casualties, particularly in asymmetric conflicts. Now, “civilian protection” is, appropriately, central to both the international law of war and the legitimacy of U.S. military operations. From the highest levels of strategic command to the dirt and mud of tactical execution, U.S. forces are subject to an ever-increasing imperative to mitigate risk to innocent civilians caught in the crossfire of today’s battlefields.

In our current fight against the Islamic State, both types of body counts tick on. However, enemy casualty numbers seem overshadowed by interest in the Pentagon’s efforts to limit — or even completely prevent — civilian casualties. The Defense Department regularly publicizes its assessments of the historically low number of civilian casualties in this conflict. In July, the Pentagon touted the total the number of U.S.-confirmed civilian casualties: 55 civilian deaths and 29 injuries over two years (compared with more than 200 allegations). A few weeks later, U.S. Central Command emphasized the difference between allegations of civilian casualties and those CENTCOM could confirm.

This emphasis on precise, casualty-averse warfare may be distorting the public’s understanding of war and law. The public accounting of every allegation of coalition-caused civilian casualties on the Islamic State battlefield, and the outcome of every civilian casualty investigation, is conditioning both domestic and international audiences to expect that international law demands analogously low levels of civilian casualties in all wars and that this level can be met while successfully prosecuting the conflict. This is wrong. It is also dangerous.

The Islamic State is exploiting this emphasis on civilian casualty avoidance to gain both tactical and strategic success. From its documented use of civilians as human shields to the practice of hiding weapons in civilian homes and schools, the group has adopted the playbook of other illicit armed groups such as Hamas and Hezbollah.

The Pentagon should accompany its transparency initiatives with a much stronger reminder that the law of war often, even if unfortunately, permits civilian casualties when necessary to accomplish legitimate military objectives. And that it is almost always the Islamic State’s fault, not the coalition’s, when such casualties are inflicted. In an asymmetric war against an enemy that violates the law by hiding and fighting among civilians, these casualties are frequently a calculated price of attacks aimed at destroying enemy fighters and other military targets.

That is, civilian casualties often are the product of strikes conducted despite the knowledge that civilians are likely to be harmed. As long as coalition forces ensure that the law of war’s yardsticks are met — that the military advantage to be gained by a strike outweighs the potential harm to civilians, and that reasonable care has been taken in choice of weapons and tactics to minimize the effect on civilians — civilians may, and unfortunately will often be, killed and injured. That is the horrible essence of modern, lawful war, and a burden that our young warriors carry into battle. But the responsibility for the vast majority of this suffering lies at the feet of the illicit enemy.

Confusion regarding the law of war only incentivizes the Islamic State and similar groups to continue their illegal methods of fighting among civilians. In this vein, if the Pentagon continues to over-emphasize the rarity of civilian casualties during coalition airstrikes, it risks sending potentially delegitimizing shockwaves once airstrikes are used in close air support of ground forces retaking cities and villages, in which the Islamic State’s use of human shields and other illegal tactics will almost inevitably result in much higher civilian casualty numbers.

Just as in the Vietnam-era, body counts are a false indicator of battlefield success. The United States and its partners need to emphasize their effort to reduce civilian risk, not simply the numerical outcome of that effort. This is why: Enemies such as the Islamic State get a “vote” in that outcome, and can frustrate the best efforts to prevent civilian suffering. What we should always highlight, therefore, is that it is the Islamic State that ultimately bears responsibility for the tragic battlefield harm that befalls civilians today.