Tom Vanden Brook

USA TODAY

WASHINGTON — The Pentagon tracks every Islamic State fighter it kills and reports the body count regularly to the highest levels but refuses to discuss the toll publicly, USA TODAY has learned.

A senior Defense official said last week that the total of 50,000 militants killed since the U.S.-led air war began in 2014 is likely a conservative estimate. Killing large numbers of enemy combatants affects their ability to fight and hold territory, said the official who, like other Defense officials interviewed for this story, spoke on condition of anonymity because they were not authorized to speak publicly about the body counts.

Officials at the Pentagon and Central Command, which oversees combat against the group also known as ISIL, had agreed in November to release more detail on enemy killed-in-action figures and how they are tabulated to USA TODAY. But those officials backed out of the agreement. The numbers are not classified, but military officials now refuse to talk about them, or to explain why. By contrast, the British military releases estimates not only of enemy killed but also those wounded and the type of weapon used.

Commanders and officials at Central Command and at the Pentagon have received regular, sometimes weekly, updates of the number of ISIL fighters killed in U.S.-led attacks, a senior officer said.

The Pentagon's refusal stems from its longstanding credo, echoed by top commanders like retired general David Petraeus that it’s impossible “to kill or capture our way out” counterinsurgencies like those in Iraq and Afghanistan. Their reticence also has roots in Vietnam when daily news briefings in Saigon, derided as the “5 O’Clock Follies,” boasted body counts to show the war was being won, according to a second senior official familiar with the reports and military analysts.

“People see such numbers as harkening back to Vietnam when we misdiagnosed progress based on body counts," said Michael O’Hanlon, a military analyst at the Brookings Institution. The counts "effectively turned field commanders into leaders incentivized to kill more in order to prove their merits,”

Another reason for the reticence: the killing only keeps pace with Islamic State recruiting. Despite 50,000 or more Islamic State fighters, the militants continue to field a force between 20,000 and 30,000, said the senior officer.

Scott Murray, a retired Air Force colonel and intelligence expert who helped lead efforts to develop ISIL targets in the first part of the war, said counting the dead has been largely discredited as a tool to evaluate progress in war.

"It's that simple," Murray said. "Body counts are part of the narrative of how to lose a war."

But privately — and on rare occasion in public — senior battlefield commanders admit that killing and counting Islamic State dead matters.

A lot, as it turns out.

Army Lt. Gen. Sean MacFarland, who led the allied war effort until this summer, tracked the number of enemy killed as one measure of progress. He told reporters at his last briefing in August that 25,000 ISIL fighters had been killed in the previous 11 months, an increase in the pace of lethal attacks.

“The numbers are a best estimate — not exact, although the team tries hard to get it right,” MacFarland said in an email. “The best proof of their basic accuracy is the increasing momentum of the campaign. The enemy is unable to put fighters in the field in the same quantity and quality of a year ago.”

How they’re counted

The Pentagon has deployed a dizzying array of spy planes and other technology to the Middle East to track enemy combatants, develop plans to attack targets and to assess what’s been blown up and who has been killed.

Reaper and Predator drones loiter relentlessly in the skies over Iraq and Syria, providing video footage for commanders. Imagery also streams in from other warplanes tracking their bombs, missiles and rounds of ammunition from their cannons.

Central Command and the Pentagon are quick to claim credit — down to the individual item — for ISIL equipment and materiel destroyed in airstrikes. For instance, a news release Friday boasted of blowing up 168 oil tankers on Dec. 8 near Palmyra, Syria. The attack deprived ISIL of $2 million in revenue, the military said.

Yet neither Central Command nor the military headquarters in Iraq responded to a query about whether truck drivers are considered fighters, and if any were killed in the airstrikes.

Pentagon acknowledges riskier airstrikes, more civilian casualties

Virtually every attack against ISIL is documented by video cameras or infra-red devices that can peer through smoke or clouds, the second official said. A missile that hits a motorcycle carrying two militants is scored as two enemy dead, the officer said. Infra-red devices can also detect the heat from dead bodies even hours after an attack.

The British military is more forthcoming about the human toll of its attacks. It estimates that British warplanes have killed our wounded 1,915 ISIL fighters from Sept. 2014 to Nov. 2016, according to Ministry of Defence figures. Each attack, the type of weapon used and the number of killed and wounded has been made public. A Hellfire missile attack on May 1 of this year, for example, killed eight and wounded three ISIL militants.

The significance of body counts

Commanders look at several measures to gauge progress against ISIL. Across the map of Iraq and Syria, allied ground forces, assisted by U.S. commandos and advisers, have driven ISIL fighters from huge blocs of territory and are cornering them in the holdout cities of Mosul in Iraq and Raqqa in Syria. Defense Secretary Ash Carter told allies in Bahrain on Saturday that targeted attacks have decimated ISIL's leadership.

Destruction of oil wells, another source of revenue, or banks that finance ISIL operations, is another benchmark.

But the volume of enemy dead is still seen as a key metric, the second official said. Top commanders in the field and in Washington are briefed, often daily, on the results of attacks by U.S. and allied warplanes on Islamic State targets and how many fighters perished in them.

At first glance, the arithmetic doesn’t add up to success, the second official said. Despite killing 50,000, ISIL appears to replace fighters as quickly as it loses them. It has done so by aggressive recruiting that seems likely to continue.

New rules allow more civilian casualties in air war against ISIL

Would you rather have 80,000 ISIL fighters? this source asked. Or 30,000? Killing 50,000 has made a marked difference in their ability to fight and made recruits aware of the cost of joining, the second official said.

The military is left in a quandary when it comes to discussing the figures, O’Hanlon said. Damned if they discuss them, damned if they don't.

“A reduction in body counts suggests the war isn’t going so well,” He said. “An increase means either there are more enemy than you thought or you are killing more innocents than you were before. It’s just, from military leadership’s point of view, a no-win proposition, especially in insurgencies where the supply of potential new recruits is often nearly limitless — so more attrition to the enemy, even if genuine, may not mean net progress in the campaign.”