Five months and 1,800-plus strikes into the U.S. air campaign against ISIS, and not a single civilian has been killed, officially. But Pentagon officials concede that they really have no way of telling for sure who has died in their attacks‚—and admit that no one will ever know how many have been slain.

“It’s impossible for us to know definitively if civilians are killed in a strike. We do everything we can to investigate. We don’t do strikes if we think civilians could be there. But we can’t have a perfect picture on what’s going on,” one Pentagon official explained to The Daily Beast.

Stuart Jones, the U.S. ambassador to Iraq, told al Arabiya that U.S. and coalition strikes in Iraq and Syria have killed 6,000 ISIS fighters. That no civilians could be among that figure strikes observers and even military officials as all but impossible.

Yet neither the Iraqi and Syrian governments nor the Congress are pushing U.S. military for answers. And with no American ground troops to assess the damage of the air campaign, human rights groups and Pentagon officials alike admit that one casualty of the war itself is an accurate breakdown of who has been killed in it.

“If you don’t know the very basic information, for example who is dropping bombs and where, it is very hard to verify or deny claims of civilian harm,” said Marla Keenan, managing director at Center for Civilians in Conflict (CIVIC), which tracks civilian casualties.

Civilian deaths, a keystone metric of the U.S. campaign to win hearts and minds in Iraq during the 2003-11 war, has now become the statistic no one wants to talk about. The U.S. military said earlier this month that it’s investigating claims of slain innocents. But until recently, the attitude towards so-called “collateral damage” seemed remarkably incurious, despite the Pentagon’s assertions that their strikes are so precise that they minimize civilian deaths and that they are committed to investigating suspected civilian deaths.

“I am tracking no civilian casualties,” Lt. Gen. James L. Terry, commander of Operation Inherent Resolve, the U.S. campaign in Iraq and Syria, told reporters at a Pentagon briefing last month. “Where we—if we even suspect civilian casualties, we would immediately direct investigation, determine the cause, and then seek to understand the lessons learned from that and apply those lessons learned.”.

U.S. Central Command, which oversees military missions in the region, is not transparent about how they conduct investigations, however. CENTCOM officials have said they are investigating two claims of civilian deaths both which occurred in late December—after Terry asserted there were no such deaths. But they have not said where those deaths may have occurred other than say one happened in Iraq and Syria, who raised concerns, precisely how many civilians may have been killed or how CENTCOM is conducting its investigation. So far, CENTCOM officials said, they usually open such cases when their own evaluation, human rights groups or media outlets make claims of civilian deaths. In all, the two cases involve less than five civilians, CENTCOM officials said.

One reason CENTCOM can be so vague is that no one in a position of authority is asking aggressive questions about civilian casualties. In testimony on Capitol Hill about the U.S. campaign against the Islamic State, no one has pushed Secretary of Defense Chuck Hagel, Army Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff, or Brett McGurk, President Obama’s deputy envoy for the coalition effort to defeat Islamic State, on the issue of civilian casualties.

“I think the public just prefers to believe we can drop bombs and not harm anyone,” Keenan said.

In both Iraq and Syria, the governments themselves are believed to have killed more civilians than the U.S. strikes, making it unlikely they’d raise concerns about civilian deaths. In Iraq, the Iraqi security forces and local militias have been responsible for hundreds of deaths this year alone, according to Iraq Body Count, which has been tracking civilian casualties since the 2003 U.S. invasion. And in Syria, the regime of President Bashar al Assad is suspected behind the deaths of tens of thousands of civilians since the war began there in 2011.

More recently Assad has piggybacked on U.S. air strikes to wage his own war against his opponents and has then blamed civilian deaths on coalition forces.

And as of now, both Iraq and Syria are benefiting from the strikes, which is perhaps why the Iraqi government has not pressed the issue with the United States, U.S. officials told The Daily Beast. They want the U.S. campaign to continue, officials explained.

“I don’t see the upside for the Iraqi government. The Iraqi government wants as many sorties as the coalition will fly and as many weapons as the coalition will give them. Civilian casualties are a source of friction,” Christopher Harmer, an analyst for the Institute for the Study of War, a Washington, D.C.-based research group.

The Syrian government also wants the campaign to continue as it is benefiting from the war on ISIS, which threatens the current regime. And in all their propaganda videos, ISIS rarely brings up civilian deaths at the hands of U.S. and coalition forces. Perhaps that has something to do with all of the civilians ISIS fighters have killed themselves.

Coalition and U.S. strikes are usually carried out in small towns and villages where the number of residents is smaller and independent observers are even less. Allegations come from residents who can make contact with human rights groups or journalists, a far departure from the last Iraq war when U.S. troops and journalists blanketed the country. Those who claim such deaths can have an either political or financial incentive for doing so.

The lack of credible information leads to various sides making their own claims, and a war that is having unknown effects. For example, on Dec. 28, coalition forces struck the Syrian city of al Bab, which has been the scene for strikes by both coalition and Syrian government forces targeting rebel forces and ISIS. Residents told McClatchy that coalition strikes killed 50 residents in a nearby jail. Pentagon officials said its forces never struck the jail and pinned the deaths—which, based on local reports, they believe is closer to 25 -- on Assad forces during a strike launched two days prior. No one can say for certain which claim is true, three weeks after the initial charges were made.

That such attacks could be happening against civilians by government forces without repercussions is a failure of the nations that back them, observers said.

“The international community supporting these governments has a responsibility to put pressure on these governments to protect their civilians,” said Sahr Muhammed, senior program manager for CIVIC with a focus on Middle East.

International observers do keep some rough estimates about the total number of people killed and displaced in Iraq and Syria. According to the United Nations Assistance Mission for Iraq, about 18,680 Iraqis have been slain since November 2012. (I added the numbers on the right side of the chart). In April 2014, the Syrian Observatory for Human Rights, a U.K.-based group, said it had documented the death of 150,000 Syrians since the war there erupted in March 2011.

But there’s maddeningly little information on how many of those deaths have come at the hands of the U.S.-led coalition. The only group that appears to have any breakdown of civilian deaths by coalition strikes in both countries is the International Committee of the Red Cross, which has sources and observers, but they do not release such statistics. The Syrian Observatory for Human Rights, an opposition group, occasionally reports incidents but does not appear to have a total number. Iraq Body Count counts 118 civilian deaths by coalition air strikes.

Either way, Muhammed explained, “we will never know the number of how many have been killed.”