"The Department of Defense does not routinely release detailed information regarding service members who are wounded in action. This is due to concerns about operational security and about releasing health information that may be protected," Maj, Adrian Rankine-Galloway said in a statement emailed to reporters on Monday night.
There have been exceptions. The Pentagon last month confirmed that two service members were wounded, one in Iraq and one in Syria. A pentagon official said that was done to correct inaccurate information.
"One of the things that we're concerned about here is not just operational security, but also, we do not want to provide additional information to the enemy that might enhance their own assessment of the battlefield situation and their own impact," said Pentagon Press Secretary Peter Cook.
The announcement -- which continues a policy that has been in place for several years -- comes at a time when the circumstances are changing for the hundreds of U.S. troops on the ground in Iraq and Syria.
Their stated mission is to train, advise and assist local forces in the fight against ISIS. U.S. troops are authorized to defend themselves and they can come to the aid of local forces if they come under attack. But the risk to Americans has been rising as troops are getting killed and wounded as they are taking fire and finding themselves in situations that require them to engage in combat.
Battlefield rules require U.S. troops working as advisers to stay behind what is called the "forward line of troops," known as FLOT in military parlance. But as the spokesman for the U.S.-led coalition has pointed out, the forward line can be an outdated concept.
"Since World War I, no one has really known where the front line is. It's #fluid. In the case of #Syria, we stay in #goodguycountry," spokesman Col. Steve Warren tweeted last month.
"We have to start with the distinction between combat missions and combat environments and combat situations," said Jeffrey Eggers, a former Navy SEAL and ex-National Security Council staffer.
"And clearly this is not at this stage a combat mission, but they're subject to combat conditions, and that's always been something the special operations community has been exposed to," he added. "What's new in this environment is that the advisory mission, even though it's not a combat mission -- in other words, they're not supposed to be doing the majority of the fighting themselves -- is closer to where the fighting's taking place."
While the White House continues to maintain that U.S. troops are not on a combat mission, President Barack Obama acknowledged the danger they are facing ducring his Memorial Day remarks last month at Arlington National Cemetery.
"In Iraq, in our fight against ISIL, three Americans have given their lives in combat on our behalf," Obama said, using a different acronym for ISIS.
The death of Navy SEAL Charles Keating last month underscored what's happening on the ground in Syria and Iraq.
Keating was part of team of SEALS that rushed to the rescue of other SEALS and Kurdish fighters in northern Iraq when they were attacked by more than 100 members of ISIS. He was killed in that firefight. The same SEALS had been in an earlier firefight in March, also with a group of about 100 ISIS fighters.
In both cases, the SEALs made the decision to stay and help local fighters. If the SEALs had left, those fighters would not have again trusted them, one U.S. military official said. A retreat for the SEALs was "never an option," the official said.
The firefight that killed Keating was made public because it resulted in a U.S. combat death. The first firefight in March only came to light because Keating was posthumously awarded a Silver Star for his actions in that earlier battle. The Pentagon has not disclosed whether there were any U.S. troops wounded in either of those fights.
And if there are more firefights involving large numbers of ISIS fighters and U.S. troops, it is not clear if the Pentagon will make that information public, although several weeks ago Pentagon officials did acknowledge a service member who was wounded in the region.
A decision to engage enemy forces also led to the death of Army Master Sgt. Joshua Wheeler in northern Iraq in October. Wheeler and fellow special operations troops were helping local forces rescue 70 hostages held by ISIS. When fighting broke out, Wheeler moved from his position of relative safety to help Iraqi troops. He was killed by ISIS gunfire.
Behind the scenes, senior Defense Department officials discussed whether to make more information about the wounded public but eventually decided against doing so. One of their major concerns is that information about the locations of special operations forces could emerge and put forces at risk, officials said.
The Pentagon posts aggregate data on the number of wounded on its website
. But Pentagon officials admit the information may be out of date and incomplete.
For example, as of Tuesday, the site indicates 16 personnel have been wounded in the fight against ISIS, but that does not include four other troops lightly wounded in an attack on June 9. The Pentagon has not disclosed details of that incident, but CNN learned the injuries came when a vehicle near the U.S. military advisers exploded after being hit by an anti-tank round. The statistics also do not include a U.S. soldier in Afghanistan who suffered a gunshot wound to the leg earlier this month.