Three days before ISIS militants killed Marine Staff Sgt. Louis Cardin, the U.S. military notified his family—and the families of roughly 200 Marines—that their loved ones had moved off the USS Kearsarge, deployed to the Persian Gulf, to somewhere in northern Iraq. The letter didn’t say exactly where he had been deployed two weeks earlier, or why.

But while his family and the American public were largely being kept in the dark, members of the self-proclaimed Islamic State were acquiring detailed intelligence on the movements of Cardin, the second U.S. service member killed in Iraq, and his fellow Marines.

As it turned out, those Marines were on no ordinary deployment. Cardin and his fellow Marines were deployed near the front lines of what is expected be the biggest battle of the war, two officials told The Daily Beast, tasked to launch a mission that signaled the U.S. was again furtively expanding its mission in Iraq.

Regardless, U.S. military commanders in Iraq decided it was not safe to tell the American public.

“We made the decision a month ago to announce this on the 20th” of March, Army Col. Steven Warren, a spokesman for the U.S. effort in Iraq, told reporters Monday. “We didn’t want to make the announcement until they were fully operational. They became fully operational on Friday.”

All the while, helicopters flew overhead of a new, makeshift base delivering four artillery units and a company of soldiers, all for ISIS to see and then attack. The U.S. military believes ISIS targeted its troops, the officials said, after watching them build the base.

Cardin, of the 26th Marine Expeditionary Unit, died Saturday when an ISIS-fired rocket landed in the base he had arrived at just days earlier. Cardin, 27, of Temecula, California, was killed in his bunker; another eight troops were injured, three seriously.

The circumstances of Cardin’s death and deployment have become a familiar, disturbing pattern in this war—one where the U.S. military does not reveal what it is asking of troops until it has to, usually when a service member is killed. Up until Cardin’s death, the U.S. military said it troops were only on heavily fortified bases; that its forces were not part of any offensive operations; that they were properly secured; and that frontline troops are counted in publicly released tallies of those deployed in Iraq.

But Saturday’s attack revealed that none of that was accurate.

Cardin and his fellow Marines were at what the military called a fire base. It’s a term that harkens to the Vietnam War, referring to a temporary outpost that supports bigger bases. Rather than a large compound, a fire base is a bare-bones facility designed to support frontline troops.

The U.S. military has said that its troops were at secured bases. And yet the Marines stationed at this fire base have come under two attacks in three days. On Monday, two days after Cardin’s death, a squad of ISIS fighters stormed a compound housing the Marines. Two ISIS fighters were killed in the attack; no U.S. troops were injured.

The Marines were stationed at Makhmour, Iraq, 70 miles south of ISIS’s Iraqi capital of Mosul and the presumed launch point for any offensive. Roughly 100 U.S. advisers are working alongside 5,000 Iraqi troops stationed in the same cluster of bases. The fire base sits just 10 miles from ISIS front lines, defense officials said.

“This is the first time we’ve established a spot that is only American,” Warren said.

Moreover, Makhmour is where, in August 2015, ISIS is believed to have launched a mustard gas attack against Kurdish forces.

The U.S. military quietly acknowledged that the line between offensive and defensive warfare in Iraq blurred in Makhmour, as many expect the fire base to be part of the eventual fight to reclaim Mosul. Moreover, the defense officials said the fire base was to be the first of several, though they stopped short of specifics.

Even though they were at the front lines of the push toward Mosul, the Marines did not count in the U.S. military’s official figures of troops in Iraq. Rather they were listed as serving a temporary-duty assignment and therefore not part of the official 3,870 count of troops in Iraq. Up until Monday, the U.S. military has said fighting troops were part of their official figures.

As it turns out, the Marines are part of a second unofficial figure, troops not officially listed as part of the war. That is, the troops that are part of the most aggressive push by the U.S. military on the ground were part of a second figure—1,475 other troops that are not part of the tally, allowing the Obama administration to proclaim there are less than 4.000 troops assigned to Iraq.

When every troop is counted there are just over 5,000 U.S. troops in Iraq, according to statistics provided to The Daily Beast.

Some in the Pentagon are growing increasingly frustrated by the war of words, which some fear overshadows possible mission creep in the U.S. effort.

“Everything is about messaging,” one official explained to The Daily Beast.

Up until earlier this year, the Obama administration had said U.S. troops were not in combat, suggesting that troops stayed almost exclusively on well-guarded large bases. It was not until days after the October death of Master Sgt. Joshua Wheeler during a raid that the American public learned U.S. troops were on the front lines of raids targeting ISIS sites.

The war began as a promise of no boots on the ground. Only after the number of troops reached the thousands did the administration acknowledge that boots were on the ground.

As the Pentagon wrangled over the semantics of war, at Dover Air Force Base, Cardin’s body arrived Monday afternoon in a flagged-draped transfer case, carried by seven Marines.

Cardin, who joined the Marines Corps in 2006, died during his fifth deployment. He had previously thrice served in Afghanistan and once in Iraq.