It was still dark when Master Sergeant Don Hollenbaugh heard the call to prayer echoing from a minaret 300 meters to the north. The haunting sound unsettled the Delta operator. “This is not going to be a good day,” he told Staff Sergeant Dan Briggs, a twenty-eight-year-old Delta medic kneeling beside him on a street corner in northwest Fallujah. “This could get ugly quick.”

At 4 a.m. that morning, six Delta soldiers and roughly forty Marines from E Company, 2nd Battalion, 1st Marine Regiment had quietly advanced on foot about 300 meters in front of Coalition lines. The Delta contingent included Hollenbaugh and Sergeant Major Larry Boivin, Combat Support Troop’s operations sergeant and senior heavy breacher respectively; three A Squadron snipers; and Briggs. A fourth sniper occupied a building to the rear, from which he could overwatch the patrol’s route and warn of any movement ahead. Hollenbaugh and Boivin were there at the Marines’ request to provide added firepower of a specific type: thermobaric AT4 rockets. The AT4 was ubiquitous in U.S. Army and Marine Corps infantry formations, but Delta’s thermobaric rounds were not and were thus the envy of the Marines. Shoulder-fired from disposable launchers like all AT4s, they worked by rapidly driving up heat and pressure in any confined space into which they were fired. Used properly, they were enormously destructive. The Delta soldiers had already trained the Marines on the weapon and supplied them with rounds, but the Marines still didn’t feel comfortable employing the thermobarics, so had asked Hollenbaugh and Boivin to accompany the patrol into Fallujah to fire the rounds themselves. “They didn’t feel like the training was sufficient,” Hollenbaugh said. “And given the lethality of those weapons, I think that was a good call.”

After holding static positions on the city’s edge for several days, the U.S. troops were worried that the insurgents had figured out their “blind spots”—locations from which the militants could launch attacks unseen from Coalition lines. The early morning patrol was an effort to “mix up the battlefield . . . so that the snipers could change their lanes and if need be, we could put these thermobaric weapons to use,” Hollenbaugh recalled. As he knelt and whispered to Briggs, the Marines were clearing and occupying a pair of houses north and south of an intersection. The Delta soldiers entered the southern one and took positions on the flat rooftop, which measured about ten meters by fifteen meters. The Marines did the same on the northern rooftop and on the houses’ other floors. Low walls surrounded both rooftops. Using sledgehammers, the Americans spent the hour before dawn knocking holes in them to create fighting positions. The Marines were expecting a fight. They would not be disappointed.

At first light, a rocket-propelled grenade exploded against the southern house, followed a few minutes later by a burst of machine gun fire. As Hollenbaugh peered out of his fighting position another RPG hit a few feet below, close enough that he felt the heat and the spray of grit on his face. “Luckily, I had one earplug in and eye protection on,” he recalled. He quickly put the second earplug in. “Hey, keep watch over my sector, I’m going downstairs to see where this thing came from,” Hollenbaugh told Boivin.