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.

Emerging outside, he crawled up on a wall to examine the “splash” mark the RPG had made on the house. The experienced operator could tell the rocket had been dipping by the time it impacted, meaning it had been fired from some distance away. Hollenbaugh mentally traced the angle of fire as far as he could see, then raced back upstairs to get a longer view. Spotting a small dark hole in some rubble about 300 meters away, he figured that was the RPG gunner’s position. He fired several M4 rounds into the hole and told the Marine forward observer to mark it as a potential mortar target.

For the next hour or so, insurgents probed the U.S. positions and traded occasional shots with the Americans. The Delta sniper team leader, J.N., decided to pull his men back to the other sniper’s position, from where they could better utilize their rifles’ range. After speaking with Hollenbaugh, E Company commander  Captain  Doug Zembiec  sent  two Marines  to the  roof to replace  the  snipers.  Between himself, Boivin, Briggs, and the two Marines, Hollenbaugh calculated there were enough men on the roof to cover all sectors of fire, especially considering the presence of the Marines in the northern house and the Delta snipers to the rear.

Within a couple of minutes of the two Marines arriving on the roof, the volume of insurgent fire suddenly increased as word of the Americans’ location spread. More than 300 militants arrived by the truckload to join the fight. Thousands of bullets and scores of RPGs tore into the walls of both houses. The insurgents “really believed this was the full- on invasion of Fallujah,” recalled Hollenbaugh. “They were just throw- ing everything  they  had at  us.” Using alleyways  and  positions  in neighboring houses, insurgents got close enough to hurl grenades onto the northern rooftop, wounding several Marines. Hearing their screams, Briggs left his position and, together with the forward observer, sprinted across the no-man’s-land between the two buildings to help treat and evacuate the wounded, exposing himself to enemy fire at least six times. The situation was now perilous for the Americans, outnumbered ten to one by insurgents who were moving along the walls of the two build- ings in an effort to surround them. Shouting to be heard above the din, the U.S. troops rained fire and threw grenades down on their attackers. On the southern roof Hollenbaugh, Boivin, and the two Marines were fighting hard to hold off the insurgents—a tough job for only four men. Then a grenade landed on the roof and exploded, grievously wounding both Marines, one of whom stood up. “He’s got his hands on his face and blood’s coming through his fingers, it’s just ugly,” Hollenbaugh recalled. Concerned that the Marine was exposing himself to insurgent fire, the Delta master sergeant hustled him into the crowded stairwell, before returning to the other  wounded Marine,  an NCO whose name he never learned. Lying facedown, the Marine pointed with his right hand in the direction of where he thought the more junior Marine was still lying. “Take him first, take him first,” he told Hollenbaugh, who was impressed  with the  Marine’s  selfless  bravery. “This guy’s crawling backwards and he’s just leaving a streak of blood, so you know he’s hurt really bad,” he said later. “I already got him,” the operator told the Marine, as he grabbed his belt, yanked him to his feet, and moved him to the stairwell.

With Boivin still covering his sector, Hollenbaugh moved between his own fighting position and those left vacant by the Marines’ departure, firing his M4 and tossing grenades. Another incoming grenade exploded on the roof, with shrapnel catching Boivin behind the ear and in the back of his arm. “Don, I’m hit,” he yelled. Sitting by the stairwell opening, which was surrounded on three sides by walls, Hollenbaugh worked to patch Boivin up quickly. Reaching into a “go bag” that the Delta guys had brought, which contained grenades, spare magazines, a signal kit, and medical supplies, he grabbed Kerlix gauze bandages and green do-rags. He packed the Kerlix into the head wound, tied it off with do-rags, and told Boivin to turn and face him. “You look really cool,” he teased the  heavy breacher.  Despite  the  nasty wound, Boivin—later described by Hollenbaugh as “a tough, tough individual”—was about to return to the fight when both men noticed what looked like a mouse moving under  a clumped-up blanket the Marines had been using to shield themselves from the sun. Realization came to each soldier simultaneously. Staring at each other in wide-eyed alarm, they yelled the same word: “Grenade!”

Excerpt from Sean Naylor’s relentless strike.