One in a series of articles about three teenagers and their wartime enlistment in the Marines.

In the nine months after he graduated from high school, Lance Cpl. Daryl Crookston was trained to close and kill. The proper pursuit of the enemy was pounded into him during boot camp and combat drills.

Last month, as his unit prepared to ship out to Afghanistan, some Marines in Crookston’s platoon didn’t think he was capable of killing a man. He’s deeply religious. He had chosen to stop cursing and drinking -- and that, in the Marines’ testosterone-stoked world, suggested weakness.

Crookston, 19, and away from home for the first time, is certain he could kill if called upon, particularly if his quarry were one of the religious zealots of the Taliban. If Talibs can kill for their ideals, he said, he could kill for his.

“I’m defending my homeland -- my family -- my country,” he said, weary and filthy after a long day of training in the Mojave Desert. “And I’m willing to kill for my country.”

Combat and killing were remote concepts in June, when Crookston and two friends graduated from high school in Santa Clarita after joining the Marine Corps. They enlisted in the buddy program, which guaranteed they would go through boot camp together.

Crookston, Daniel Motamedi and Steven Dellinger hoped they would be assigned to the same unit. But after 13 weeks of boot camp and eight weeks of infantry training, they were sent to different battalions. All were in California, but training demands kept them apart.

Crookston was the first to deploy to war -- to Kandahar from the Marine base at Twentynine Palms the first week of April. Lance Cpl. Motamedi’s battalion is scheduled to leave Camp Pendleton soon on a “float,” a ship to the Middle East, where the unit could be sent to Afghanistan or Iraq by summer. Lance Cpl. Dellinger, 19, will remain at Twentynine Palms until his unit, inevitably, is deployed into combat.

For the friends, the lure of combat motivated them to enlist. They considered war a noble calling, a sure path to manhood and glory. All three chose infantry, a position virtually assured of combat. Asked whether they had second thoughts about enlisting in a time of war, all gave the same brisk answer: “No regrets.”

The friends trained together at the School of Infantry at Camp Pendleton last fall. There, the boot camp graduates were drilled on grunt work -- the dirty, demanding business of laboring in small groups to find and kill the enemy over rough terrain, sometimes in the dark. They spent days either assaulting or defending a mock Middle Eastern village erected on a bald hillside, firing blanks. During one exercise, the Marines fired wildly when attacked by a sniper, played by an instructor.

“You dumped rounds with no idea what you’re firing at!” the instructor screamed afterward. “That volley of fire probably went into civilian homes. That’s how you kill innocent people!”

Later, another instructor, Sgt. Louis Serafin, said aggressiveness was preferable to timidity. “I’d rather have them trigger-happy now, in training, than be hesitant” in combat, he said.

Serafin, an Iraq veteran, assured the Marines that it was normal to be disoriented. “Combat is controlled chaos,” he said.

The instructors stressed death and danger. The focus was on killing the enemy before the enemy could kill them. “Get yourself ready physically and mentally,” an instructor advised. “It ain’t going to be no Hollywood movie. Marines are going to die over there. Get used to it.”

Crookston and Motamedi, 18, moved on this spring to weeks of specialized desert training to prepare them for combat overseas -- Crookston at Twentynine Palms and Motamedi at Ft. Irwin, 85 miles away. At both bases, elaborate Afghan villages were stocked with wily insurgents, complacent Afghan police, inscrutable villagers and reclusive women with their faces covered -- all played by Afghan Americans.

For Crookston, boot camp and combat training were the most trying experiences of his young life. “It’s definitely not as glamorous as everyone depicted it,” he said. “It’s exhausting.”

The Marines also faced stultifying boredom, the endless rote, the mind-numbing sameness of the pale desert landscape -- all staples of overseas deployment. They slept in the dirt and cold, wolfed down packaged MREs, stank of stale sweat and unwashed feet, just like troops in Afghanistan.

Channeling the aggression

The desert training was blunt and practical. Marines learned to rub their hands together when examining a buddy for wounds in the dark; blood is sticky. They were told to carry markers for scrawling on the foreheads of the wounded: “T” after applying a tourniquet, and “M” after giving morphine.

After one live-fire exercise known as Mojave Viper, at Twentynine Palms, Capt. George Gordy critiqued Crookston’s platoon. They had not been sufficiently lethal.

“The best way to suppress someone is to freakin’ kill ‘em,” Gordy said.

He told the platoon to remember the acronym SAM-K -- suppress, assess, move and kill. The Marines nodded absently. It seemed likely that even if they forgot the first three letters, they would always remember the last. After briefing sessions, the Marines typically shout “Kill!” as a sign-off. When they are particularly motivated, they scream “Kill ‘em all!”

At Ft. Irwin one morning, Motamedi’s platoon was sent to search a village for insurgents and weapons, and to detain an HVT -- a high-value target, or insurgent leader. The platoon was accosted by the police chief and mayor, who screamed at them and tried to block their way. The Marines manhandled the police chief.

That drew a rebuke from an observer-controller known as a coyote, an Army officer acting as a sort of referee. No touching the role-players, the coyote warned.

It got worse when a villager refused a Marine’s order to move out of a doorway guarded by Motamedi. The Marine pointed his automatic rifle -- loaded with blanks -- between the villager’s eyes.

The coyote cursed and slapped the rifle barrel aside. “That’s the kind of . . . that gets civilians killed!” he screamed.

The exercise baffled some Marines. They had trained to be decisive and aggressive, but they were dressed down when they took harsh action. That was the point, the trainers said -- to learn to distinguish between insurgents and civilians, and to channel their aggression toward insurgents. They should treat civilians with respect, they were told, but within limits. “Don’t show compassion,” a gunnery sergeant said. “Compassion gets Marines killed.”

Two Marines were “killed” by insurgents and ordered to drop dead. Four more were designated as killed or badly wounded by a fake bomb that exploded with a harmless pop and hissing gray smoke. After the platoon had captured its target and loaded “casualties” for evacuation, some Marines pronounced the exercise “fake,” “bogus” and other, unprintable, adjectives.

Motamedi tried to be charitable. “It was weird, but I guess it was kind of realistic,” he said. “There are a lot of distractions. You have to multi-task and really focus.”

Just like real life

Motamedi got a good taste of reality when he and his platoon mates were rushed onto a truck headed for a live-fire exercise at Ft. Irwin one afternoon. They sat in the truck for three hours, hot and miserable. They could only listen as helicopters fired missiles, mortars rained down and other platoons assaulted targets with live ammunition. Just as in real combat, the delay was never explained.

The same week, Crookston’s platoon was sent charging into an assault on a mock Afghan village at Twentynine Palms. But except for firing a few blanks at fake insurgents high in the hills, Crookston pulled security for two uneventful hours, manning his post atop a gun truck.

Worse, instead of fighting back when the insurgents launched a counterattack, the platoon commander decided to withdraw. Crookston and his mates had to watch Taliban fighters taunt them from a ridge line.

Later, after another exercise,coyotes showed Crookston’s platoon the roadside bombs they had failed to notice on patrol.

“The scary thing was how well-concealed the IEDs were,” he said later. “One was hidden in some garbage. It makes you think about what the real thing would do to us.”

At Ft. Irwin, a civilian contractor named Jay screened a disturbing video made by insurgents. It showed a U.S. convoy in Afghanistan from the viewpoint of a mountain hide-out, where insurgents waited to detonate a roadside bomb.

On the screen, an insurgent cries out “Allahu akbar!” -- God is great. A Humvee is engulfed by a red fireball. The soldiers in the Humvee had turned off their Duke, a device that jams the radio signals that detonate three-quarters of IEDs in Afghanistan, Jay said. The device interferes with music on soldiers’ iPods.

A second insurgent-made video showed a Duke-equipped convoy passing by as an insurgent screams, “Hit them!” A confederate tries, but repeatedly fails, to trigger the IED.

Jay paused for effect, then told the Marines that not a single U.S. soldier had died in Afghanistan from a radio-controlled IED while riding in a vehicle equipped with a Duke.

“So the moral is: Keep the Duke on. It’ll save your life,” Jay said.

The focus on roadside bombs, and the drills on treating wounded buddies and avoiding civilian casualties, brought the reality of Afghanistan closer. Crookston grew more sober-minded and introspective.

He tried to convince himself that, in a way, it was better that his two friends were not going to war with him. “I don’t have to worry because I know they’re safe back at main side,” on U.S. soil, he said.

Some Marines, Crookston said, suggested telling family members that they weren’t likely to survive Afghanistan, if only to guarantee a pleasant surprise when they returned home safely.

“I don’t look at it that way,” he said. “Every time I go on a patrol, I want to think, ‘Hey, you know what, I’m coming back.’ ”

Shipping out

Crookston set about saying his goodbyes. He and Motamedi had drifted apart after infantry school. They had not talked in weeks, but they exchanged text messages saying farewell.

Crookston said goodbye in person to Dellinger, who arrived at the end of a family dinner in Valencia the night before Crookston shipped out. Crookston’s parents, Kim and Kymmer Crookston, had strung red, white and blue crepe paper above the dinner table, which bore a centerpiece with a small American flag. There were red, white and blue plates and a pie decorated with the Stars and Stripes. A handmade banner read: “Return With Honor.”

On the table was a photo of Crookston in uniform, looking resolute, and a small inscription: “Our American Hero.”

Crookston looked trim and fit. His dark hair had been shaved to the scalp, a pre-deployment ritual for first-timers. He had put off changing from T-shirt and jeans to desert camouflage fatigues, but now the time had come. He pulled on the uniform.

Late that night, Kim and Kymmer drove their son to Twentynine Palms, where buses were waiting to take his company to the flight line. They stayed up all night, waiting in the cold desert air. At 3:30 a.m., the Crookstons were among the few family members still there, waving and taking photographs, as the bus prepared to pull away. Their son worked his way to a seat. The parents reached up and pressed their hands against the glass, where their son’s narrow face was framed by the window.

Crookston had prepared himself for this emotional goodbye, and for the fear and uncertainty ahead. He was trusting now in his religious faith, and his family’s support, to help him persevere.

“We’re going over; we will be receiving contact,” he said not long before he left. “Someone is definitely not coming back. One way or another, there’s going to be death. . . . It’s just the way things are.”

david.zucchino@latimes.com