Marine recruits from Platoon 2103 march in a ceremony during which they are each awarded the eagle, globe and anchor - the official emblem of the United States Marine Corps. (Rick Loomis / Los Angeles Times / September 15, 2007)

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

CAMP PENDLETON - A Marine recruit stumbled from the ranks and collapsed on a dirt trail. A corpsman, her medical bag bouncing in the dust, hustled over to the fallen man. The recruit was bathed in sweat, his face clammy and sickly green.

As the troop column marched on, the drill instructor cried out, "Here comes the silver bullet!"

The recruit was about to receive the ultimate indignity -- a shiny rectal thermometer to check his body temperature. It happened on the trail for all to see: Pants down. Buttocks bared.

The column kept moving.

It was the final day of the Crucible, a three-day ordeal in the harsh, scrubby foothills of Camp Pendleton. If a recruit survives the Crucible, the midpoint of the 13-week boot camp, he will likely survive to graduation.

Seven weeks earlier, three friends from Santa Clarita, just 110 miles north but a world away, arrived as eager recruits. Teenagers Daniel Motamedi, Daryl Crookston and Steven Dellinger signed up for the buddy program, which put them in the same boot camp platoon.

Now, the three friends -- their faces streaked with camouflage paint and grime -- were on the Crucible's biggest physical challenge, a 10-mile hike called the Reaper. Recruits prefer to call it the "hump" or the "death march."

Their uniforms gave off the sour stench of stale sweat. They had slept only a few hours over the previous two days, crammed into two-man tents. They had been allowed just three military Meals Ready to Eat.

Their thighs burned. Their spines ached under their 65-pound packs. Their M-16 rifles clanked against their sides. They gulped water from canteens as they struggled to stay in step. They screamed out on cue: "One shot, one kill! Ready to die, but never will!"

The three recruits, and 80 others in their platoon, had by now been hammered into obedience by omnipresent drill instructors. The friends had each been punished countless times for violations such as marching out of step or inattention to detail. They were forced to do dozens of push-ups, pull-ups or sit-ups. Drill instructors call it "incentive training." Recruits call it "getting slayed."

The friends had anticipated all that. They hadn't anticipated getting sick.

Steven, 18, developed an ear infection and pneumonia. Daryl, 18, contracted flu and pinkeye. Daniel, 17, had pneumonia, followed by oral surgery to remove impacted wisdom teeth, then a nagging thigh bone injury. All three contracted upper respiratory infections, coughing and hacking along with others in their tight barracks warren.

"Recruit crud," said their senior drill instructor, Staff Sgt. Nicholas Hibbs, with a shrug. "Everybody gets a little bit sick."

The three resisted sick call. Too much sick time could get a recruit dropped.

The platoon's BDR -- basic daily routine -- was unrelenting: Reveille and out of bed at 5 a.m. Ten minutes to stretch, wash up, fill canteens.

Every minute was prescribed: classes, exercises, drills, physical fitness. The recruits tore through each day, from day T-1 (introductory physical training) to day T-18 (confidence course). They endured day T-37, a gas chamber ordeal in which they inhaled tear gas.

They fired live ammo, fought with pugil sticks and bayonets, and learned Corps history, first aid, how to land blows and how to counter them. They rotated into fire watch. Every night, the recruits sang a verse of the Marines' Hymn. For five minutes, they prayed. At 9 p.m., it was taps and lights out.

All this for $1,458 a month.