Alpharetta, Georgia (CNN) -- His ramrod straight posture and slicked-back buzz cut give it away. Steve Venable is a boot camp veteran.
But today, he's drilling his rookies for perhaps the most challenging mission of their lives: fatherhood.
One by one, an army of expectant dads files into Venable's classroom at Northside Hospital near Atlanta, hoping to gain some wisdom from the ex-Marine-turned-"daddy boot camp" instructor.
Stephen Goodnough arrived 20 minutes early, admittedly tense. His baby girl is due in less than a month.
"I've never babysat, I've never taken care of a child, so that's probably why I've been nervous," he said.
Goodnough has the crib, the nursery, the bottles and the bibs. But he hasn't a clue about what to actually do with the baby.
"It's not like they're power tools," said Goodnough, a marketing manager for NAPA auto parts. "They don't come with instruction manuals. It's a kid, a human life. ... You leave the hospital, and that's it."
He's among some 300,000 expectant dads who have turned to Boot Camp for New Dads, a program now in 45 states as well as Britain, Canada, Italy and Japan.
The course started in 1990 near a Marine base in California, and has grown despite declining attendance in childbirth classes nationwide as more parents turn to the Internet.
Boot camps now take place everywhere from affluent communities to low-income neighborhoods and even a prison in Ohio.
"I'd say it's more important in low-income communities. The role models have more impact there," said Greg Bishop, founder of Boot Camp for New Dads.
In three hours, the men in this boot camp learn a battery of "troubleshooting and diagnostics," including how to swaddle and soothe a crying baby, change a loaded diaper and deal with the mother during and after pregnancy.
Bob Meecham's baby isn't due until January 29, but the anxiety is already evident on his face.
"I know what I'm most scared of. I'm most scared of 4 a.m. in the morning, and the baby not being able to stop crying for two hours. What do you do?"
With 10 men surrounding a brightly colored mat and blanket on the floor, Venable, a father of two, issues a disclaimer:
"I'm not a doctor. I don't play one on TV, and I didn't stay in a hotel last night. I'm just a dude," the instructor said.
His assistant today is 1-month-old Anabella, daughter of recent boot camp graduate John Riley.
Within minutes, Anabella morphed from smiling and tranquil to irritated and screaming.
"You've got a set of lungs on you," Venable said as he lay her down on the blanket.
After a few swift motions with the cloth, Venable picked up the tightly wrapped infant and held her on her side, parallel to his chest.
"SHHH," he blew loudly across her cheek.
Less than six seconds later, wailing Anabella fell silent in Venable's sturdy arms.
"It's like magic!" one rookie exclaimed.
In addition to hands-on demonstrations and training, in this room, no subject is off limits. Females over 2 feet tall are not allowed, so men can share their concerns freely -- particularly about how to handle their mates.
"This class was my idea because I wanted something to help me learn to deal with her," Meecham said, echoing other husbands' concerns about their wives. "She's going through a lot."
Venable addresses a variety of mother-related topics, including how to help during labor, how to spot signs of postpartum depression and how to gain her trust as a caretaker.
"The biggest challenge the dad has is establishing enough credibility so that mom will relinquish control," he said. "If you don't have the hands-on skills, and you don't have knowledge of the (baby's) cues ... it will be very hard to come to any kind of arrangement and have any kind of credibility. Those who don't have those skills tend to get treated as secondary parents. They'll feel sort of left out."
He said other topics men often reserve for boot camp include sex, discomfort with changing diapers and finances.
Venable, who spent four years in the Marines, is among a network of experienced dads who have graduated from daddy boot camp and have come back as instructors.
"People who know me think it's either absolutely odd or encouraging that I'm doing this on my off time," Venable said.
But there are parallels between the Marines and daddy boot camp, he said.
"When you look at military people, they look at critical skill sets. Once they learn what those skill sets are, they practice, practice, practice until they perfect them."
He said the same holds true for quieting a bawling baby by swaddling, or wrapping a baby snugly in a blanket to mimic the feeling inside the womb.
Riley, Anabella's father, said he also returned to boot camp to help pay forward what he learned.
"It was such a help for me, I knew if I brought her in it would help everyone else," the executive search firm owner said.
Dressed in a crisp white shirt and stylish watch, Riley looks more prepared for business than a daddy boot camp, until you see the pink Snoopy blanket in tow.
He said he didn't expect to be such a hands-on father, figuring he'd primarily work while his wife took care of most baby issues.
"Once I had the baby, that completely changed my perspective on everything," he said. "I love it, she's so much fun. It's more work than I expected, but anytime I look at her face, it relieves all my problems."
Before long, Anabella produced her second dirty diaper of the class.
"OK -- next victim," Venable said.
A few groans sounded across the room as Meecham stepped up to the plate, cautiously removing a loaded diaper for the first time.
"I was like, oh man, don't twist the baby's ankle, make sure you get it clean all the way around," he said.
By the end of the boot camp, Meecham also learned how to feed Anabella. After a mild struggle to get the bottle in her mouth, his trepidation about fatherhood seemed to melt away.
"I got a little warm and mushy inside," he said. "Baby papa syndrome kicked in, and I was like, yeah, this is going to be my kid soon."