This report is part of "Those Who Serve," an occasional series that looks at those who wear the military uniform during a time of war.
It's early afternoon at a small outpost in eastern Afghanistan, and U.S. Army Sgt. Chris Cunningham, with the 10th Mountain Division, heads into a long, dusty tent to teach Afghan soldiers the basics of map reading.
After the sun sets, American soldiers help Afghan soldiers outside the wire. They pop artillery shells containing what's called an illumination round.
It transforms the desert night into garish midday and with luck scatters any Taliban near Afghan checkpoints.
Now, it's late night, and Cunningham stares into the flames of a fire pit. On his fifth deployment to Afghanistan, the sergeant has survived some of the most horrific fighting of the past decade.
He puffs on a cigar and recalls the names of friends he lost in his first firefight, more than a decade ago: Brad Crose, Matthew Commons, Marc Anderson.
"[Anderson] was awesome," Cunningham says. "He was a math teacher before he became a Ranger. His dad was a Ranger in Vietnam."
Cunningham didn't seem destined for this kind of life. He worked in a restaurant in his native Vermont as a dishwasher and later a cook. He wanted to do something different.
Combat was definitely different. In March 2002, his first deployment sent him to the mountains hard against the Pakistan border, where he took part in Operation Anaconda, one of the first large-scale battles of the Afghan war.
Cunningham's team climbed into a lumbering Chinook helicopter. He recalls flying high into the hills, seeing the patches of snow stream past the windows.
"I don't think I was really nervous. I was excited, excited to do it. I think we were all excited to do it," he recalls. "All the training in Kentucky and South Carolina and Georgia. We were finally going to do our mission."
Their mission was to support a group of Navy SEALs battling a Taliban force. But their helicopter came under fire and crash landed. The soldiers streamed out into a gunfight.
"The boys did what they were supposed to do," Cunningham says. "They died getting off the helicopter. They died within seconds."
There are no more firefights for Cunningham. No more seeing his friends placed in body bags. No more helping young soldiers cope with the horrors of war.
Now, Cunningham is in something of a safe haven inside a combat outpost in Ghazni province.
He admits he was not happy when he heard about this training job with the Afghan army, or ANA. "I was nervous because I knew the ANA before," he explains. "They aren't anything like they are now. They were undisciplined and lazy."
But he says he has been impressed with their development, their willingness to take on the Taliban, and their eagerness to learn about what they'll face.
Cunningham recalls a conversation with one of the Afghan staff sergeants he has trained. "He says, 'Have you lost a soldier?' I said, 'Yes.' 'Can you tell me what it's like?' " Cunningham says.
"That's why it's important to train. Because you can't be complacent," he says. "That's when the enemy attacks. Always be ready out there."
He estimates that he has lost 20 friends to the Afghan war, friends like Sgt. Jared Monti, who died trying to save a fellow soldier and was awarded the Medal of Honor. That day, Monti crawled out under Taliban fire to save a wounded soldier. He was struck himself, and called out to Cunningham, "Cunny, come get me."
"I said, all right, roger that. And told the guys to cover me. And started bear crawling over there," Cunningham says.
But he couldn't reach Monti; there were too many bullets.
"He said, 'Tell my family I'm at peace with God.' And then he died," Cunningham says.
For Cunningham, there is no more excitement about war. It's been replaced by a sort of grim wisdom and the heavy responsibility of training soldiers and honoring those who died in Afghanistan.
It's as if they're "looking over us," he says.
"And you have to pass on what they taught. That will help them live forever," Cunningham says. "Whatever they taught you, you teach to others and it keeps going."
He has his own family to look after now: a wife and two young children, Cecilia who turned 1 on this deployment and 4-year-old Hudson.
"[Hudson] doesn't understand what we do," Cunningham says. "I bought him a globe over here, a globe and a magnifying glass. He knows where Afghanistan is now. He knows why Daddy can't come home right now. He knows I've got to take care of soldiers."
Sgt. Chris Cunningham has several months before his fifth tour is over, and he gets to head home.