Todd Heisler, a New York Times staff photographer, worked with the reporter Dave Philipps on a report about suicides in the Second Battalion, Seventh Marine Regiment. In 2008, the 2/7 deployed to a wild swath of Helmand Province in Afghanistan and suffered more casualties than any other Marine battalion that year. Below, Mr. Heisler recounts his experiences during the reporting of the article.

Noel Guerrero’s alarm goes off at 4 a.m. He springs to his feet and immediately starts working out in the darkness of his living room as his wife and son sleep in the other room. He sleeps on the couch because he still has nightmares. Since Afghanistan, he has developed an obsession to details. He runs marathons and keeps a log that includes, among other things, his daily tasks, caloric intake and heart rate, which he checks several times a day.

In 2008, his unit, the Second Battalion, Seventh Marine Regiment, suffered more casualties during eight months in a remote part of Helmand Province than any other Marine battalion that year. They saw combat almost daily. Now, roughly seven years later, suicides are spreading through the unit. There have been 13 since 2008.

To explain the story of the 2/7 Marines, the reporter Dave Philipps showed me a bubble diagram he sketched on a worn sheet of yellow legal paper that showed how the Marines were entwined — those who died in combat, those who died at home, those who attempted suicide. Tangles of lines connected them by a bad firefight or some other traumatic event. Multiple sheets had been taped together as he amended his reporting.

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Mr. Philipps spent months earning the trust of a few of the Marines from the unit, and over time, more opened up. By the time I signed on to the project, Mr. Philipps had met the men at the heart of it. Those who were living, but were surrounded by death. They were the story.

Noel Guerrero is one of those men. One night, he swallowed a bunch of pills in an attempt to take his own life. Manny Bojorquez, a close friend and fellow 2/7 Marine who lives hours away, called the police when he could not reach Mr. Guerrero. He saved Mr. Guerrero’s life at the risk of their friendship. But he says it was worth it.

Because they are no longer active members of the military, they fall into a large crevasse between two bureaucracies. Statistics about their suicides are hard to come by as the military and the Department of Veterans Affairs do not share information that could allow the monitoring of units over time.

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Most service members, especially grunts — those in the infantry — feel as if very few people get what they have been through. From the previous work I’ve done with the military, I learned that it is important not to sensationalize the situation or go in with preconceived notions of what the photographs should be. That doesn’t mean I don’t have an idea of situations I’d like to be there for. But I’m trying to photograph something you can’t really see. Grief and trauma manifest in so many ways. So I just try to hang out as much as possible, looking for subtle cues to paint an emotional portrait.

I spent a few days with Mr. Guerrero, following him as he went about his daily routines. One evening, as we returned from a gathering at his church, he pulled his car into the garage and I noticed a garment bag hanging in the corner. He unzipped the bag to show me his dress blues, a row of medals pinned across the breast. It’s where he keeps his Purple Heart, he said. Tucked away in the garage.

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