Mr. Fay worries that this setup, along with the program’s diminished size, could lead to its falling off the top brass’s radar, a development that could threaten what he and other supporters see as an important part of the Marine Corps identity.

(Lin Ezell, the civilian director of the museum, said her staff is now searching for a replacement for Mr. Fay and “thinking about ways that we might expand the program,” though she declined to elaborate. At a time when Congress is likely to pare back the budget as the war winds down, she said, “it’s not a good time to be talking about expansion.”)

“The Marine Corps is more like a tribe than some corporate organization,” Mr. Fay said. “And the combat art program, we’re like the shamans. We’re the ones who take this experience and try to articulate it.”

In the Quantico warehouse, which serves as Sergeant Battles’s studio, the two men were surrounded by the sergeant’s most recent work. (Mr. Fay moved out of the building when he retired.) Many of the paintings explore the Marine experience from a disarmingly humanistic perspective: a boy perching in a leafy tree near Carrefour, Haiti, where Sergeant Battles deployed last February to cover humanitarian relief efforts; Marines snoozing by piles of body armor in Helmand Province, Afghanistan, in 2009. A painting from his 2007 Iraq tour presents a half-smiling woman carrying a toddler, a luminous, enigmatic image that brings the Belgian artist Luc Tuymans to mind.

One thing that sets the Marine Corps program apart from those of other services is its focus on human subjects and experiences. That’s what has always appealed to Anita Blair, chief strategist at the National Security Professional Development Integration Office, who got to know the program when she was acting assistant secretary of the Navy for a year (2008-09). “When you go over to the Air Force,” she said, “the art is all airplanes. In the Navy it’s all ships. Army art tends to be more about the battle, and the Army loves trucks. They’re fixated on vehicles. But the Marine Corps is fixated on Marines.”

A bigger difference, though, may be the program’s requirement that members be both Marines and full-fledged artists, not one or the other. (In the Vietnam War, however, it used civilian artists too.) When deployed, they carry the same 75 to 100 pounds of combat gear  including food and water, body armor, a Kevlar helmet, an M-16, a 9-millimeter pistol and ammunition  as their fellows, as well as art supplies. Also, said Joan Thomas, the art curator at the Marine Corps museum, they must be vetted by her and by artists who preceded them in the program.