In the war on wildfire, California turns to the military

James Nelson deployed to Iraq in 2004 as an artilleryman with the Army. He saw fierce fighting and lost close friends during his one-year tour, and when he reflects on the experience, he wonders what the war achieved.

Fifteen years later, Mr. Nelson, now a sergeant first class in the California National Guard, has deployed to the Sierra Nevada foothills about 50 miles north of the state capital of Sacramento. Beneath a canopy of ponderosa and sugar pines, Douglas firs, and black oaks, he and 20 other soldiers work to remove underbrush and dead trees, assisting state crews to thin forests of the fuel that feeds wildfires. He describes the mission as more purposeful than his combat tour.

“Over there in Iraq, you’re protecting each other, but it’s hard to see where you’re making a difference,” Mr. Nelson says. “Here you can see cause and effect. It feels like we’re accomplishing something.”

He talked on a recent morning over the high whine of chainsaws and a wood chipper’s guttural thudding. On a leaf-strewn slope