HUNTER GARTH was in a gunfight for his life — and about to lose.

He and seven other Marines were huddled in a mud hut, their only refuge after they walked into an ambush in Trek Nawa, a Taliban stronghold in Afghanistan. Down to his last 15 bullets, one buddy already terribly wounded, Mr. Garth pulled off his helmet, smoked a cheap Afghan cigarette, and “came to terms with what was happening.”

“I’m going to die here with my best friends,” he recalled thinking.

I didn’t know any of this — nor the remarkable story of his survival that day — when I met him two months ago in Colorado while reporting for an article about the marijuana industry, for which Mr. Garth and his company provide security. But I did know he was a vet and so I did what seemed natural: I thanked him for his service.

“No problem,” he said.

It wasn’t true. There was a problem. I could see it from the way he looked down. And I could see it on the faces of some of the other vets who work with Mr. Garth when I thanked them too. What gives, I asked? Who doesn’t want to be thanked for their military service?

Many people, it turns out. Mike Freedman, a Green Beret, calls it the “thank you for your service phenomenon.” To some recent vets — by no stretch all of them — the thanks comes across as shallow, disconnected, a reflexive offering from people who, while meaning well, have no clue what soldiers did over there or what motivated them to go, and who would never have gone themselves nor sent their own sons and daughters.