But not yet. Marine infantry units have traditionally been nonpolitical, to the point of stubbornly embracing a peculiar detachment from policy currents at home. It is a pillar of the corps’ martial culture: those with the most at stake are among the least involved in the decisions that send them where they go.

Image Sgt. Michael A. McKinnon talked with Mr. Menti on Wednesday. Credit... Joao Silva for The New York Times

Mr. Rumsfeld may have become one of the war’s most polarizing figures at home. But among these young marines slogging through the war in Anbar Province, he appeared to mean almost nothing. If he was another casualty, they had seen worse.

“Rumsfeld is the secretary of defense,” Sergeant McKinnon said, answering Lance Corporal Davis’s question.

Lance Corporal Davis simply cursed.

It did not sound like anger or disgust. It seemed instead to be an exclamation about the irrelevance of the news. The sergeant might as well have told the squad of yesterday’s weather.

Another marine, Lance Cpl. Patrick S. Maguire, said the decisions that mattered here, inside Company F, Second Battalion, Eighth Marines, were much more important to them than those made in the Pentagon back home.

There are daily, dangerous questions: When to go on patrol, when to come back, which route to take down a road, which weapon to carry, and, at this moment, which watch each marine would stand, crouched up on the roof, in the cold wind, exposed to sniper fire.

His grandfather fought at Iwo Jima, he said, and his father was a marine in Vietnam. This was his second tour in Iraq. “Here’s the deal,” he said. “Someone points a finger at you, and you go.”